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In this work, a hollow tubule Bi 0.8 Ca 0.2 FeO 3– δ (BCF-T) cathode was synthesized using the metal nitrate impregnation method, with absorbent cotton serving as the template. The phase composition, electrocatalytic activity performance, oxygen reduction reaction (ORR) processes, and CO 2 tolerance of the BCF-T cathode are systematically studied. Compared with ordinary powder BCF (BCF–P) cathode, the BCF-T cathode presents outstanding electrocatalytic activity for ORR. The polarization resistance of the BCF-T cathode is 0.06 Ω cm2 at 700 °C, and the peak power density (PPD) of the single cell is 1042 mW cm−2 at 800 °C. The unique tubular microstructure of BCF-T is beneficial for enhance the oxygen transport property and the ORR activity of the electrode. Moreover, the BCF-T electrode also shows excellent CO 2 tolerance and chemical stability after 10% CO 2 treatment at 700 °C for 10 h. These features indicates that the tubule electrode with superior electrocatalytic activity and CO 2 tolerance might provide an effective strategy to design promising cathode catalysts for SOFCs. • A hollow tubule Bi 0.8 Ca 0.2 FeO 3- δ (BCF-T) cathodes are developed for SOFCs. • The polarization resistance of the BCF-T cathode is 0.06 Ω cm2 at 700 °C. • Maximum power density of single cell with BCF-T cathode reaches 1042 mW cm−2 at 800 °C. • BCF-T cathode shows outstanding CO 2 tolerance and chemical stability. [ABSTRACT FROM AUTHOR]

The energy crisis stems from increasing demand, diminishing fossil fuel reserves, and insufficient investment in renewable alternatives, posing a profound threat to global energy security and environmental sustainability. Fuel cells offer promise as a solution to the energy crisis and the integration of two-dimensional carbon materials in fuel cell catalysts holds potential for enhancing efficiency, reducing costs, and improving the overall sustainability of fuel cell technologies. The new two-dimensional carbon form tetra-penta-octagonal-graphene and its boron doped derivative have been examined in this report for its applicability in the electrocatalytic oxygen reduction reaction for generation of electricity. The most favorable site for the reaction in the pristine specimen and the most favorable boron doping site have been carefully determined based on adsorption energy and formation energy, respectively. Projected density of states confirms a low density of states for the active site in both specimens. Boron doping causes a significant charge transfer from the primed site. The analysis of the four electron pathways along with the dioxygen adsorption step in the acidic medium has been conducted to gain a deeper understanding of the process. In both systems, the formation of the *O intermediate is associated with the highest Gibbs free energy change. The performance of the pristine material in the process has been found to support monotonically exothermic reaction with an overpotential of 0.622 V whereas the boron doped specimen presents very small barrier for the dioxygen adsorption step followed by monotonically exothermic reaction steps with overpotential 0.549 V. • A new sp2 stable 2D carbon allotrope TPO-graphene shows electrocatalytic activity. • Active site has lowest partial density of states at Fermi level. • Steps of ORR in four-electron pathway in acidic medium are monotonically exothermic. • TPO-graphene has a overpotential of 0.622 V for the ORR process. • Boron doping creates ORR catalysis site with lowest partial density of states. • Boron doped TPO-graphene has a overpotential of 0.549 V for the ORR process. [ABSTRACT FROM AUTHOR]

Strain engineering is a promising approach to control the oxygen reduction reaction (ORR) kinetics of perovskite cathodes in solid oxide fuel cells (SOFCs). For multi-component oxide materials such as perovskite, there are two main strain effects: altering the surface reactivity and modifying the surface chemical composition. Our previous study (Energy Environ. Sci. 11 (2018) 71–77) showed that applying tensile strain enhances the oxygen exchange kinetics on SrTiFeO 3−δ (STF) surfaces by suppressing Sr segregation. However, the potential impact of changes in surface reactivity by strain on the oxygen exchange kinetics of STF remains unexplored yet. To address this gap, density functional theory (DFT) calculations are performed to evaluate the strain effect on oxygen incorporation on SrO and (Ti,Fe)O 2 (001) terminations of STF surfaces. The presence of surface vacancies is necessary for O 2 activation and dissociation. With the assistance of oxygen vacancies, O 2 incorporation is favorable on the (Ti,Fe)O 2 surface over the SrO surface. Tensile strain facilitates O 2 incorporation kinetics on the (Ti,Fe)O 2 surface, but its effect is weak on the SrO surface. Our results demonstrate that the enhanced oxygen surface exchange kinetics due to tensile strain in STF result not only from the inhibition of Sr segregation but also from an increase in O 2 incorporation. [Display omitted] • DFT study of O 2 incorporation on two terminated surfaces of SrTiFeO 3 (001). • Surface V O are vital for O 2 incorporation on both (Ti,Fe)O 2 and SrO surfaces. • Biaxial strain boosts O 2 incorporation on (Ti,Fe)O 2 , minimally affecting SrO. • This work elucidates the experimentally observed link between strain and surface oxygen exchange. [ABSTRACT FROM AUTHOR]

The current study describes a facile, time-effective and cost-viable synthesis of highly efficient Fe–N–C catalysts tailored for PEMFC. In this work, three different Fe–N–C catalysts for oxygen reduction reaction (ORR) have been synthesized by pyrolyzing different organic molecules in a microwave machine. The catalytic materials have been characterized using advanced techniques such as SEM, TEM, EDS, XPS, and BET analysis to elucidate their morphological, compositional, and surface properties. The fabricated materials i.e. Fe–N–C-Urea (Fe–N–C–U), Fe–N–C- Para- Phenylene Diamine (Fe–N–C- p PD) and Fe–N–C-5-Amino-1-(4′-Aminophenyl)-1,3,3-Trimethylindane (Fe–N–C-AAT) exhibit remarkable peak power densities, reaching as high as 0.96 W cm−2, 0.77 W cm−2 and 0.90 W cm−2, respectively, at a flow rate of 0.4 L min−1 of oxygen and 0.2 L min−1 of hydrogen, keeping the temperature constant at 80 °C. The current work emphasizes the deployment of facile and rapid synthetic protocol coupled with exploiting ingenious organic molecules and avoiding the application of any solvent. [Display omitted] • Adopt microwave-assisted pyrolysis strategy to synthesize distinct Fe–N–C electrocatalysts. • Fe–N–C–U and Fe–N–C-AAT exhibits eminent ORR activity in acidic medium. • The power density of Fe–N–C–U and Fe–N–C-AAT based PEMFC reaches 0.96 and 0.90 W cm−2, respectively. [ABSTRACT FROM AUTHOR]

A-site doping with Ca2+, Sr2+ for the cobalt-free BaFeO 3-δ -based cathode materials for proton-conducting ceramic fuel cells (PCFCs) is studied. The composite Ba 0·8 Ca 0·2 FeO 3-δ (BCF0.2)-BaZr 0.1 Ce 0·7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) and Ba 0·8 Sr 0·2 FeO 3-δ (BSF0.2)-BZCYYb electrode show polarization resistance (R p) of 0.156 Ω cm2 and 0.308 Ω cm2 at 700 °C, respectively. It is found that the Ca or Sr doping not only benefits oxygen vacancy formation and ion migration but also optimizes the surface oxygen reduction reaction (ORR) process. The density functional theory (DFT) calculations show that the Gibbs energies of *OOH and *OH intermediates are decreased, indicating an enhanced surface ORR. The PCFC with BCF0.2-BZCYYb composite cathode achieves the maximum power density of 299.75 mW cm−2 at 700 °C and shows good stability at 650 °C for 65 h under a constant voltage of 0.75 V. These findings suggest that the BCF0.2-BZCYYb has the potential to serve as cobalt-free cathode materials for PCFCs. [Display omitted] • Cobalt-free cubic perovskite Ba 1-x A x FeO 3-δ (A = Ca, Sr) materials are synthesized. • The Ba 0·8 Ca 0·2 FeO 3-δ -BZCYYb symmetrical cell shows low R p of 0.156 Ω cm2 at 700 °C. • DFT calculation reveals the ORR information on BaFeO 3-δ (110) surface doped with Ca or Sr. • The Gibbs energies of *OH and *OOH intermediates are decreased. [ABSTRACT FROM AUTHOR]

The non-noble bimetallic oxides have recently received more and more attention in electrocatalytic oxygen evolution reaction (OER) because of their potential to replace traditional precious metal catalysts, but the low activity and stability limit their wide application. Herein, the bimetallic oxide CoNiO 2 layers are decorated on the nitrogen-doped carbon nanofibers (NCF) through in situ grown of Ni(Co) bimetal organic frameworks (Ni(Co)-MOFs) on polyacrylonitrile nanofibers and subsequent pyrolysis process, so that a new NCF@CoNiO 2 electrocatalyst with one-dimensional (1D) core-shell structure is synthesized by structural induced effect of polyacrylonitrile nanofibers. Importantly, the unique interconnected network formed in the 1D NCF@CoNiO 2 electrocatalyst effectively improves electron mobility and mass transport capacity, thus exhibiting the glorious OER activity and long-term stability in alkaline solutions. As a result, the optimal NCF@CoNiO 2 -7 electrocatalyst requires an overpotential of 518 mV for OER at the current density of 100 mA cm−2, which is obvious lower than that of RuO 2 (633 mV) and CoNiO 2 /C-7 as a contrast sample (569 mV), respectively. This work opens up a new path for structural control of 1D bimetallic oxides to improve OER activity and stability. [Display omitted] • The NCF@CoNiO 2 electrocatalyst with a 1D core-shell structure is exploited. • 1D core-shell structure ascribes to structural induced effect of polymer nanofibers. • The NCF@CoNiO 2 exhibits superior OER activity and stability. • Interconnected network improves electron mobility and mass transport capacity. [ABSTRACT FROM AUTHOR]

Introducing other heteroatom is considered to be a highly effective approach to improve the limited catalytic activity from single nitrogen element doping in nitrogen-doped porous carbon materials. In this work, F and S-modified nitrogen-doped porous carbon (F-S-N-C) is prepared by annealing the assembly material of poly3-fluoro aniline, hydroxyethyl sulfonic acid and g-C 3 N 4 , in which the g-C 3 N 4 is employed as template agent and pore-forming agent. A series of characterization techniques indicate that simultaneous doping of F and the S atoms enhance the electron transfer and construct more defects for N-doped 3D porous carbon, resulting in improved electrocatalytic performance. The prepared F and S-cooperated nitrogen-doped porous carbon (F-S-N-C) exhibits significantly improved oxygen reduction reaction electrocatalytic activity in alkaline media with a half-wave potential of 0.808 V. The zinc-air battery (ZAB) with F-S-N-C as the air cathode catalyst demonstrates a peak power density of 167 mW cm−2, which is higher than that of commercial Pt/C (158 mW cm−2). Moreover, the specific capacity of the F-S-N-C-based ZAB reaches to 817 mAh·g−1. Fluorine and sulfur atoms doped N-doped 3D porous carbon were prepared through one pot method. The best performing electrocatalyst (F-S-N-C) exhibits a half wave potential of 0.808 V in 0.1 M KOH. [Display omitted] • Fluorine and sulfur atoms induced N-doped 3D porous carbon was prepared. • Fluorine and sulfur co-doping promote the generation of abundant active sites. • The zinc air battery with F-S-N-C has high power density and specific capacity. [ABSTRACT FROM AUTHOR]

To replace the noble metal catalysts for oxygen reduction reaction (ORR), a Ni@C-supported N-doped carbon material (Ni@C/NC) is in-situ prepared via one-step pyrolyzing the polymerizable ionic liquid of vinyl imidazole combined with Ni(NO 3) 2. Systemic investigations demonstrate that these nanosized Ni particles are tightly wrapped with a thin carbon layer to form the core/shell structure, meanwhile carbon capsules are synchronously yielded on the carbon matrix. As a result, both the carbon shell and the carbon capsule jointly increase the active sites of the Ni@C/NC, while the carbon shell also contributes the fast electron-transfer from Ni particle. Compared with the normal Ni-supported carbon catalyst, the Ni@C/NC shows the respectable ORR performance with the onset and half-wave potentials of 0.96 and 0.84 V RHE. After the long-term electrocatalysis (10 h), the Ni@C/NC is found to possess the great structural and electrocatalytic stabilities, which maintains 93 % of the initial current density and the well-dispersed and uniform Ni@C particles. Subsequently, a Zn-Air battery with the Ni@C/NC cathode is assembled and exhibits a peak power density of 200 mW cm−2. Therefore, the as-obtained Ni@C/NC with the high electroactivity and stability can be expected as an ideal candidate to apply in the metal-air batteries and fuel cells in the future. Ni particles wrapped with a thin carbon layer is in-situ formed and supported on a N-doped carbon with many capsules, fabricating the Ni@C/NC catalyst, which exhibit the superior catalytic performance for oxygen reduction. [Display omitted] • A Ni@C-supported N-doped carbon material is in-situ prepared. • Nanosized Ni particles are wrapped with a thin carbon layer. • Carbon capsules are synchronously yielded on the carbon matrix. • The Ni@C/NC shows the respectable ORR performance. • The Ni@C/NC possesses the great structural and electrocatalytic stabilities. [ABSTRACT FROM AUTHOR]

Uncovering the origin of bifunctional oxygen reduction/evolution reaction (ORR/OER) activity of M-N-C type electrocatalysts is essential for their extensive usage in fuel cells and metal-air batteries. The electrochemical properties of heterogeneous M-N-C catalysts depend on the surface structure, which can be modified via different synthetic methods. Herein, we investigate the effect of structure on the activity of Co–N–C electrocatalyst material derived from an amorphous metal-organic framework TAL-2. Specifically, TAL-2 served as the sole precursor for the synthesis of a range of Co–N–C catalysts via various carbonization and acid-leaching modes. Co–N–C catalysts were prepared by carbonizing TAL-2 at different temperatures (700, 800, 900, and 1000 °C) and subsequent acid-leaching using different acids, namely HCl, H 2 SO 4 , and HNO 3 , either individually or in various combinations. This resulted in the generation of 36 distinct catalyst samples, each exhibiting unique morphological characteristics. By systematically varying these parameters, we aimed to unravel the intricate relationship between post-synthetic treatment and the resulting electrocatalytic properties, shedding light on the rational design of Co–N–C catalysts for enhanced ORR/OER. [Display omitted] • Co–N–C catalysts were derived from TAL-2 MOF by varied post-synthetic treatment. • 36 unique catalysts were studied to understand structure-activity relationships. • Optimized catalysts showed superior ORR/OER performance with low ΔE values. [ABSTRACT FROM AUTHOR]

Alloying platinum with other 3d transition metals (M) in an organized manner is a proven method to enhance the activity and lifespan of Pt catalysts utilized in proton exchange membrane fuel cells (PEMFC). Herein, a distinct composite has been engineered, featuring structured Pt–Fe intermetallic compounds (L1 2 Pt 3 Fe NPs) supported on an iron-doped sulfur-nitrogen-carbon (Fe-SNC) support. The L1 2 Pt 3 FeNPs function as the primary catalytic core for the oxygen reduction reaction (ORR) instead of the conventional Pt NPs. The sulfur atom on the Fe-SNC can secure L1 2 Pt 3 Fe NPs to prevent their aggregation during elevated temperature and operational phases. Additionally, the presence of S atoms can regulate the electronic configuration of platinum and decrease the bond strength between Pt and oxygen-containing intermediates. Consequently, the L1 2 Pt 3 Fe/Fe-SNC catalyst demonstrates exceptional catalytic efficiency and longevity for ORR with E 1/2 of 0.911 V as well as a mass activity (MA) of 0.47 A/mg Pt. The L1 2 Pt 3 Fe/Fe-SNC maintains outstanding ORR stability (MA form 0.47 A/mg Pt to 0.38 A/mg Pt) after 30,000 cycles of AST. Impressively, the L1 2 Pt 3 Fe/Fe-SNC has a power density of 1.547 W/cm2·H 2 –O 2 and 0.669 W/cm2·H 2 -Air at 0.4 V (cathode Pt loading: 0.04mg Pt /cm2) better than commercial Pt/C in PEMFC single-cell. This work provides new ideas for constructing various PtM intermetallic catalysts. [Display omitted] • L1 2 Pt 3 Fe emerges as a major catalytic core for oxygen reduction reactions. • Synergistic effect between L1 2 Pt 3 Fe and Fe-SNC enhances the catalytic activity. • S atoms can anchor L1 2 Pt 3 Fe to enhance catalytic stability. • L1 2 Pt 3 Fe/Fe-SNC shows great ORR performance in PEMFC. [ABSTRACT FROM AUTHOR]

The Co-based perovskite of SrNb 0.1 Co 0.7 Fe 0.2 O 3-δ (SNCF) stands out for its high intrinsic catalytic activity toward the oxygen evolution reaction (OER) in the alkaline solution. However, the low catalytic activity of SNCF toward the oxygen reduction reaction (ORR) restricts its application in the zinc-air batteries (ZABs). To address this issue, we develop the oxygen vacancy enriched heterostructure (SNCF–NF–Co 3 O 4 @N 2) including the SNCF nanofibers with the diameter of 80 nm and Co 3 O 4 nanoparticles anchored on the SNCF surface by electrospinning and sintering in N 2. Due to the high charge/reactant transfer rate, Co3+/Co2+ ratio and oxygen vacancy concentration, SNCF-NF-Co 3 O 4 @N 2 demonstrates the superior bifunctional oxygen catalytic activity. Specially, the ORR half-wave potential can reach 0.69 V, and the OER potential at 10 mA cm−2 is as low as 1.57 V. Remarkably, the aqueous and solid-state ZABs with SNCF-NF-Co 3 O 4 @N 2 exhibit the high peak power densities of 181.2 and 73.3 mW cm−2, respectively. Furthermore, SNCF-NF-Co 3 O 4 @N 2 based ZAB demonstrates an impressive energy efficiency of 79.6%. This study introduces an innovative strategy for enhancing the bifunctional oxygen catalytic performances of Co-based perovskites. [Display omitted] • SNCF-NF-Co 3 O 4 @N 2 heterostructure is prepared by electrospinning followed by sintering in N 2. • SNCF-NF-Co 3 O 4 @N 2 has the abundant oxygen vacancies and high Co3+/Co2+ ratio. • SNCF-NF-Co 3 O 4 @N 2 demonstrates the superior ORR/OER catalytic activities and stabilities. • The ZABs with SNCF-NF-Co 3 O 4 @N 2 show the high reversibility and cycling stability. [ABSTRACT FROM AUTHOR]

Oxides with the same structure as K 2 NiF 4 have received increasing interest in reversible solid oxide cells (RSOCs) because of the unique advantages of low thermal expansion efficient (TEC), fast oxygen exchange kinetics, and high chemical stability. Herein, Fe-doped Nd 0.8 Sr 1.2 Ni 1-x Fe x O 4±δ (x = 0, 0.15, 0.3, 0.45, NSNF) oxygen electrodes with fast oxygen reduction/evolution reactions (ORR/OER) kinetics are reported. The optimal composition of NSNF is found to be NSNF45 (x equals to 0.45) and the best ratio of NSNF45 to GDC is 6:4 by the mass ratio, delivering a low polarization resistance of 0.067 Ω cm2 at 800 °C. The RSOC with Co-free NSNF45-GDC (6:4) composite oxygen electrode achieves a high peak power density of 1.33 W cm−2 and a favorable electrolysis current density of 1.39 A cm−2 at 1.32 V with 50% steam concentration at 800 °C. Additionally, the reversible cycling between fuel cell and electrolysis modes at 700 °C and the thermal cycling between 700 °C and 300 °C show excellent stability over four hundred hours. The results indicate that composite NSNF45-GDC can be utilized as a promising oxygen electrode material for RSOCs. • A series of Nd 0.8 Sr 1.2 Ni 1-x Fe x O 4±δ are synthesized and evaluated. • The optimal NSNF45-GDC composite shows a R p of 0.067 Ω cm2 at 800 °C. • The cell show good electrochemical performance in both FC and EC modes. • High stability is demonstrated after the reversible cycling and thermal cycling test. [ABSTRACT FROM AUTHOR]

Asymmetric metalloporphyrins are potential electrocatalysts to construct composites for efficient oxygen reduction reactions (ORRs) due to their inherent large dipole moment, which facilitates the charge separation. To find more effective molecular structures towards the ORRs, in particular their performance and electrolyte relationship, we rationally designed two A3B-type asymmetric cobalt porphyrin aPh-TCoP and aBA-TCoP with phenyl and benzoic acid as substituents, respectively. The ORR performance of the porphyrin-decorated carbon black composites was examined in five electrolytes at different pH values spanning from 0.7 to 13.7. It was found that aBA-TCoP/C exhibited better ORR activity and selectivity than aPh-TCoP/C in all solutions. Interestingly, both composites demonstrated their highest ORR activity in the pH13.7 electrolyte and exhibited 4-electron selectivity in the pH3.7 solution. This conclusion is drawn from a comprehensive analysis of various electrochemical properties, encompassing current density, reduction potentials, electron transfer numbers, and intermediate yields. The results illustrate the regulation of ORR properties by altering the electrolyte pH and a notable improvement in the ORR performance through the modification of porphyrin substituents. These findings offer a foundational understanding for the design of efficient metalloporphyrins and the attainment of controlled oxygen reduction in electrochemical devices. [Display omitted] • A3B-type asymmetric cobalt porphyrins are designed for oxygen reduction. • Molecular electronic structures are calculated using density functional theory. • A universal pH range is used to examine the ORR properties. • Greater ORR performance is achieved by aBA-TCoP/C than aPh-TCoP/C. • Both composites exhibit the best activity at pH13.7 and 4-electron selectivity at pH3.7. [ABSTRACT FROM AUTHOR]

Photogenerated carriers transfer and separation from the substance itself to produce spatial isolated electron-hole pairs is crucial for the utilization of composite photocatalysts in the field of photocatalytic hydrogen (H 2) evolution. Herein, novel oxygen-doped porous graphitic carbon nitride (g-C 3 N 4) micro-sheets decorated with Ag 2 MoO 4 have been fabricated by a facile calcination method followed by in situ deposition strategy. The physicochemical properties of the obtained Ag 2 MoO 4 /OC 3 N 4 composites were characterized via SEM, TEM, EDS, XRD, N 2 adsorption-desorption, XPS, UV–vis DRS, PL, transient photocurrent response, and EIS, as well as DFT calculation. In addition, the effects of Ag 2 MoO 4 content, type of scavengers, pH value of reaction solution and dosage of scavenger on photocatalytic H 2 production were investigated. The results show that the modification of ammonium acetate thermal polymerization with urea could enhance the porosity of g-C 3 N 4 and its specific surface area. The Ag 2 MoO 4 nanoparticles are highly dispersed on the OC 3 N 4 surface, reducing the charge transfer resistance at their interfaces. The OC 3 N 4 photocatalyst achieves H 2 yield of 8629.11 μmol/g over 2 h, which is about 1.46 times higher than that of C 3 N 4. The H 2 production amount over the optimal Ag 2 MoO 4 /OC 3 N 4 composite photocatalyst (50 mg) is further enhanced to 16619 μmol/g, which is 1.93 and 180 times higher than that of OC 3 N 4 and Ag 2 MoO 4 , respectively. The S-scheme charge transfer mechanism of Ag 2 MoO 4 /OC 3 N 4 is proposed based on the DFT calculation. This work provides a facile and easy strategy to develop g–C 3 N 4 –based photocatalysts through adjusting chemical composition and photocatalytic properties. [Display omitted] • Oxygen-doped porous g-C 3 N 4 decorated with Ag 2 MoO 4 was fabricated. • Elemental sliver was generated in the photocatalytic H 2 evolution process. • Ag 2 MoO 4 /OC 3 N 4 /Pt system exhibited an excellent performance of H 2 evolution. • Construction of S-scheme mode improved the separation and transfer of carriers. [ABSTRACT FROM AUTHOR]

Metallic aerogels (MAs) with self-supporting three-dimensional (3D) porous structures constitute a potential platform for the construction of robust catalysts. In this work, we successfully constructed 3D PdAu MAs with the optimized d-band electron of Pd and geometrical lattice expansion using a maneuverable in-situ seed-mediated strategy at room temperature. The introduction of Au accelerated the kinetics of Pd 4 Au 3 MAs toward oxygen reduction reaction (ORR), ethylene glycol oxidation reaction (EGOR), and ethanol oxidation reaction (EOR) in alkaline electrolyte, boosting the activity and stability of Pd 4 Au 3 MAs. The mass activities of Pd 4 Au 3 MAs/C in ORR, EGOR and EOR were 1.74, 8.57, and 9.54 A mg Pd −1, respectively, which were remarkably better than those of referenced Pd MAs/C, commercial Pt/C and Pd/C. The rotating ring-disk electrode measurement illustrated that Pd 4 Au 3 MAs/C achieved a 4-electron transfer process in ORR from O 2 to OH−. In-situ Fourier transform infrared spectroscopy revealed that Pd 4 Au 3 MAs/C enabled the cleavage of the C–C bonds, thus accomplishing the C1-complete oxidation of 10-electron ethylene glycol and 12-electron ethanol. This study provides an efficient strategy to fabricate binary non-Pt alloy aerogels as high-performance multifunctional electrocatalysts for ORR, EGOR, and EOR. [Display omitted] • 3D PdAu aerogels were constructed using an in-situ seed-mediated strategy. • ORR mass activity of Pd 4 Au 3 MAs/C was 11.6 and 17.4 times that of Pt/C and Pd/C. • Pd 4 Au 3 MAs/C possessed superior C2 alcohol oxidation properties. • Pd 4 Au 3 MAs/C achieved 4-electron ORR and complete electrooxidation of C2 alcohols. [ABSTRACT FROM AUTHOR]

Hydrogen transfer leaks are one of the most important life-limiting faults in polymer electrolyte membrane fuel cells (PEMFCs). Hydrogen transfer leaks result in a reduction in the amount of oxygen available in the cathode (air) channel, with large leaks resulting in oxygen starvation and hydrogen emission. This paper aims to develop an adaptive extended Kalman filter (EKF) to estimate the unknown oxygen concentration, which is then used to infer hydrogen leaks. To this end, the paper first develops the lumped model of the fuel cell from a pseudo-2D model of a fuel cell. Next, a (non-adaptive) EKF is developed to estimate the fuel cell states under both normal and oxygen-starved conditions. The adaptive EKF is then implemented by adding the unknown hydrogen leak to the list of estimated states. Finally, the paper demonstrates the efficacy of the proposed adaptive EKF by using it to accurately estimate unknown hydrogen leaks in a high-fidelity virtual fuel cell under excessively noisy conditions. • Adaptive extended Kalman filter under normal and starved conditions. • Detects leaks under the presence of excessive noise. • Uses transient model of starved fuel-cell capturing voltage. • Based on previously validated pseudo-2D model. • Transient response agrees with simulated experiments. [ABSTRACT FROM AUTHOR]

Direct Methanol fuel cells (DMFC) have been limited in their utilization due to their slow cathodic oxygen reduction reaction (ORR) kinetics and the expensive cost of commercial Pt/C catalysts. It is critical to design an oxygen reduction process with high-efficiency catalysts. An approach for modulating the ratio of cellulose, hemicellulose, and lignin in the wheat stalk (WS)/wheat stalk binder (WS binder) precursor materials is proposed in this work. WS binder from alkalization and hydrothermal treatment was added to the WS to change the structure and shape of WS-based carbon materials by varying the ratios, which increased the ORR catalytic activity. The half-wave potential (E 1/2) of the produced carbon material (15 wt% N/C (WS)) is 0.76 V, which was enhanced by 80 mV by adjusting the ratio of the WS/WS binder compared to 0 wt% N/C(WS). The E 1/2 of 15 wt% Fe–N/C (WS) (0.85 V) was greater than that of commercial Pt/C (0.84 V). Besides, its catalytic oxygen reduction process was close to the 4-electron transfer pathway and had good methanol tolerance. The power density obtained with a cathode catalyst of 15 wt% Fe–N/C (WS) for DMFC was 1.39 mW cm−2 at 30 °C and 3.33 mW cm−2 at 60 °C. At different temperatures, the power densities were 1.59 and 1.54 times greater than those of commercial Pt/C catalysts, respectively. [Display omitted] • Binders were added to wheat stalk carbon substrates to change their morphology and structure. • Introduction of Hemin-prepared iron single-atom catalysts with excellent ORR performance. • In DMFC, 15 wt% Fe–N/C(WS) demonstrated a good power density that was better than commercial Pt/C. [ABSTRACT FROM AUTHOR]

The electrocatalytic hydrogen production and supercapacitor technologies have positive impacts on the environment, promoting the production and utilization of clean and renewable energy sources, thus facilitating the reduction of greenhouse gas emissions. Among them, cobalt oxide (Co 3 O 4) has emerged as an ideal choice for electrode materials in these technologies due to its low toxicity, affordability, and significant theoretical capacity. Nevertheless, practical applications are restricted by its low conductivity and sluggish reaction kinetics. Addressing these challenges, this study introduces a pioneering approach: the synthesis of oxygen vacancy-modified Co 3 O 4 /Co/NC small-sized nanoflower composite, which combines the advantages of abundant oxygen vacancies, small size effects, and nitrogen-doped porous carbon. The optimized Co 3 O 4 /Co/NC small-sized nanoflower exhibits high porosity and excellent conductivity, providing numerous active sites and effectively enhancing the ion and electron transport rates. As a consequence, optimized Co 3 O 4 /Co/NC shows a low Tafel slope and overpotential, highlighting its potential for catalytic application. Moreover, as an electrode for supercapacitors, optimized Co 3 O 4 /Co/NC demonstrates excellent long-term stability, maintaining 94.7% of its capacitance even after 5000 charge-discharge cycles. Additionally, it showed a significant specific capacity of 251.4 mAh g−1 when tested at 1 A g−1. In addition to addressing the pressing challenges associated with traditional Co 3 O 4 electrodes, this work opens up exciting avenues for designing and fabricating transition metal oxide-based materials with unprecedented electrochemical performance. This research addresses performance issues with cobalt oxide as an electrode material for capacitors and green hydrogen generation. Innovative methods involving nitrogen doping and the introduction of oxygen vacancies were employed to produce Co 3 O 4 /Co/NC-2 nanosheets with high porosity and a large surface area. These enhancements facilitate faster electrolyte ion diffusion, provide more active sites, and improve electrical conductivity. Nitrogen doping enhances charge transfer rates, while oxygen vacancies offer additional catalytic sites. [Display omitted] • Nitrogen doping and oxygen vacancies enhance the conductivity and reaction rate of cobalt oxide. • Nanoflowers prepared using freeze-drying technology exhibit high porosity, facilitating the diffusion of electrolytes. • This material can be applied in the fields of green catalysis and energy storage. [ABSTRACT FROM AUTHOR]

Herein, a hybrid support of Nb-doped TiO 2 and carbon nanotubes (Nb x TO@CNT, x = Nb wt%) was successfully prepared by a facile hydrothermal method. Controlling the annealing temperature to form either anatase (ANb x TO@CNT) or rutile (RNb x TO@CNT) changed the effect of the Nb dopant in the TiO 2 structure. The Pt/RNb 10 TO@CNT electrocatalyst exhibits excellent oxygen reduction reaction activity and durability (E onset : 0.945 V vs. RHE; E 1/2 : 0.888 V vs. RHE; j L : −6.260 mA cm−2). Theoretical calculations predicted that the synergetic effect of Pt/RNb 10 TO@CNT improves the electrochemical performance. The strong metal-support interaction (SMSI) effect and the formation of oxygen vacancies due to the increased amount of Ti3+ was observed. Band-gap reorganization by the distortion of electronic structures was further confirmed by UV–visible spectrometry. Single-stack polymer electrolyte membrane fuel cell measurements showed the highly improved current density of Pt/RNb 10 TO@CNT (1.913 A cm−2 at 0.6 V) and low current degradation (6.3%) under identical conditions. We report a Nb-doped rutile TiO 2 @CNT hybrid catalyst support prepared by a facile method, namely RNb 10 TO@CNT, which exhibits enhanced activity and ultra-durability of Pt towards ORR by improved SMSI effect caused by Nb doping. [Display omitted] • Nb-doped rutile TiO 2 @CNT hybrid support was designed by a facile synthesis process. • Pt/Nb-doped rutile TiO 2 @CNT ORR catalyst showed reasonable activity and durability. • Nb doping not only controlled electronic structures but also enhanced SMSI effect. • Significantly improved sustainability was exhibited in a single-stack PEMFC cell. [ABSTRACT FROM AUTHOR]

Introducing the second metal is an effective strategy to ameliorate oxygen reduction reaction (ORR) performance of cobalt and nitrogen doped carbon materials (Co-NC). In this study, Sn modulated Co-NC catalysts with enriched active sites (CoSn-NC) were synthesized by using formamide as ligand. Co and Sn bimetals coexist on nitrogen-doped carbon carriers and coordinated with nitrogen to form M − N active centers. Compared with Co-NC, CoSn -NC exhibited outstanding catalytic activity in terms of early initial potential of 1.04 V and positive half-wave potential of 0.89 V. Electrochemical testing and XPS characterization proved that the addition of Sn enriched the active site of Co-NC. More importantly, the electronic structure of Co–N is adjusted to perfect adsorption energy of the intermediate. The study puts forward a new idea and direction for optimizing single metal Co-NC catalyst. Synopsis: This paper is committed to developing Cobalt-based bimetallic materials with enrich active sites to replace scarce Pt/C for ORR. [Display omitted] • Co and Sn bimetals coexist on nitrogen-doped carbon carriers. • Sn Modulated Co-NC catalysts with enriched active sites. • The M − N structure is the main catalytic site by SCN− toxicity experiments. • CoSn-NC shows enhanced ORR catalytic activity, stability and methanol resistance. [ABSTRACT FROM AUTHOR]

Cost-effective, earth-abundant and high electroactive bi-functional electrocatalyst for ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) is desirable for developing sustainable energy systems such as fuel cells, electrolyzers and metal-air batteries. In this work, Ag nanoparticles were first deposited on h-BN sheets via a simple complexation-reduction method, by using carbon nanotube as the conductive material. The structure, morphology and composition of obtained Ag-BN/C catalyst were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy), EDX (energy-dispersive X-ray), Raman, TEM (transmission electron microscopy) and XPS (X-ray photoelectron spectroscopy). These tests confirmed the presence of Ag on the h-BN support and tightly binding together by carbon nanotubes. Ag-BN/C shows improved ORR electrocatalytic activity which is comparable to that of Pt/C catalyst. The as-prepared catalyst also exhibits excellent OER catalytic activity. The long-time running and the tolerance to methanol studies show that the Ag-BN/C catalyst possesses high stability properties in alkaline medium. This investigation may provide technical and theoretical validation for application in fuel cells. [Display omitted] • Ag-BN/C hybrid was synthesized by a complexation-reduction method. • Ag-BN/C possesses high ORR and OER catalytic activity and stability. • Ag-BN/C exhibits excellent tolerance towards methanol. • Synergistic effect is considered as the important factor for catalytic activity. [ABSTRACT FROM AUTHOR]

In this work, we used density functional theory and machine learning (DFT-ML) to predict and screen the first coordination environment (FCE) and second coordination environment (SCE) of A-doped (A = C, N, O, P, and S) coordination environments of FeMA 4 N 2 (M = Fe, Co, Ni, Cu and Zn) and validated it to improve the oxygen reduction reaction (ORR) catalytic activity of FeMA 4 N 2. To expedite the FCE screening, we constructed the Enhanced learning loop framework (EHLN) and ORR descriptors based on convolutional neural networks and transfer learning. EHLN has high accuracy (RMSE is 0.167 V), and high characterization factor R 2 of 86%. Therefore, SCE modification of the optimal overpotential structure (FeFeONCN) of FCE was found to reduce the overpotential to 0.26 V after doping with N and S at sites 4 and 6′. This study brings more possibilities for ORR catalytic activity by tailoring the FCE/SCE of the FeMA 4 N 2 structure. [Display omitted] • The Enhanced learning loop framework constructed for screening catalysts. • A FeM A 4 1 NS structure of multiple nonmetal-doped coordination environments was constructed. • First and second coordination environment doping laws explored. [ABSTRACT FROM AUTHOR]

This study introduces a novel combination of sulfur-doped reduced graphene oxide (S-rGO), zinc ferrite (ZnFe 2 O 4) and nickel cobalt layered double hydroxide (NiCoLDH) as an efficient and low-cost electrocatalyst for oxygen reduction reaction (ORR) for the first time. The hydrothermal method is used to synthesize all samples including graphene oxide (GO), S-rGO, NiCoLDH, ZnFe 2 O 4 and S-rGO/ZnFe 2 O 4 /NiCoLDH hybrids. X-ray diffraction (XRD) analysis, field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), energy dispersive x-ray analysis (EDX), electrochemical surface area (ECSA), and fourier transform infrared spectroscopy (FTIR) analysis are used to determine the structure of synthesized electrocatalysts, physical properties, and morphology. The electrochemical measurements are carried out using cyclic voltammetry (CV), linear scanning voltammetry (LSV), chronoamperometry (ChA), and electrochemical impedance spectroscopy (EIS). The results for all samples are compared with the Pt/C commercial catalyst. According to the electrochemical results, the S-rGO/ZnFe 2 O 4 /NiCoLDH electrocatalyst has the best electrochemical performance. Moreover, the nanocomposite exhibited better electrocatalysis, a high diffusion limiting current density of −5.4 mA cm−2 and an onset potential of 0.03 V. Based on the results of this study, the LDH enhances electrical conductivity, electrocatalytic activity, active surface area, and stability of the catalyst for ORR after combining with carbon bases and ferrite. [Display omitted] • An electrochemical method was utilized for NiCo-LDH on S-rGO/ZnFe 2 O 4. • S doped reduced graphene oxide was used in a composite for improving its ORR activity. • NiCo-LDH was used as electrocatalyst for ORR. • S-rGO/ZnFe 2 O 4 /NiCo-LDH hybrid showed better ORR activity. [ABSTRACT FROM AUTHOR]

In this study, Fe-based metal organic frameworks (MIL-100(Fe)) loaded with CoS 2 /TiO 2 on layered double hydroxide (LDH) was successfully prepared by hydrothermal and solution casting methods, which was utilized as novel catalyst for bioelectricity generation and cathodic oxygen reduction reaction (ORR) in microbial fuel cell (MFC). Electrochemical tests showed good oxygen reduction activity. The maximum power density of CoS 2 /TiO 2 /MIL-100(Fe)@NiFe-LDH-MFC was 75.272 mW/m2, which was 1.17 times higher than that of CoS 2 /TiO 2 @NiFe-LDH-MFC (64.082 mW/m2) and 1.2 times higher than that of CoS 2 /TiO 2 @MIL-100(Fe)-MFC (62.658 mW/m2), 2.03 times that of CoS 2 /TiO 2 -MFC (36.992 mW/m2), and 3 times that of TiO 2 -MFC (25.088 mW/m2). CoS 2 /TiO 2 /MIL-100(Fe)@NiFe-LDH-MFC possessed a maximum output voltage of 194 mV and a stabilization time of 220 h CoS 2 /TiO 2 /MIL-100(Fe)@NiFe-LDH possessed potential applications as a kind of potential cathode catalyst to further improve the electrochemical performance of fuel cells. [Display omitted] • CoS 2 /TiO 2 /MIL-100(Fe)@NiFe-LDH was prepared by simple hydrothermal method. • Maximum power density of CoS 2 /TiO 2 /MIL-100(Fe)@NiFe-LDH-MFC was 75.272 mW/m2. • Modification of TiO 2 with CoS2 improved conductivity and MIL-100(Fe) enhanced stability. [ABSTRACT FROM AUTHOR]

We develop a method for bifunctional regulation on the surface micro-morphology and nitrogen-doping configuration of graphene-based nanosheets by annealing chitin and graphene oxide. Systematic studies reveal that annealing temperature is a key to determine micro-morphology and type of nitrogen-doping of the graphene matrix, and 2D multi-wrinkled graphene (CS-rGO-600) with enriched active nitrogen species and moderate defects can be obtained successfully under an optimized annealing temperature. When used as a "green" electrocatalyst for oxygen reduction reaction (ORR), CS-rGO-600 exhibits superior performance, in terms of more outstanding electrode activity and durability, higher output power density in fuel cell system compared to that of Pt/C. These could be attributed to the fact that appropriate annealing treatment is not only conducive to exogenous nitrogen enrichment and oriented conversion but also beneficial to micro-structure construction. The synergistic effects between multi-wrinkled 2D structure and active sites endow CS-rGO-600 with superior ORR performance in the fuel cell. • CS-rGO-X was prepared via pyrolysis of biomass waste and GO. • Appropriate pyrolysis is conducive to N enrichment and structure construction. • Synergism between structure and active sites endow CS-rGO-600 with superior activity. • CS-rGO-600 with highest E onset (0.059 V) and P max (0.665 mWcm−2). [ABSTRACT FROM AUTHOR]

Transition metal and nitrogen doped carbons (M-N-C) catalysts present significant potential as substitutes for platinum-carbon (Pt/C) in catalyzing oxygen reduction reaction (ORR). Hence, we employ an epitaxial growth strategy to prepare Zn/Co-ZIF@ZIF-8 crystals with core-shell structure. Subsequent pyrolysis and acid etching produce highly porous cobalt-doped nitrogen materials for ORR investigation. The resulting Co-NC@NC catalyst demonstrates a graded porous structure alongside remarkable conductivity, possessing a specific surface area measuring 623 m2 g−1. It showcases heightened ORR activity with a half-wave potential (E 1/2) of 0.886 V, superior kinetic performance (illustrated by an extremely low Tafel slope measuring 45.98 mV/dec), and strengthened stability (with mere 25 mV day after 40,000 cycles) when contrast with Pt/C catalysts in 0.1 M KOH. Additionally, it exhibits notable activity and stability in acidic environments. These remarkable attributes are attributable to the graded structure, which facilitates rapid mass transfer, a high electrochemically active area that exposes highly dispersed active sites, and a conductive carbon skeleton network that promotes electron transfer. • Ion exchange-epitaxial strategy synthesizes core-shell cobalt nanoparticles. • Graded porous structure enhances active sites and accelerates mass transfer. • Catalyst shows excellent ORR stability and activity in all pH environments. • Catalyst exhibits 25 mV E 1/2 decay after 40000 cycles of ADT. [ABSTRACT FROM AUTHOR]

From micro to macro level, the performance of zinc-air flow battery (ZAFB) hinges on two crucial factors: the effective oxygen reduction reaction (ORR) electrocatalysts, and the durable triple-phase electrodes. However, sluggish kinetic process always occurs due to insufficient active sites and hysteretic mass transfer. In this work, a well-confined iron phthalocyanine (FePc) structure onto carbonized metal-organic framework (C-MOF5) electrocatalyst is constructed through a pyrolysis-free strategy. The macrocyclic skeleton of MOF-5 has been confirmed to offer a stronger and more abundant environment for hosting FePc molecules. Attributing to the hierarchical pore engineering of MOF-5, the FePc@C-MOF5 electrocatalyst reveals a high content of Fe (5.68 wt%) with multiple exposed active sites. Notably, the FePc@C-MOF5 exhibits a remarkably high half-wave potential of 0.915 V for ORR in 0.1 M KOH, surpassing that of commercial Pt/C by nearly 60 mV. From a higher-level device perspective, the highest oxygen diffusion velocity and local current density of the FePc@C-MOF5 electrode is verified by computational fluid dynamics (CFD) simulations. As a result, the as-assembled ZAFB demonstrates long-term stability with 200 h' cycling. This work not only presents the hierarchical pore tailoring strategy for designing ORR electrocatalysts but also offers a deeper understanding of the essence of interfacial mass transfer. A novel FePc@C-MOF5 electrocatalyst for zinc-air flow batteries was proposed, enhancing ORR performance and stability while advancing understanding of mass transfer dynamics. [Display omitted] • A well-confined MOF-5-derived ORR catalyst was prepared with a high loading of Fe. • The unique pore structure accelerates both oxygen diffusion and charge transfer. • The FePc@C-MOF5 reveals good activity at both microscale for three-electrode characterization and macroscale for ZAFB test. • A numerical three-dimensional model combining transfer theory with reaction kinetics for ZAFB is established. [ABSTRACT FROM AUTHOR]

Herein, four different metal-free nitrogen containing Covalent Triazine Frameworks (CTFs) based on their applied monomers (DCP, DCBP, m DCB and p DCB) are synthesized via a classical ionothermal synthesis route (ZnCl 2 , 400/600 °C). These materials are fully characterized and their electrochemical activities for ORR are tested and compared to each other including Carbon Super P and Pt black as standards in 0.1 M KOH. While DCP provides similar catalytic activity to Carbon Super P showing mostly a 2eˉ process (n=2.95) with high H 2 O 2 formation of 52.6 %, the other three CTFs (DCBP, m DCB and p DCB) possess higher ORR activities, surprisingly even much higher limiting current densities than Pt black, proving that O 2 is mainly reduced via direct 4eˉ pathway since n values are in the range of 3.52 to 3.62 and the detected H 2 O 2 values are in the range of 19–23.9 %. Among the studied CTFs, m DCB reaches a limiting current density of −5.61 mA cm-2 (1.21 mA cm-2 larger than that for Pt black, −4.40 mA cm-2) with 0.11 V larger onset potential compared to Pt black. The significant electrochemical performances of the CTF materials in ORR via a 4eˉ process are correlated to the high specific surface areas (up to 2500 m2 g-1), large pore volumes (up to 2.05 cm3 g-1) and the largest total N-graphitic/quaternary contents as well as micro-mesoporous structure properties. [Display omitted] • Four N-containing Covalent Triazine Frameworks (CTF) were synthesized via a classical ionothermal route. • Three CTFs provide higher ORR activities, with much larger limiting current densities than Pt black. • O 2 is mostly reduced through a direct 4eˉ process rather than 2eˉ process at three CTFs. • The N-graphitic/quaternary sites are the active sites for oxygen reduction reaction (ORR). [ABSTRACT FROM AUTHOR]

Platinum catalysts are widely used in electrocatalytic water splitting for the hydrogen evolution reaction and in hydrogen fuel cells for the oxygen reduction. Nonetheless, the practical use of the noble metal platinum in commercial applications faces significant challenges due to its exorbitant cost and the intricate nature of its synthetic methods. In this work, nitrogen-doped carbon layers covering platinum particles (Pt@NCL) are uniformly distributed on carbon nanofiber (CNF) substrates to synthesize heterojunction catalysts (Pt@NCL-CNF). Multiple characterization methods reveal that the nanoscale ultra-thin carbon layer successfully activates platinum nanoparticles and creates a tremendous accumulation of valence electrons at the interface of the heterojunction catalysts. Furthermore, the greater the number of defects produced in the ultra-thin carbon layer of Pt@NCL-CNF during the reaction, the more active sites are exposed. Therefore, Pt@NCL- CNF exhibits much better hydrogen evolution reaction and oxygen reduction reaction performance in pH-universal electrolytes than the commercial carbon-supported platinum (Pt/C) catalyst. This study elucidates the reaction mechanism, highlighting the crucial role of the ultra-thin carbon layer within the catalyst, and also confirms the catalyst performance in device applications. The proposed method can provide a simple and feasible mass-produced approach for the preparation and application of high performance low platinum catalyst. A heterogeneous bifunctional catalyst (Pt@NCL-CNF) is engineered with a core-shell architecture, incorporating a Platinum core ensconced within an ultra-thin carbon shell, all mounted on supportive carbon nanofibers. [Display omitted] • Pt@NCL-CNF catalysts have better PH-universal HER/ORR performance than commercial Pt/C. • Illustrate the reaction mechanism for Pt@NCL-CNF heterojunction. • Reveal the interface electronic interaction and ultra-thin carbon surface formative defects. • Confirm the feasible route of ultra-thin carbon layer covering Pt-based catalysts. • Validation of the application potential of Pt@NCL-CNF in devices. [ABSTRACT FROM AUTHOR]

One of the biggest challenges to the sustainable manufacture of liquid ammonia and the prevention of worldwide water contamination is the development of effective electrocatalysts for the electrochemical reduction of nitrate (NO 3 −) to NH 3 with high stability. Herein, a highly active and serviceable electrocatalyst is synthesized by pyrolysis, composed of nanostructure nickel phosphide (Ni 2 P) embedded in nitrogen phosphide doped carbon (NPC) followed by deposition on carbon paper (CP) to improve the electrocatalytic nitrate reduction. Various characterization techniques investigate the crystallinity, morphology, and chemical components of the Ni 2 P-NPC/CP nanoparticles. The results support the formation of nanostructure Ni 2 P and strong synergistic interactions between Ni 2 P and NPC, which resulted in substantial active sites and high electrical conductivity. Excellent performance of Ni 2 P-NPC/CP nanoparticles is achieved for electrocatalytic NO 3 − reduction with an NH 4 + yield rate of 2.468 mg h−1 mg cat. −1 and Faradaic efficiency (FE) of 84.6% at −1.2 V vs. RHE. Additionally, Ni 2 P-NPC/CP nanoparticles exhibit exceptional robustness and endurance. Studies using isotope labeling have been carried out, and the results show that nitrate reduction produces ammonia. Ni 2 P-based electrocatalysts can effectively treat nitrate wastewater to recover ammonia and facilitate its use in diverse industrial applications. • Ni 2 P-NPC/CP offers a highly active and durable electrocatalyst for the conversion of nitrate to ammonia. • Ni 2 P-NPC/CP achieved NH 4 + yield rate of 2.468 mmol h−1 mgcat−1 and Faradaic efficiency of 84.6% at −1.2 V. • The unique Ni 2 P-NPC/CP ensures robustness and practical options for continuous nitrate reduction processes. • Ni 2 P-NPC/CP offers a carbon-free energy solution through the selective conversion of nitrate to NH 3. [ABSTRACT FROM AUTHOR]

Low cathodic oxygen reduction reaction (ORR) efficiency is one of the important factors limiting the hydrogen fuel cells. Platinum can effectively reduce the ORR activation energy and improve the reaction rate; However, platinum's low reserves, versatility, and high price still limit its use in commercial, large-scale applications. It is very important to reduce the amount of Pt and improve the utilization rate and the stability of Pt-based catalyst. Here, an ultra-low Pt content catalyst Pt&Fe 2 O 3 /PM has been synthesized. The Pt content of the catalyst is only 4 wt%, and its nanoparticles are about 3 nm. Pt&Fe 2 O 3 /PM exhibit excellent ORR catalytic performance and longevity in acidic electrolyte. The ORR mechanism on Pt&Fe 2 O 3 /PM involves a direct four-electron path. The mass activity and specific activity of Pt&Fe 2 O 3 /PM is 4.8 and 10.3 times than that of commercial Pt/C, respectively. Furthermore, the catalyst's synthesis method is straightforward and amenable to scaling up, offering significant guidance for the creation of low-Pt catalysts. [Display omitted] • High dispersion low-Pt catalyst Pt&Fe 2 O 3 /PM was prepared by heat treatment. • The particle size of the Pt&Fe 2 O 3 /PM is ca. 3 nm, and the Pt content is ca. 4 wt%. • Pt&Fe 2 O 3 /PM has higher ORR activity and durability than commercial Pt/C. [ABSTRACT FROM AUTHOR]

Due to structural complexity and limited understanding, precise chemical modification in atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts requires theoretical calculations to optimize electronic, geometric, and catalytic performance and experimental implementation of learned lessons to improve their catalytic performance towards oxygen reduction reaction (ORR). Herein, we conducted a density functional theory (DFT) investigation to understand the effect of the replacement of O-atoms in Fe–O 4 –C by N-atoms in the first coordination shell of Fe-site (constructing five models: Fe–O 4 –C, Fe–O 3 N–C, Fe–N 2 O 2 –C, Fe–ON 3 –C and Fe–N 4 –C) towards ORR. The geometric and electronic calculations of these models suggested that replacing all the O-atoms with N-atoms around the Fe-site would make it more conducive to the adsorption of ORR intermediates. Moreover, the Gibbs free energy calculations demonstrated that the Fe-site becomes the active centre for 2e− ORR, leading to the dominant generation of H 2 O 2 when Fe is coordinated with four O-atoms (Fe–O 4 –C). Whereas in compounds like Fe–N 2 O 2 –C, Fe–O 3 N–C, and Fe–N 4 –C, where the Fe-site displays 4e− ORR, form water is a preferred product if the O-atoms are replaced by N-atoms, as in Fe–N 2 O 2 –C, Fe–O 3 N–C, and Fe–N 4 –C. This study would provide a fundamental understanding of how atomically dispersed M-N-C catalysts' electrocatalytic activity is affected by changes in the coordination environment of metal sites. [Display omitted] • A theoretical approach was used to construct the models of Fe-NxOy-C-based electrocatalysts. • The models Fe–O 4 –C, Fe–NO 3 –C, M–N 2 O 2 –C, M–N 3 O–C, and M-N4-C, were completely investigated via DFT approaches. • The O 2 adsorption at the Fe–N 4 –C catalyst was the determining step during the associative pathway. • The M-N 4 -C catalytic moel displayed 4e- ORR, while the M-O 4 -C catalyst showed 2e- ORR. [ABSTRACT FROM AUTHOR]

Facile synthesis of highly-dispersed Pt-based electrocatalysts on porous carbon supports with strong durability is extremely desirable for oxygen reduction reaction but remains challenging. The influence of pores in carbon supports on the stability and activity of catalysts is ambiguous and needs to be elucidated. Targeting this aim, herein, we prepared a series of carbon nanofibers with tunable pore diameter and specific surface area using the resorcinol-formaldehyde (RF) resins as a model system. Homogeneous composite precursors composed of RF resins and silica colloids were synthesized by the surfactant-assisted simultaneous polycondensation of RF resins and tetraethylorthosilicate (TEOS). The diameter of the pores induced by removal of silica could be controllable tailored through thermal treatment of the composite under various target temperatures. Pt 3 Co alloy nanoparticles loaded on the as-synthesized porous carbon nanofibers were prepared by an optimized wet-impregnation method. The experimental results indicated that the carbon nanofibers with pore size distribution focused on ∼1.27 nm and ∼2.34 nm provided the best stability without limiting current density decay, and negative shift of half-wave potential (E 1/2) and mass activity (MA) loss of Pt after 20000 potential cycles are relatively mild. Conversely, negative shift of 21 mV, 15 mV and 22 mV in E 1/2 and mass activity loss of 51.8%, 30.2% and 33.0% were observed for the Pt 3 Co nanoparticles supported on MC-60, MC-100 and MC-140 matrices which have pore size distribution focused on ∼2.73 nm, ∼2.73 nm as well as ∼4.66 nm, and ∼4.66 nm, respectively. This work demonstrates the importance of micropores and small mesopores for activity and long-term stability enhancement of carbon supported Pt-based electrocatalysts. Porous carbon nanofibers with tunable pore size distribution were synthesized by combining the surfactant-assisted simultaneous polycondensation of resorcinol-formaldehyde resins and TEOS with elaborate designed thermal treatment. Pt 3 Co nanoparticles loaded on the carbon with pore size distribution focuses on ∼1.27 nm and ∼2.34 nm provided the highest activity and best stability with no performance decay for ORR after 20000 potential cycles. [Display omitted] • Composite fibers of RF resins and Silica were synthesized by the developed surfactant-assisted polycondensation strategy. • Diameters of the mesopores in the synthesized carbon fibers could be controllable tuned. • Mesopores with diameter of ∼2.34 nm are efficient for boosting the stability of the carbon supported Pt 3 Co for the ORR. [ABSTRACT FROM AUTHOR]

The utilization of atom-dispersed Cu-N x site catalysts holds significant promise as a replacement for commercial Pt/C catalyst in the context of oxygen reduction catalysts. However, practical application of these catalysts has been hindered by their insufficient catalytic activity. It is imperative to enhance the oxygen reduction reaction (ORR) catalytic activity of the Cu-N x catalysts by manipulating electronic structure of the Cu-N x site. This study presents the synthesis of a composite catalyst, formed by coupling Cu nanoclusters and Cu-N x catalysts through pyrolysis of protein-Cu2+ gel followed by acid-leaching treatment. The resultant composite catalyst demonstrates superior ORR activity as compared to isolated Cu-N x catalysts under alkaline conditions. Through density functional theory (DFT) calculations, the synergistic mechanism of the coupled Cu nanoclusters and Cu-N x for ORR catalytic activity is elucidated. The proximity of the Cu nanoclusters (Cu 4) to the central Cu atom of Cu-N x (CuN 4) in the composite catalyst causes a shift in the d-band center of the active Cu site towards the Fermi level. This shift strengthens the binding energy of O 2 adsorption, reduces ORR overpotential, and combines with favorable electron transfer from Cu nanoclusters to Cu-N x sites, thereby enhancing ORR activity. These findings contribute novel insights into the enhancement of ORR catalysis performance through the manipulation of electron structures via nano-sized metal clusters. [Display omitted] • Cu-N x and Cu nanoclusters were coupled by simple pyrolysis and acid etching. • As-Formed micropore structure stabilizes Cu-N x sites and enhances ORR activity. • DFT calculations revealed the enhanced ORR activity on the coupled catalysts. • The coupled Cu-N x and Cu nanoclusters catalysts showed superior durability. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) has higher energy barrier and slower kinetics, which limits the efficiency of electrocatalytic water splitting. Developing efficient catalysts is of great significance for improving oxygen evolution performance. Therefore, we developed a low-dose ruthenium-doped copper-nickel bimetallic organic framework self-supported electrode (Ru x CuNi-MOF/CF). The prepared Ru 0·004 CuNi-MOF/CF has excellent electrocatalytic activity and stability. At the current density of 10 mA cm−2, the overpotential is only 203 mV in 1 M KOH electrolyte, and it can work continuously and stably for 100 h. The Tafel slope of Ru 0·004 CuNi-MOF/CF is 57.01 mV dec−1. The excellent electrocatalyst performance is attributed to the following three points: (1) The self-supporting material does not need adhesives to avoid the inhibition of the conductive ability of the catalyst. (2) The Cu2+/Ni2+ lattice site is replaced by Ruδ+, and the electron rearrangement improves the conductivity and catalytic activity of the material. (3) The presence of zero-valence ruthenium nanoparticles can further provide more active sites and improve the electrochemical reaction rate. This work provides new insights into fabricating ruthenium-doped bimetallic organic framework self-supported electrode for the study of oxygen evolution performance. • Ingenious use of substrate in situ conversion to provide part of the metal source, reduce the cost of the experiment. • The Ru 0·004 CuNi-MOF/CF exhibits excellent durability after 100 h of continuous operation. • The electronic structure is regulated by Ru0/Ruδ+ to improve the electrochemical performance. [ABSTRACT FROM AUTHOR]

Hydrogen evolution reaction (HER) has gained a great interest in recent years because it provides the cleanest fuel (H 2). One of the most demanding things required for this reaction is an efficient and cost-effective catalyst. Single atom catalysis is one of the most remarkable strategies in this regard. Herein, transition metals adsorbed silicon carbide nanocages (TM@Si 12 C 12 ; TM = Zn, Fe, Co, Cu, Ni) are investigated as single atom catalysts in order to search less expensive electrocatalysts with excellent efficiency for HER. The pure and hydrogen adsorbed TM@Si 12 C 12 show geometric and thermodynamic stability which illustrates their practical utility. Interaction energies obtained range from −0.70 to −5.73 eV, and it is suggested that Cu@Si 12 C 12 may play an excellent role in HER due to its lowest Gibbs free energy of −0.17 eV (near to zero). In this work, we investigated electronic properties through natural bond orbital (NBO) analysis of selected TM@SiC. According to NBO calculations, it is observed that charge is transferred from adsorbed transition metals towards nanocage. After H adsorption, NBO charge is transferred to hydrogen which shows the adsorption properties of H. In case of HOMO-LUMO energy gap, it is observed that transition metal adsorbed complexes have small energy gaps between 2.17 and 2.77 eV but after adsorption of hydrogen, this energy gap increases to lie in the range of to change from 2.93 to 3.12 eV, which also verified the electronic stability of H adsorbed species. The noncovalent interactions are estimated through NCI analysis. The density of states analysis gives insight about the energy states of occupied and unoccupied orbitals of electrons. The highest thermodynamic stability and electronic conductivity of transition metal adsorbed silicon carbide suggested it as an excellent supportive surface for HER. [Display omitted] • Transition metals doped Si 12 C 12 nanoclusters are used as single atom catalyst toward HER. • Thermodynamic and electronic properties of hydrogen adsorbed TM@Si 12 C 12 are investigated via DFT method. • Cu@Si 12 C 12 has excellent HER efficiency due to very low Gibbs free energy (−0.17 eV). [ABSTRACT FROM AUTHOR]

In this paper, a new design principle for bimetallic catalysts is proposed by combining strongly adsorbed atoms (SAA) with weakly adsorbed atoms (WAA) where the SAA and WAA are classified by the free adsorption energy of oxygen-containing intermediates on the metal atom. And the ORR performances of the bimetallic catalysts designed by the method are compared with the common single metal atom catalysts. The method is successfully confirmed as the overpotential of the Mn-based bimetallic catalysts decreases from 0.63 V in G-MnN 4 to as low as 0.33 V, and that of the Fe-based bimetallic catalysts decreases from 0.76 V in G-FeN 4 to 0.23 V. In addition, the correlation between adsorption free energy and adsorption bond length is revealed for the first time, and the optimal adsorption bond length is determined. Finally, the adsorption energy of O 2 is plotted versus the free adsorption energy of three oxygen-containing intermediates for the first time, and a suitable adsorption energy of O 2 is found to be -1.4∼-1.0 eV. These findings provide a new perspective for the design of high-performance bimetallic catalysts. • Catalysts obtained by combining strongly adsorbed atoms with weakly adsorbed atoms show superior performance. • Correlation between adsorption free energy and adsorption bond length is revealed for the first time. • Adsorption energy of O 2 can be used as a descriptor of ORR performance. • ORR performance is related to the energy difference of hybridization between metal atom and adsorbed species. [ABSTRACT FROM AUTHOR]

The research of high-performance catalysts for ORR is always a great challenge in the field of zinc-air batteries (ZABs) applications. Herein, a near-regular dodecahedral ZIF-67-derived nitrogen-doped carbon material (CeCo-N x CC-700) with abundant hollow nanospheres on the surface is successfully constructed by introducing Ce ions to replace part of the Co ions and polymerizing pyrrole on the surface of the polyhedrons. PPy-coating is beneficial to improving the electrochemical stability and increasing the number of Co-N x active sites, especially the pyrrole N and pyridine N sites. Ce-doping adjusts the charge density around the active sites. Meanwhile, the pyrolysis at 700 °C during the preparation process does not cause the structural collapse of CeCo-N x CC. Based on their decent ORR/OER performance, ZABs have been further assembled with CeCo-N x CC-700, which exhibit a high specific capacity of 815.4 mAh·g (Zn)−1 and cycling stability of more than 80 h, indicating a great application potentiality in ZABs manufacturing. [Display omitted] • Designed a novel heterogeneous hollow polyhedron CeCo-N x CC electrocatalyst. • Withstood high temperature pyrolysis without the hierarchical structure collapsing. • Increased the number of active sites and improved the electrochemical stability by PPy-coating. • Adjusted the charge density around the active sites by Ce-doping. • Assembled rechargeable ZABs with CeCo-N x CC with high performance. [ABSTRACT FROM AUTHOR]

A Platinum-based graphene nanosheet electrocatalyst (Pt/GNS) was modified by changing its surface chemical composition (or functionalization), using citric acid via solid state method. The physical characterizations were orderly carried out by Raman spectroscopy, Fourier transform infrared spectroscopy, thermo-gravimetric analysis,X-ray powder diffraction, field emission scanning electron microscope, and transmission electron microscope. Electrocatalytic activity concerningto oxygen reduction reaction (ORR) of the synthesized catalyst was measured using a rotating disk electrode coupled with potentiostat/galvanostatinalkaline (0.1 M KOH) solution, and the performance was compared to conventional Pt/C catalyst. The developed electrocatalyst holds superior electrocatalytic properties compared to the unfunctionalized catalyst and Pt/C. Functionalized Pt/GNS exhibited better oxygen reduction activity of (0.86 V half-wave potential) and demonstrated 3.9 e− transfer against a single oxygen molecule. After 10,000 potential cycles of stability performance, the developed electrocatalyst showed remarkable durability. • Pt anchored graphene nanosheets were employed as electrocatalyst for ORR. • Pt/GNS was functionalized by using citric acid via the solid state method. • Pt/GNS showed improved electrocatalytic activity for ORR. • Pt/GNS showed the long-term stability towards ORR activity. [ABSTRACT FROM AUTHOR]

The development of cost-effective and highly active catalysts for the oxygen reduction reaction (ORR) is crucial for the successful commercialization of Zn-air batteries. Single-atom catalysts are considered to be the most promising alternatives to Pt-based catalysts on account of their high atomic utilization and adjustable coordination environment, but their activity and durability are not ideal. Herein, a porous nitrogen-doped graphene with atomically-dispersed Fe sites (Fe SAs/NG) is developed by utilizing g-C 3 N 4 as the nitrogen source. The Fe SAs/NG exhibits superior ORR property in alkaline electrolyte with a high half-wave potential (E 1/2 = 0.883 V vs. RHE) and remarkable stability, mainly due to atomically-dispersed Fe sites, abundant N species, and porous structure. Moreover, the Fe SAs/NG-based Zn-air battery achieves the maximum discharge power density of 272.6 mW cm−2, surpassing that of benchmark 20% Pt/C catalyst (238 mW cm−2). This study offers a valuable reference for the rational design and synthesis of high efficiency single atom catalysts specifically tailored for Zn-air batteries. • A porous nitrogen-doped graphene with atomically-dispersed Fe sites (Fe SAs/NG) is successfully prepared. • The porous two-dimensional nanosheet structure possesses more accessible active sites. • The catalyst exhibits superior catalytic activity and stability toward ORR in alkaline electrolyte. • Fe SAs/NG-based Zn-air battery demonstrates a maximum power density of 272.6 mW cm−2. [ABSTRACT FROM AUTHOR]

As the kinetic processes of oxygen reduction (ORR) and oxygen evolution reaction (OER) in metal-air batteries are slow, developing bifunctional catalysts with high performances is an essential requirement for boosting metal-air battery application. FeCo alloy is considered an excellent bifunctional active material, its weak corrosion resistance precludes its practical use in bifunctional catalysts. In this work, through dipping and annealing operations, FeCo alloy nanoparticles are doped on the porous carbon spheres (FeCo/PCNs). Strong FeCo nanoparticle-nitrogen-doped porous carbon sphere interaction results in a noticeable improvement in electrocatalytic activity and stability. FeCo/PCNs catalyst shows impressive bifunctional electrocatalytic activity, half-wave potential (E 1/2) of 0.905 V for ORR, and overpotential of 344 mV at a current density of 10 mA cm−2 (E j = 10) for OER, which are better than commercial Pt/C (E 1/2 = 0.865 V) and RuO 2 (E j = 10 = 351 mV) catalysts. Furthermore, the Zinc-air battery (ZABs) prepared by FeCo/PCNs catalyst (ZAB-FeCo/PCNs), exhibits high open circuit voltage (1.53 V), high power density (135 mW cm−2), and good long-term cycle stability, which further proves that FeCo/PCNs has excellent ORR/OER bifunctional activity. Therefore, the unique FeCo/PCNs catalyst provides a new perspective for the construction of ZABs bifunctional catalysts. [Display omitted] • FeCo/PCNs catalyst is prepared via impregnation and pyrolysis processes. • FeCo alloy in FeCo/PCNs catalyst promotes the graphitization the PCNs skeleton. • FeCo alloy and Fe/Co-N x active sites endow catalyst with high OER/ORR activity. • ZABs with FeCo/PCNs catalyst show better property than Pt/C + RuO 2. [ABSTRACT FROM AUTHOR]

Although great progress has been made in the study of the performance of NiFe-based electrocatalysts, the specific role of Fe is still under debate, largely due to the lack of desirable platforms. Metal-organic frameworks (MOFs) with uniform pore size, large specific surface area and uniform distribution of active sites are ideal platforms. Therefore, we synthesized a series of NiM-MOF (M = Fe, Co, Mn, Cu, or Zn) nanosheet arrays by solvothermal method with MOF as a platform and systematically investigated their OER properties. XRD and XPS characterizations show that the introduction of Fe into Ni-MOF not only leads to lower crystallinity, but also increases the oxidation state of Fe and modifies the electronic structure of Ni sites. This is further confirmed by DFT calculations, where the d-band center is closer to the Fermi level, enhancing the ability to adsorb/desorb oxygen-containing intermediates and thereby improving the intrinsic activity of NiFe-MOF. By combining material characterizations and DFT calculation, a series of NiM-MOF (M = Fe, Co, Mn, Cu, or Zn) nanosheet arrays have been synthesized as a platform to elucidate and verify the specific roles of Fe in NiFe-MOF towards alkaline OER. [Display omitted] • NiM-MOFs (M = Fe, Co, Mn, Cu, or Zn) nanosheet arrays were synthesized as OER catalysts. • Fe incorporation optimized the crystallinity and electronic structure of the NiFe-MOF. • DFT was used to elucidate and verify the specific role of Fe in NiFe-MOF towards OER. [ABSTRACT FROM AUTHOR]

Platinum group catalysts are still the most effective catalysts for oxygen reduction reaction (ORR) of proton exchange membrane fuel cells. Thus, the high cost and susceptibility to deactivation during working process are becoming more and more prominent with the proceeding of the application. To meet the requirements of enhancing reaction kinetics and decreasing the cost of Pt-based catalysts, we design a N -doped hollow carbon nanorods (HCNR) supported platinum-nickel based catalyst for ORR. Compared with the benchmark commercial Pt/C catalyst, the HCNR supported PtNi catalysts (PtNi/HCNR) show excellent catalytic activity for ORR and long-time running durability. The onset potential (E 0) and half wave potential (E 1/2) of medium platinum content catalyst (PtNi/HCNR-2) catalyzed ORR are 1.02 V and 0.914 V, separately, which surpass than that of the 20 wt% Pt/C catalyst. Furthermore, PtNi/HCNR-2 catalyzed ORR has a lower Tafel slope (92.05 mV dec−1), faster electron transfer rate, lower H 2 O 2 yield rate and better stability. The synergistic effect between N -doped HCNR and PtNi alloy assures the high performance for ORR. HCNR improves the electrical conductivity, while the doped nitrogen provides "coordination nests" for PtNi catalyst, which provide more catalytic active sites for ORR. PtNi/HNCR-based catalysts have great potential to be low-cost, high performance catalysts for ORR. [Display omitted] • N -doped hollow carbon nanorods support for catalysts were synthesized. • HCNR supported PtNi catalysts show 20 mV higher onset potential for ORR than Pt/C. • Doping with nitrogen enhanced the affinity between HCNR and PtNi catalyst. • Hollow structure facilitates the transport of oxygen and electrons for ORR. [ABSTRACT FROM AUTHOR]

It is necessary to seek oxygen reduction reactions (ORRs) electrocatalyst that can replace commercial Pt/C for new energy conversion devices. Herein, we used molten salt-assisted pyrolysis to successfully convert small nitrogen-containing carbon molecules directly into iron-nitrogen codoped carbon nanospheres (Fe–N–Cs) without the need for external templates. Molten salts provide a solvo-like environment for the high-temperature pyrolysis of small carbon molecules and bulk oxides. Small molecules containing nitrogen and carbon are subjected to spatial domain-limiting effect, reducing volatilization in the calcination processes. Besides, the strong polarity provided by molten salts can not only dissolve bulk oxides but also prevent free metal atoms from gathering again to form particles or clusters. The synthesized Fe–N–Cs exhibit excellent ORR activity. The half wave potential (E 1/2 , 0.67 V vs. RHE) in acidic solution is almost equivalent to Pt/C. Furthermore, Fe–N–Cs have the ability to prevent methanol poisoning and its stability is strong. [Display omitted] • Small molecules containing nitrogen were directly converted into carbon nanospheres. • The Fe–N–Cs was prepared by template-free melting salt-assisted pyrolysis. • The molten salts can provide a high polarity environment. • The Fe–N–Cs showed excellent ORR activity in alkaline and acidic solution. [ABSTRACT FROM AUTHOR]

In this paper, we present a method to enhance the stability of Fe–N–C electrocatalysts, known for their significant oxygen reduction reaction (ORR) activity and positioned as promising alternatives to commercial noble metal-based catalysts. Despite the favorable ORR activity, Fe–N–C suffers from inadequate stability in acidic media, primarily attributed the loss of active FeN 4 sites resulted from Fe-demetalation. However, recent investigation reveals that pyridine N exhibits remarkable stability in retaining Fe atoms. To address this, we achieved a high proportion of pyridine N doping in carbon nanofibers through a process involving nano-SiO 2 shell coating and electrospinning. The nano-SiO 2 shell coating method demonstrates efficacy and versatility in transforming pyrrole-type FeN 4 into pyridine-type FeN 4 , irrespective of the origin material being trivalent or divalent Fe, whether organic or inorganic. [Display omitted] • Obtained a high pyridine proportion Fe–N–C electrocatalyst with long-term stability • Developed a method for the transformation from the pyrrole-type FeN 4 to pyridine-type FeN 4. • The method is applicable to both trivalent and bivalent iron, regardless of inorganic or organic. [ABSTRACT FROM AUTHOR]

Accelerating the commercialization of fuel cells requires the development of Pt-based alloy cathode catalysts with high ORR operation, low price, and excellent reliability. However, it is a challenging task to fabricate uniformly dispersed, low-loaded, and small-sized Pt-based alloy catalysts to resolve the contradiction between activity and stability. Here, sub-3 nm N-doped PtNi nanoparticles (NPs) are synthesized as high-performance PEMFC cathode catalysts. PtNi/Ni-NC exhibits excellent electrocatalytic activity (0.51 A mg Pt −1@0.8 V and peak power density of 328 mW cm−2) as well as stability (only 15 mV loss in E 1/2 after 5000 cycles of ADT tests) in oxygen reduction reaction (ORR). The experimental results show that N doping modulates the electronic structure around Pt and optimizes the lattice compressive strain, thus attenuating the adsorption of oxygen intermediates on the surface Pt and enhancing the ORR activity. Meanwhile, the encapsulation of PtNi NPs by the constructed ultrathin Ni–N–C layer accounts for the improved stability. This work offers a novel perspective f for raising the stability and catalytic performance of Pt-based catalysts. • N doping provides optimum compressive strain on the dominating surface of PtNi (111). • Constructed ultrathin Ni–N–C layers can encapsulate small PtNi NPs and strengthen their targeting. • PtNi/Ni-NC with sub-3 nm can be used as an efficient ORR catalyst for MEA. [ABSTRACT FROM AUTHOR]

This work utilized an innovative and economical remediation method to convert inexpensive waste feedstock into extremely useful catalysts. The procedure centered on polyethylene (PE), an easily accessible substance, and effectively transformed it at a mild temperature utilizing a new solvothermal technique, which entailed the reaction of sulfuric acid with PE chains at 120 °C. Throughout this process, the polymer experienced a pivotal cross-linking stage, resulting in its conversion into carbon materials when exposed to temperatures above 500 °C. To improve the catalytic characteristics, platinum (Pt) was effectively integrated into the resultant carbon matrix using the existing impregnation technique. Further, the catalyst's physicochemical properties were thoroughly analyzed utilizing SEM, FTIR, and XRD techniques. After that, the catalyst's performance was thoroughly evaluated in several electrocatalytic reactions, such as methanol oxidation, oxygen evolution and reduction reactions, and hydrogen evolution. The results of this investigation reveal the impressive electrocatalytic ability of the Pt/C catalyst made from waste plastic. It was found to be comparable to the best commercially available Pt/C catalysts in all the reactions that were examined. This research not only demonstrates the possibility of using waste plastic for catalyst production, but also serves as the first documented example, based on successfully converting waste plastic bags into Pt/C through the conventional Liquid Phase Reduction (LPR) process. This novel method has great potential for sustainable and ecologically responsible catalytic applications. • The waste plastic derived Pt/C catalyst was prepared by solvothermal method. • For MOR plastic derived Pt/C shows electrocatalytic activity of 96.74 mA/cm2 current density and 46 % stability. • For OER it attain a current density of 10 mA/cm2 at a potential of 1.65 V. • For HER achieve current density of 10 mA/cm2 at a low voltage of 39.1 mV. • For ORR it exhibits −2.80 mA cm⁻2 of current density and half potential of 0.86 V. [ABSTRACT FROM AUTHOR]

Atomically dispersed active sites and hierarchical porosity in Fe–N–C catalyst materials are essential for efficient oxygen reduction reaction (ORR) electrocatalysis and effective mass transport, respectively. However, the majority of these catalysts fail to deliver outstanding electrocatalytic activity and stumble when used as cathode materials in fuel cells. Herein, we developed a catalyst with partially transformed metallic Fe into Fe-N x sites embedded in the carbonaceous matrix, and its excellent electrocatalytic performance is attributed to the hybrid nanoparticles and built-in Fe-N x site structures. The optimized Fe@Fe–N–C catalyst was tested for ORR performance both ex-situ using the rotating (ring)-disk electrode technique and in an anion exchange membrane fuel cell (AEMFC). The Fe@Fe–N–C electrocatalyst exhibited remarkably enhanced ORR activity in alkaline media with a half-wave potential of 0.822 V vs. reversible hydrogen electrode (RHE) and showed the maximum power density (P max) of 242 mW cm−2 in an AEMFC test, surpassing the peak power density obtained from the Pt/C cathode catalyst (P max = 220 mW cm−2) under H 2 –O 2 conditions. Therefore, the study provides a promising prospect for designing improved, cost-effective, and noble metal-free electrocatalysts for achieving high performance in AEMFCs. [Display omitted] • Hybrid Fe–N–C electrocatalysts with metallic Fe nanoparticles was developed. • A new strategy is proposed using melamine and N-hydroxysuccinimide to produce Fe–N–C. • The hybrid electrocatalyst with Fe and FeN x sites jointly promote the ORR activity. • The Fe@Fe–N–C cathode catalyst in AEMFC exhibits a peak power density of 242 mW cm−2. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) have emerged as a key technology in harnessing the potential of hydrogen energy. However, to fulfill the demands of efficient oxygen reduction kinetics, PEMFCs must exhibit exceptional capabilities in gas-liquid mass transfer, which is complex and challenging. This study draws inspiration from the structure of tongue skeletal muscle and mucosa, a biomimetic design for flow channel surface properties is proposed, and the intricate relationship between gas-liquid transport and cell performance is explored. Validate using experimental polarization curves and dynamic gas-liquid transport characteristics in the cathode flow channel. Results indicate that the hydrophilicity/hydrophobicity of channel walls significantly influences performance and flow characteristics. The biomimetic design outperforms conventional channels, demonstrating a 67.92% faster drainage. Notably, current density (CD) and peak power density (PD) reach 1258.0 mA/cm2 and 468.0 mW/cm2, respectively, highlighting effective performance enhancement and providing valuable insights for PEMFC optimization. • A wall wettability design inspired by the tongue skeletal muscle is proposed. • Comprehensive utilization of wall wettability can ensure uniform mass transfer. • The drainage rate of the bionic flow channel was increased by 67.92%. • The innovative work showing the 1258.0 mA/cm2 limited CD and 468.0 mW/cm2 peak PD. [ABSTRACT FROM AUTHOR]

The catalysts for oxygen reduction reaction (ORR) are of great significance to the development of electrochemical energy systems. In this paper, the ORR catalytic performance of Mn–Ni dual-metal doped N-coordinated graphene is studied by density functional theory (DFT). The results show that the catalysts with dual-metal active sites are more stable than that with single metal site, and all catalysts show certain catalytic activity. The reaction pathway analyses of catalysts with two different adsorption configurations of O 2 show that when O 2 is adsorbed on two metal sites, OOH will automatically split into OH and O. When O 2 is adsorbed on Mn site alone, the other site does not participate in the adsorption of oxygen-containing intermediates. The thermodynamic calculation results show that the catalytic performance is mainly influenced by the adsorption strength of O, which is controlled by the number of active sites involved in the adsorption, bond length and the number of transferred electrons at the active sites. The G-MnNiN 6 -3 shows the best catalytic performance with an overpotential of 0.453 V and a reaction energy barrier of 0.19 eV. The results of this study highlight the potential application of Mn–Ni dual-metal doped N-coordinated graphene as a highly efficient non-precious catalyst. • The ORR catalytic performance of Mn–Ni dual-metal doped N-coordinated graphene is studied for the first time. • The adsorption of O 2 can be classified into single adsorption and co-adsorption on bimetallic catalyst. • The catalytic performance is most affected by the adsorption strength of O. • The best catalyst shows the overpotential of 0.453 V and a reaction energy barrier of 0.19 eV. [ABSTRACT FROM AUTHOR]