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[Display omitted] The design and development of high-performance and long-life Pt-free catalysts for the oxygen reduction reaction (ORR) is of great important with respect to metal-air batteries and fuel cells. Herein, a new low-cost covalent organic frameworks (COFs)-derived Co N C single-atoms catalyst (SAC) is fabricated and compared with the engineered nanoparticle (NP) counterpart for ORR activity. The ORR performance of the SAC catalyst (Co SA @NC) surpasses the NP counterpart (Co NP -NC) under the same operation condition. Co SA @NC also achieves improved long-term durability and better methanol tolerance compared with the Pt/C. The zinc-air battery assembled by the Co SA @NC cathode delivers a higher power density and energy density than that of commercial Pt/C catalyst. Molecular dynamics (MD) is performed to explain the spontaneous evolution from clusters to single-atom metal configuration and density functional theory (DFT) calculations find that Co SA @NC possesses lower d -band center, resulting in weaker interaction between the surface and the O-containing intermediates. Consequently, the reductive desorption of OH*, the rate-determine step, is further accelerated. [ABSTRACT FROM AUTHOR]

The catalytic efficiency of the cathode is paramount in elevating the operational efficacy of low-temperature solid oxide fuel cells (LT-SOFCs) through expeditious facilitation of the oxygen reduction reaction (ORR). Cathode confronts formidable challenges due to oxygen reduction reaction (ORR) kinetics. This work aims to develop a high-performance cathode by doping strontium (Sr) into Nd 2- x Sr 2 x NiO 4. We synthesized a series of Nd 2- x Sr 2x NiO 4 (x : 0, 0.03, 0.06, 0.1) samples with varying Sr doping levels and evaluated their electrochemical performances. Nd2- x Sr 2 x NiO 4 with optimal ratio (x : 0.06) delivers the highest peak power density of 620–338 mw cm−2 at 550-470 °C among all four samples. The electrochemical impedance spectroscopy of the optimal composition revealed that Nd 2- x Sr 2 x NiO 4 exhibits low electrode polarization resistance of 0.34 Ω cm 2 , depicting its high catalytic performance and compatibility with the electrolyte and anode. Furthermore, XPS spectra also suggest higher surface oxygen vacancies than the other three samples, subsequently improving the conductivity and catalytic activity. Along with high power and OCVs, Nd 2- x Sr 2 x NiO 4 cathode-based SOFC is persistently stable for 40 h without significant degradation. These results conclusively point to demonstrating Nd 2- x Sr 2 x NiO 4 as a high-performing cathode for LT-SOFCs. [ABSTRACT FROM AUTHOR]

The influence of the heterogeneous interface is critical for the catalytic activity of the oxygen reduction reaction (ORR). This study demonstrates an enhancement of the electrocatalytic activity of the SrFe 0.9 Nb 0.1 O 3-δ (SFN113) electrode through the construction of a SrFe 0.9 Nb 0.1 O 3-δ -Sr 3 Fe 1.8 Nb 0.2 O 7-δ (SFN113-SFN327) heterogeneous interface. By coating varying amounts of Sr(NO 3) 2 (0.1 g, 0.2 g and 0.3 g) on SFN113 (1 g), SFN113/327 composite electrodes with different amounts of triple conducting oxide SFN327 are in-situ synthesized by high temperature calcination. Electrical Conductivity Relaxation (ECR) tests show that SFN327 has superior oxygen surface exchange performance compared to SFN113, especially at lower temperatures. At 550 °C, the oxygen surface exchange parameter of SFN327 is 4.23 times higher than that of SFN113. Symmetric cell tests with SFN113/327||BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.1 O 3-δ (BCZYYb)||SFN113/327 configuration and single cell tests with Ni-BCZYYb||BCZYYb||SFN113/327 configuration indicate that the SFN113/327 composite electrode with a mass ratio of 1:0.2 displays the best electrocatalytic performance, achieving a power output of 502 mW cm−2 at 700 °C. The work not only in-situ synthesizes the SFN113/327 triple conducting composite electrode, but also introduces a novel method for developing proton conducting electrode materials. [ABSTRACT FROM AUTHOR]

Double perovskite oxide Pr 1-x Nd x BaFe 2 O 5+δ (PNBFx, x = 0.0–0.3) nanofiber were prepared using electrospinning and were evaluated as cathodes for solid oxide fuel cells (SOFCs). The crystalline structure, microstructure, and electrochemical performance of PNBFx were thoroughly investigated and discussed. The PNBFx nanofiber cathodes obtained after sintering at 800 °C crystallized in a tetragonal structure with the space group P 4/ mmm and had good chemical compatibility with SDC electrolytes at 900 °C for 4 h. Nd doping was found to increase the lattice parameter, while the average valence of praseodymium and iron content increased steadily in PNBFx. The Pr 0.8 Nd 0.2 BaFe 2 O 5+δ (PNBF02) nanofiber cathode exhibited the best performance with a polarization resistance (R p) of 0.072 Ω cm2 at 750 °C. When PNBF02 nanofiber was used as a single-cell cathode, the peak power density reached 1.52 W cm2 at 750 °C. All results indicate that double perovskite PNBF02 is a promising cathode material for SOFCs. [ABSTRACT FROM AUTHOR]

With the incorporation of heteroatomic B into single-atom Fe catalyst (Fe SA -NC), a catalyst named Fe SA -BNC with a configuration of Fe-N 3 B 1 had been synthesized for the oxygen reduction reaction (ORR). The low electronegativity of B induced charge redistribution around the active center Fe, thereby modulating the ORR activity. The Fe SA -BNC catalyst demonstrated an outstanding ORR performance in alkaline conditions, with a half-wave potential of 0.87 V. [Display omitted] • Coordination of low electronegativity B with Fe atom. • Regulating the charge states of the active site Fe. • The decrease of the d -band center of Fe promoting the desorption of ORR intermediates and enhancing the ORR performance. Despite extensive research has been conducted on atomic dispersion catalysts for various reactions, altering the electronic structure of the central metal to enhance electrochemical reactivity remains a challenging task. Herein, the electrochemical reactivity was considerably enhanced by introducing heteroatomic B to adjust the d -band of single Fe center. In specific, the obtained Fe SA -BNC catalyst demonstrated an outstanding ORR performance (E 1/2 = 0.87 V) and exhibited greater long-term durability in alkaline media compared to Pt/C. The performance of Fe SA -BNC in Zn–air battery was also higher than that of Pt/C. According to theoretical calculations, a downward shift in the d -band center of Fe was induced by introducing B, thereby improving the desorption of intermediates and facilitating the oxygen reduction reaction (ORR). [ABSTRACT FROM AUTHOR]

Environmental pollution due to the excessive consumption of fossil fuels for energy production is a critical global issue. Fuel cells convert chemical energy directly into electricity in a clean and silent electrochemical process, but face challenges related to hydrogen storage, handling, and transportation. The direct borohydride fuel cell (DBFC), utilizing sodium borohydride as a liquid fuel, is a promising alternative to overcome such issues but requires the design of cost-effective nanostructured electrocatalysts. In this study, we synthesized nitrogen-doped graphene anchoring Ni nanoparticles (Ni@NG) by thermal degradation of polyethylene terephthalate bottle waste with urea and metallic Ni, and evaluated it as a sustainable carbon support. Electrocatalysts were prepared by incorporating ultralow amounts (0.09 to 0.27 wt.%) of Pd into the Ni@NG support. The resulting PdNi@NG electrocatalysts were characterized using ICP-OES, XPS, TEM, N2-sorption analysis, XRD, and Raman and FTIR spectroscopy. Voltammetry assessed the materials' electrocatalytic activity for oxygen reduction and borohydride oxidation reactions in alkaline media, corresponding to the anodic and cathodic reactions in DBFCs. The electrocatalyst with 0.27 wt.% Pd loading (PdNi_15@NG) exhibited the best performance for both reactions. Consequently, it was employed as an anodic and cathodic material in a lab-scale DBFC, achieving a specific power of 3.46 kW gPd−1. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) have received significant interest for optimizing metal atom utilization and superior catalytic performance in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this study, we investigate a range of single‐transition metal (STM1 = Sc1, Ti1, V1, Cr1, Mn1, Fe1, Co1, Ni1, Cu1, Zr1, Nb1, Mo1, Ru1, Rh1, Pd1, Ag1, W1, Re1, Os1, Ir1, Pt1, and Au1) atoms supported on graphyne (GY) surface for HER/OER and ORR using first‐principle calculations. Ab initio molecular dynamics (AIMD) simulations and phonon dispersion spectra reveal the dynamic and thermal stabilities of the GY surface. The exceptional stability of all supported STM1 atoms within the H1 cavity of the GY surface exists in an isolated form, facilitating the uniform distribution and proper arrangement of single atoms on GY. In particular, Sc1, Co1, Fe1, and Au1/GY demonstrate promising catalytic efficiency in the HER due to idealistic ΔGH* values via the Volmer‐Heyrovsky pathway. Notably, Sc1 and Au1/GY exhibit superior HER catalytic activity compared to other studied catalysts. Co1/GY catalyst exhibits higher selectivity and activity for the OER, with an overpotential (0.46 V) comparable to MoC2, IrO2, and RuO2. Also, Rh1 and Co1/GY SACs exhibited promising electrocatalysts for the ORR, with an overpotential of 0.36 and 0.46 V, respectively. Therefore, Co1/GY is a versatile electrocatalyst for metal‐air batteries and water‐splitting. This study further incorporates computational analysis of the kinetic potential energy barriers of Co1 and Rh1 in the OER and ORR. A strong correlation is found between the estimated kinetic activation barriers for the thermodynamic outcomes and all proton‐coupled electron transfer steps. We establish a relation for the Gibbs free energy of intermediates to understand the mechanism of SACs supported on STM1/GY and introduce a key descriptor. This study highlights GY as a favorable single‐atom support for designing highly active and cost‐effective versatile electrocatalysts for practical applications. [ABSTRACT FROM AUTHOR]

Here, an approach to produce a hierarchical porous Fe‐N‐C@TABOH catalyst with densely accessible high intrinsic active FeNx sites is proposed. The method involves a single‐step pyrolysis of Zn/Fe‐zeolitic imidazolate framework (Zn/Fe‐ZIF‐H) with tetrabutylammonium hydroxide (TABOH) micelles, which is obtained by utilizing TABOH as a structural template and electronic mediator at room temperature for a brief duration of 16 min. Notably, the yield of Zn/Fe‐ZIF‐H is 3.5 times that of Zn/Fe‐ZIF‐N prepared by conventional method. Results indicate that in addition to expediting synthesis and increasing yield of the Zn/Fe‐ZIF‐H, the TABOH induces a hierarchical porous structure and fosters the formation of more and higher intrinsic active FeNx moieties in Fex‐N‐C@TABOH, showing that TABOH is a multifunctional template. Crucially, the increased mesoporosity/external surface area and optimized microenvironment of Fe‐N‐C@TABOH significantly enhance ORR activity by facilitating the formation of high intrinsic active FeNx sites, increasing accessible FeNx sites, and reducing mass transfer resistance. Through structure tailoring and microenvironment optimization, the resulting Fe‐N‐C@TABOH exhibits superior ORR performance. DFT calculation further validates that the synergistic effect of these two factors leads to low ORR barrier and optimized *OH adsorption energy. This study underscores the importance of structure and electronic engineering in the development of highly active ORR catalysts. [ABSTRACT FROM AUTHOR]

Metal oxides containing La, Mn, and Co cations can catalyze oxygen reduction reactions (ORRs) in electrochemical processes. However, these materials require carbon support and optimal interactions between both compounds to be active. In this work, two approaches to prepare composites of La-Mn-Co-based compounds over carbon xerogel were developed. Using sol-gel methods, either the metal-based material was deposited on the existing carbon xerogel or vice versa. The metal oxide selected was the LaMn0.7Co0.3O3 perovskite, which has good catalytic behavior and selectivity towards direct ORRs. All the as-prepared composites were tested for ORRs in alkaline liquid electrolytes and characterized by diverse physicochemical techniques such as XRD, XPS, SEM, or N2 adsorption. Although the perovskite structure either decomposed or failed to form using those in situ methods, the materials exhibited great catalytic activity, which can be ascribed to the strengthening of the interactions between oxides and the carbon support via C-O-M covalent bonds and to the formation of new active sites such as the MnO/Co heterointerfaces. Moreover, Co-Nx-C species are formed during the synthesis of the metal compounds over the carbon xerogel. These species possess a strong catalytic activity towards ORR. Therefore, the composites formed by synthesizing metal compounds over the carbon xerogel exhibit the best performance in the ORR, which can be ascribed to the presence of the MnO/Co heterointerfaces and Co-Nx-C species and the strong interactions between both compounds. Moreover, the small nanoparticle size leads to a higher number of active sites available for the reaction. [ABSTRACT FROM AUTHOR]

Platinum-based intermetallic compounds (IMCs) play a vital role as electrocatalysts in a range of energy and environmental technologies, such as proton exchange membrane fuel cells. However, the synthesis of IMCs necessitates recombination of ordered Pt-M metallic bonds with high temperature driving, which is generally accompanied by side effects for catalysts' structure and performance. In this work, we highlight that semimetal atoms can trigger covalent interactions to break the synthesis-temperature limitation of platinum-based intermetallic compounds and benefit fuel-cell electrocatalysis. Attributed to partial fillings of p-block in semimetal elements, the strong covalent interaction of d-p π backbonding can benefit the recombination of ordered Pt-M metallic bonds (PtGe, PtSb and PtTe) in the synthesis process. Moreover, this covalent interaction in metallic states can further promote both electron transport and orbital fillings of active sites in fuel cells. The semimetal-Pt IMCs were obtained with a temperature 300 K lower than that needed for the synthesis of metal-Pt intermetallic compounds and reached the highest CO-tolerant oxygen reduction activity (0.794 A mg−1 at 0.9 V and 5.1% decay under CO poisoning) among reported electrocatalysts. We anticipate that semimetal-Pt IMCs will offer new insights for the rational design of advanced electrocatalysts for fuel cells. [ABSTRACT FROM AUTHOR]

Exploring highly active electrocatalysts as platinum (Pt) substitutes for the oxygen reduction reaction (ORR) remains a significant challenge. In this work, single Mn embedded nitrogen-doped graphene (MnN4) with and without halogen ligands (F, Cl, Br, and I) modifying were systematically investigated by density functional theory (DFT) calculations. The calculated results indicated that these ligands can transform the dyz and dxz orbitals of Mn atom in MnN4 near the Fermi-level into d z 2 orbital, and shift the d-band center away from the Fermi-level to reduce the adsorption capacity for reaction intermediates, thus enhancing the ORR catalytic activity of MnN4. Notably, Br and I modified MnN4 respectively with the lowest overpotentials of 0.41 and 0.39 V, possess superior ORR catalytic activity. This work is helpful for comprehensively understanding the ligand modification mechanism of single-atom catalysts and develops highly active ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] Developing an efficient and low-cost oxygen reduction electrocatalyst is essential for the application of aqueous zinc-air batteries (ZABs). Herein, we report a facile adsorption-confined pyrolysis strategy to fabricate the hybrid electrocatalyst (denoted as Co 9 S 8 /Co SA -PC) by embedding Co 9 S 8 nanoparticles into Co single atoms (Co-SAs) anchored porous carbon sheets for boosting oxygen reduction reaction (ORR) durability. In this strategy, the Co2+ ions are first absorbed into oxygen-rich porous carbon nanosheets and further form the Co-SAs with the help of thiourea in the following pyrolysis procedure, which is believed to be able to confine the generated Co 9 S 8 nanoparticles into carbon frameworks due to their interface interaction. Benefiting from the synergistic effect of different components, the obtained Co 9 S 8 /Co SA -PC electrocatalyst for ORR exhibits outstanding catalytic activity with a half-wave potential of 0.82 V and a distinguished long-term durability with a current retention of 80 % after cycling 80 h under alkaline conditions, which is superior to commercial Pt/C. Moreover, the assembled ZABs with Co 9 S 8 /Co SA -PC as cathodic catalyst deliver a high specific capacity of 764 mAh g Zn −1 at 10 mA cm−2 and the outstanding peak power density of up to 221.4 mW cm−2. This work provides a novel structure design strategy to prepare transition metal sulfide-based electrocatalysts with superior durability for ORR. [ABSTRACT FROM AUTHOR]

The advancement of economical and readily available electrocatalysts for the oxygen reduction reaction (ORR) holds paramount importance in the advancement of fuel cells and metal‐air batteries. Recently, 2D non‐metallic materials have obtained substantial attention as viable alternatives for ORR catalysts due to their manifold advantages, encompassing low cost, ample availability, substantial surface‐to‐volume ratio, high conductivity, exceptional durability, and competitive activity. The augmented ORR performances observed in metal‐free 2D materials typically arise from heteroatom doping, defects, or the formation of heterostructures. Here, the authors delve into the realm of electrocatalysts for the ORR, pivoting around metal‐free 2D materials. Initially, the merits of metal‐free 2D materials are explored and the reaction mechanism of the ORR is dissected. Subsequently, a comprehensive survey of diverse metal‐free 2D materials is presented, tracing their evolutionary journey from fundamental concepts to pragmatic applications in the context of ORR. Substantial importance is given on the exploration of various strategies for enhancing metal‐free 2D materials and assessing their impact on inherent material performance, including electronic properties. Finally, the challenges and future prospects that lie ahead for metal‐free 2D materials are underscored, as they aspire to serve as efficient ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

Rechargeable zinc-air batteries (ZABs) are regarded as a remarkably promising alternative to current lithium-ion batteries, addressing the requirements for large-scale high-energy storage. Nevertheless, the sluggish kinetics involving oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) hamper the widespread application of ZABs, necessitating the development of high-efficiency and durable bifunctional electrocatalysts. Here, we report oxygen atom-bridged Fe, Co dual-metal dimers (FeOCo-SAD), in which the active site Fe-O-Co-N6 moiety boosts exceptional reversible activity toward ORR and OER in alkaline electrolytes. Specifically, FeOCo-SAD achieves a half-wave potential (E1/2) of 0.87 V for ORR and an overpotential of 310 mV at a current density of 10 mA cm-2 for OER, with a potential gap (ΔE) of only 0.67 V Meanwhile, FeOCo-SAD manifests high performance with a peak power density of 241.24 mW cm-2 in realistic rechargeable ZABs. Theoretical calculations demonstrate that the introduction of an oxygen bridge in the Fe, Co dimer induced charge spatial redistribution around Fe and Co atoms. This enhances the activation of oxygen and optimizes the adsorption/desorption dynamics of reaction intermediates. Consequently, energy barriers are effectively reduced, leading to a strong promotion of intrinsic activity toward ORR and OER. This work suggests that oxygen-bridging dual-metal dimers offer promising prospects for significantly enhancing the performance of reversible oxygen electrocatalysis and for creating innovative catalysts that exhibit synergistic effects and electronic states. [ABSTRACT FROM AUTHOR]

Proton Exchange Membrane Fuel Cells (PEMFCs) represent a promising green solution for energy production, traditionally relying on platinum-group-metal (PGM) electrocatalysts. However, the increasing cost and limited global availability of PGMs have motivated extensive research into alternative catalyst materials. PGM-free oxygen reduction reaction (ORR) catalysts typically consist of first-row transition metal ions (Fe, Co) embedded in a nitrogen-doped carbon framework. Key factors affecting their efficacy include intrinsic activity and catalyst degradation. Thus, alternative materials with improved characteristics and the elucidation of reaction and degradation mechanisms have been the main concerns and most frequently explored research paths. High intrinsic activity and active site density can ensure efficient reaction rates, while durability towards corrosion, carbon oxidation, demetallation, and deactivation affects cell longevity. However, when moving to the actual application in PEMFCs, electrode engineering, which involves designing the catalyst layer, and other critical operational factors affecting fuel cell performance play a critical role. Electrode fabrication parameters such as ink formulation and deposition techniques are thoroughly discussed herein, explicating their impact on the electrode microstructure and formed electrochemical interface and subsequent performance. Adjusting catalyst loading, ionomer content, and porosity are part of the optimization. More specifically, porosity and hydrophobicity determine reactant transport and water removal. High catalyst loadings can enhance performance but result in thicker layers that hinder mass transport and water management. Moreover, the interaction between ionomer and catalyst affects proton conductivity and catalyst utilization. Strategies to improve the three-phase boundary through the proper ionomer amount and distribution influence catalyst utilization and water management. It is critical to find the right balance, which is influenced by the catalyst–ionomer ratio and affinity, the catalyst properties, and the layer fabrication. Overall, understanding how composition and fabrication parameters impact electrode properties and behaviour such as proton conductivity, mass transport, water management, and electrode–electrolyte interfaces is essential to maximize electrochemical performance. This review highlights the necessity for integrated approaches to unlock the full potential of PGM-free materials in PEMFC technology. Clear prospects for integrating PGM-free catalysts will drive cleaner and more cost-effective, sustainable, and commercially viable energy solutions. [ABSTRACT FROM AUTHOR]

The key factors in achieving high energy efficiency for proton exchange membrane fuel cells are reducing overpotential and increasing the oxygen reduction rate. Based on first-principles calculations, we induce H atom adsorption on 4 × 4 × 1 monolayer MoSe2 to induce spin polarization, thereby improving the catalytic performance. In the calculation of supercells, the band unfolding method is used to address the band folding effect in doped systems. Furthermore, it is evident from analyzing the unique energy band configuration of MoSe2 that a higher valley splitting value has better catalytic effects on the oxygen reduction reaction. We believe that the symmetries of the distinct adsorption site result in different overpotentials. In addition, when an even number of hydrogen atoms is adsorbed, the monolayer MoSe2 has no spin polarization. The spin can affect the electron transfer process and alter the hybrid energy with the reaction products, thereby regulating its catalytic performance. [ABSTRACT FROM AUTHOR]

[Display omitted] Solar light-driven hydrogen peroxide (H 2 O 2) production through the two-electron oxygen reduction reaction (ORR) from the earth-abundant O 2 and water is a potential alternative to the energy-consuming anthraquinone oxidation process, although the activity of the common photocatalysts is still insufficient to satisfy the industrial demands. Poor accessibility of O 2 to surface/interface and fast carrier recombination is the limiting-factor for catalytic systems. Herein, we develop a nanohybrid photocatalysts by introducing 1D conducting polymer of polypyrrole (PPy) nanotube on In 4 SnS 8 to promote H 2 O 2 evolution under visible light, obtaining up to 254.8 μM in 2 h, which is 2.4- and 13-fold larger than that of individual In 4 SnS 8 and PPy. The detailed characterizations of hybrid structure, O 2 adsorption behaviors, charge carrier dynamics over PPy/In 4 SnS 8 in conjunction with computational calculations corroborate that the modification of PPy could enlarge the amount of O 2 adsorption amount, expedite the cycle of O 2 adsorption/desorption and accelerate the transportation of electrons from In 4 SnS 8 to the interface, eventually speeding up H 2 O 2 photoproduction via indirect 2e− ORR pathway. This work establishes a paradigm of regulating the interfacial microenvironment by polymer for boosting H 2 O 2 photogeneration through high selectivity of ORR. [ABSTRACT FROM AUTHOR]

The unique properties of solid acid electrolytes, in particular CsH2PO4, are in many ways ideal for fuel cell operation. However, the technology is constrained by high cathode overpotentials. Here a simplified cathode geometry is employed to obtain the fundamental electrochemical parameters (exchange current density and charge transfer coefficient) describing the oxygen reduction reaction (ORR) at the CsH2PO4‐Pt‐gas interface. The parameters are incorporated into a 1D model of the voltage–current characteristics of realistic SAFC cathodes, which reproduced the measured polarization behavior of such cathodes without recourse to fitting adjustable parameters. Following this validation, the model is utilized to evaluate the impact of changes to cathode properties, microstructure, and operating conditions. Of these, the charge transfer coefficient, measured to have a value of ≈0.6 for ORR on Pt in the SAFC cathode environment, is found to have the greatest impact on power output. Nevertheless, even without material modifications, a combination of microstructural and operational modifications are identified with projected performance metrics meeting Department of Energy targets (0.8 V at 300 mA cm−2, and peak power density of 1 W cm−2), albeit at high Pt loadings. However, the analysis indicates that truly meaningful advances will likely necessitate the discovery of alternative ORR catalysts. [ABSTRACT FROM AUTHOR]

To alleviate the problems of environmental pollution and energy crisis, aggressive development of clean and alternative energy technologies, in particular, water splitting, metal–air batteries, and fuel cells involving two key half reactions comprising hydrogen evolution reaction (HER) and oxygen reduction (ORR), is crucial. In this work, an innovative hybrid comprising heterogeneous Cu/Co bimetallic nanoparticles homogeneously dispersed on a nitrogen-doped carbon layer (Cu/Co/NC) was constructed as a bifunctional electrocatalyst toward HER and ORR via a hydrothermal reaction along with post-solid-phase sintering technique. Thanks to the interfacial coupling and electronic synergism between the Cu and Co bimetallic nanoparticles, the Cu/Co/NC catalyst showed improved catalytic ORR activity with a half-wave potential of 0.865 V and an excellent stability of more than 30 h, even compared to 20 wt% Pt/C. The Cu/Co/NC catalyst also exhibited excellent HER catalytic performance with an overpotential of below 149 mV at 10 mA/cm2 and long-term operation for over 30 h. [ABSTRACT FROM AUTHOR]

Search for a Platinum metal-free catalyst for Proton Exchange Membrane Fuel Cells (PEMFCs) is a concern to scientists as the Pt-catalyzed electrode comprises about 45% of the entire fuel cell stack cost. Due to layered structure, Two-dimensional (2D) MoS2 nanostructured materials have recently drawn attention as effective catalysts for oxygen reduction reaction (ORR). The 1T-phase of MoS2 (1T-MoS2) has higher electronic conductivity than the 2H-phase (2H-MoS2); high surface area 1T-MoS2 can have high electrocatalytic activity towards PEFFCs. Here, we report hydrothermally synthesized 2H-MoS2 and solvothermally synthesized mixed 1T/2H-MoS2 phases as a catalyst for ORR in PEM Fuel Cells. Owing to the high BET-specific surface area, hybrid 1T/2H-MoS2 showed better ORR activity than 2H-MoS2. The limiting current density of the 1T/2H-MoS2 hybrid structure is ‒7.1 mA cm−2 compared to Pt/C (‒8.2 mA cm−2) at 1600 rpm. The Tafel slope values of 2H-MoS2, 1T/2H-MoS2, and Pt/C are 92.7 mV dec−1, 57.5 mV dec−1, and 39.3 mV dec−1, respectively. The electron transferred during ORR are 3.8 and 1.8, respectively, for 1T/2H-MoS2 and 2H-MoS2 (in 0.1 M KOH) ; suggesting less formation of undesirable peroxide formation than 2H-MoS2. The 1T/2H-MoS2 displays better electrochemical durability compared to 2H-MoS2 (after 2000 CV cycles). [ABSTRACT FROM AUTHOR]

[Display omitted] • A carboxylate linker strategy is proposed to construct atomically dispersed catalyst. • The OAc linker enhances the site density of accessible Fe-N 4 sites in Fe N C OAc. • The Fe N C OAc catalyst shows superior performance in both acidic and alkaline media. • Excellent performance are obtained in both liquid and solid-state Zn-air batteries. Iron-nitrogen-carbon single-atom catalysts derived from zeolitic-imidazolate-framework-8 (ZIF-8) have presented its great potential for the oxygen reduction reaction (ORR) in Zn-air batteries (ZABs). However, due to insufficient active Fe-N sites, its ORR activity is inferior to Pt-based catalysts. Herein, a carboxylate (OAc) linker strategy is proposed to design a ZIF-8-derived Fe N C OAc catalyst with abundant accessible Fe-N 4 single-atom sites. Except that imidazole groups can coordinate with Fe ions, the OAc linker on the unsaturated coordination Zn nodes can anchor and coordinate with more Fe ions, resulting in a significant increase in Fe-N 4 site density. Meanwhile, the corrosion of carbon skeleton by OAc oxidation during heat-treatment leads to improved porosity of catalyst. Benefitting from the highly dense Fe-N 4 sites and hierarchical pores, the Fe N C OAc endows superior performance in alkaline medium (E 1/2 = 0.906 V), which is confirmed by density functional theory calculation results. Meanwhile, the assembled liquid ZAB delivers a favorable peak power density of 173.9 mW cm−2, and a high specific capacity of 770.9 mAh g−1 as well as outstanding durability. Besides, the solid-state ZAB also shows outstanding discharge performance. [ABSTRACT FROM AUTHOR]

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FeN 3 -CoN 3 sites break the symmetric electron distribution of single atom sites optimizing adsorption energies of oxygen intermediates. As a result, FeCo-NC exhibits extraordinary ORR activity with a high half-wave potential of 0.915 V in alkaline electrolyte. [Display omitted] Single-atom catalysts show good oxygen reduction reaction (ORR) performance in metal-air battery. However, the symmetric electron distribution results in discontented adsorption energy of ORR intermediates and a lower ORR activity. Herein, Fe-Co dual-atom catalyst with FeN 3 -CoN 3 configuration was prepared by encapsulating nitrogen-rich ion (triethylenediamine cobalt complex, [Co(en) 3 ]3+) in Fe based MOF cage to greatly enhance ORR performance. Due to the confinement effect of the MOF cage, the encapsulated [Co(en) 3 ]3+ is closer to Fe of MOF, thus easily generating FeN 3 -CoN 3 sites. The FeN 3 -CoN 3 sites can break the symmetric electron distribution of single-atom sites, optimizing adsorption energy of oxygen intermediate. Thus, FeCo-NC exhibits extraordinary ORR activity with a high half-wave potential of 0.915 V and 0.789 V in alkaline and acidic electrolyte, respectively, while it was 0.874 V and 0.79 V for Pt/C. The liquid and solid Zn-air batteries with FeCo-NC as cathode show higher peak power density and specific capacity. DFT results indicate that FeN 3 -CoN 3 site can reduce the reaction energy barrier of the rate-determining step resulting in an excellent ORR performance. [ABSTRACT FROM AUTHOR]

[Display omitted] The development of efficient and cost-effective electrocatalysts to overcome the intrinsic sluggish kinetics of the oxygen reduction reaction (ORR) in zinc-air batteries is crucial. In this study, we introduce a strategy that integrates a template-assisted synthesis with subsequent thermal treatment to fabricate an active and stable cobalt-based nitrogen-doped carbon electrocatalyst, denoted as Co- N -CNT. The strategy adjusts the disordered architecture of the zeolitic imidazolate framework (ZIF) through the synergistic effect of bimetallic species, restricted the growth of zeolitic imidazolate framework nanoleaves (ZIF-L) using salt templates, and directed the transformation from a two-dimensional blade-like morphology to a three-dimensional multi-tiered composite structure. Notably, the Co- N -CNT-800 sample, synthesized at an optimized pyrolysis temperature of 800 °C, exhibits a half-wave potential of 0.89 V and demonstrates stability with sustained cycling over 21 h, which is comparable to the performance of commercial Pt/C electrocatalysts. Moreover, when employed as the cathode in zinc-air batteries, Co- N -CNT-800 not only surpasses Pt/C in terms of power density but also exhibits long-term charge/discharge stability. This findings offer a viable pathway for the design of active and cost-effective ORR electrocatalysts, holding promise for applications in the electrochemical energy storage and conversion systems. [ABSTRACT FROM AUTHOR]

[Display omitted] There are currently almost no ternary platinum-based nanosheets used for acidic oxygen reduction reactions (ORR) due to the difficulty in synthesizing ternary nanosheets with high Pt content. In this work, several ultrathin platinum-palladium-copper nanosheets (PtPdCu NSs) with a thickness of around 1.90 nm were prepared via a microwave heating-assisted method. Microwave heating allows a large number of Pt atoms to deposit into PdCu nanosheets, forming Pt-based ternary nanosheets with high Pt content. Among them, Pt 38 Pd 50 Cu 12 NSs catalyst displays the highest mass activity (MA) measured in 0.1 M HClO 4 of 0.932 A/mg Pt+Pd which is 8.6 times of that Pt/C. Besides, Pt 38 Pd 50 Cu 12 NSs catalyst also exhibits excellent stability with an extremely low MA attenuation after 80,000 cycles accelerated durability testing (ADT) tests. In the single cell tests, the Pt 38 Pd 50 Cu 12 NSs catalyst manifests higher maximum power density of 796 mW cm−2 than Pt/C of 606 mW cm−2. Density functional theory (DFT) calculations indicate the weaker adsorption between Pt and O-species in Pt 38 Pd 50 Cu 12 NSs leads to a significant enhancement of ORR activity. This study provides a new strategy to design and prepare ultrathin Pt-based trimetallic nanosheets as efficient and durable ORR catalysts. [ABSTRACT FROM AUTHOR]

In this paper, a novel soft template assisted strategy has been constructed to the size-tunable preparation of porous Cu−N−C/Surfactant catalysts successfully. The synergistic effects between the adjacent Cu ACs and atomically dispersed Cu-N 4 are favorable for manipulating the binding energy of O 2 adsorption and intermediates desorption at the atomic interface of catalysts, resulting in an excellent electrocatalytic oxygen reduction reaction (ORR) performance with a faster kinetics for Cu−N−C/F127 comparable to the commercially available Pt/C catalyst. [Display omitted] In this paper, a novel, simple and mild soft template assisted strategy and further carbonization approach has been constructed to the size-tunable preparation of porous Cu−N−C/Surfactant catalysts successfully. Note that the pluronic F127 has a significant influence on the synthesis of porous Cu−N−C/F127 with the atomically dispersed Cu-N 4 and adjacent Cu atomic clusters (ACs) than other surfactants owing to their particular non-ionic structure. By combining a series of experimental analysis and density functional theory (DFT) calculations, the synergistic effects between the adjacent Cu ACs and atomically dispersed Cu-N 4 are favorable for manipulating the binding energy of O 2 adsorption and intermediates desorption at the atomic interface of catalysts, resulting in an excellent electrocatalytic ORR performance with a faster kinetics for Cu−N−C/F127 than those of the Cu−N−C, Cu−N−C/CTAB, Cu−N−C/SDS, and comparable with the commercial Pt/C catalyst. This method not only provides a novel approach for synthesizing highly effective copper based single atom catalysts toward ORR, but also offers an in-depth understanding of the synergisms of adjacent ACs on the Cu single atoms (SAs) for highly effective electrocatalytic ORR and Zn-air Battery. [ABSTRACT FROM AUTHOR]

[Display omitted] The optimization of the adsorption of oxygen-containing intermediates on platinum (Pt) sites of Pt-based electrocatalysts is crucial for the oxygen reduction reaction process. Currently, a large amount of researches mainly focus on modifying the bulk structure of the electrocatalysts, however, the vital role of solvent effect on the phase interfaces is often overlooked. Here, we successfully developed an electrocatalyst in which the ordered PtCo alloy anchors on the cobalt (Co) single-atoms/clusters decorated support (Co 1,n N C) and its surface is further optimized using hydrophobic ionic liquid (IL). Experimental studies and theoretical calculations indicate that compressive stress on Pt lattice contributed by intrinsic structure and the local hydrophobicity caused by IL on the surface can suppress the stabilization of *OH on Pt. This synergistic effect affords outstanding catalytic performance, exhibiting a half-wave potential (E 1/2) of 0.916 V vs. RHE and a mass activity (MA) of 1350.3 mA mg Pt −1 in 0.1 mol/L perchloric acid (0.1 M HClO 4) electrolyte, much better than the commercial Pt/C (0.849 V vs. RHE and 145.5 mA mg Pt −1 for E 1/2 and MA, respectively). Moreover, the E 1/2 of IL-PtCo/Co 1,n N C only lost 5 mV after 10,000 cyclic voltammetry (CV) cycles due to a strong and synergistic contact of the intermetallic PtCo alloy with the Co 1,n N C support and IL. This research provides an effective method for designing efficient electrocatalysts by combining intrinsic structure and surface modification. [ABSTRACT FROM AUTHOR]

[Display omitted] Exploring precious metal-free bifunctional electrocatalysts for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is essential for the practical application of rechargeable Zn-air battery (ZAB). Herein, Ni-doped Co 9 S 8 nanoparticles embedded in a defect-rich N, S co-doped carbon matrix (d-Ni x Co 9-x S 8 @NSC) are synthesized via a facile pyrolysis and acid treatment process. The introduction of abundant defects in both the carbon matrix and metal sulfide provides numerous active sites and significantly enhances the electrocatalytic performances for both the ORR and OER. d-Ni x Co 9-x S 8 @NSC exhibits a superior half-wave potential of 0.841 V vs. RHE for the ORR and delivers a low overpotential of 0.329 V at 10 mA cm−2 for the OER. Additionally, Zn-air secondary battery using d-Ni x Co 9-x S 8 @NSC as the air cathode displays a higher specific capacity of 734 mAh g Zn −1 and a peak power density of 148.03 mW cm−2 compared to those of state-of-the-art Pt/C-RuO 2 (673 mAh g Zn −1 and 136.9 mW cm−2, respectively). These findings underscore the potential of d-Ni x Co 9-x S 8 @NSC as a high-performance electrocatalyst for secondary ZABs, offering new perspectives on the design of efficient noble metal-free electrocatalysts for future energy storage and conversion applications. [ABSTRACT FROM AUTHOR]

A Zn-air battery-driven SOR||HER coupling system based on a trifunctional P-CoMoO 4 /NF catalyst has been developed for self-powered synchronous sulfur recovery and hydrogen production. [Display omitted] • The self-driven SOR/HER hybrid electrolysis system was assembled for the first time. • P-CoMoO 4 /NF electrocatalysts were designed as three-dimensional catalyst for HER, SOR and ORR. • The sulfur-containing waste water can be recycled and H 2 generation occurs spontaneously. • The electrolysis can be realized without external energy consumption. This study introduces a self-driven system that effectively achieves synchronized sulfur recovery and hydrogen production using a Zn-air battery. The system ingeniously integrates the sulfur oxidation reaction (SOR) and the hydrogen evolution reaction (HER) into a single, efficient process. Central to this system is the trifunctional phosphorus-doped cobalt molybdate catalyst (P-CoMoO 4 /NF), which exhibits superior performance in both HER (η j = 100 = 0.13 V) and SOR (η j = 100 = 0.30 V) with remarkable stability (∼360 h), reaching 0.64 V at 100 mA cm−2 for simultaneous sulfur ion degradation and hydrogen production. Through density functional theory simulations and extensive characterizations, it has been shown that phosphorus doping in the cobalt molybdate catalyst facilitates electron redistribution, enhancing the catalyst's conductivity, generating more oxygen vacancies, and promoting improved mass and electron transfer. This modification also lowers the energy barrier for adsorbing reaction intermediates, thus increasing the hydrogen production rate and sulfur oxide conversion in this self-powered system. In summary, this research marks a substantial advancement in the development of trifunctional catalysts and proposes an eco-friendly, cost-effective strategy for integrated reaction systems, paving the way for sustainable energy solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] The electrocatalytic oxygen reduction reaction (ORR) is crucial for energy conversion systems such as fuel cells and metal-air batteries. Boron carbon nitrogen (BCN) is a novel functional material with a high specific surface area, excellent corrosion resistance, and outstanding electrochemical stability. These properties make BCN an effective ORR catalyst and a promising support for metal catalysts. This study leveraged the strong interaction between BCN and metals to anchor platinum nanoparticles (Pt NPs) onto the BCN surface (Pt/BCN), significantly enhancing the durability of traditional Pt/C catalysts in ORR. The half-wave potential of Pt/BCN is 0.927 V, higher than Pt/XC-72R (0.857 V) and commercial Pt/C (0.879 V). Notably, after 10,000 durability test cycles, the mass activity (MA) of Pt/XC-72R and commercial Pt/C decreased by 67 % and 75 %, respectively. Even after 50,000 cycles, Pt/BCN exhibited only a 54 % decrease in MA. Experimental data and density functional theory calculations confirmed increased electron transfer from Pt to the BCN support, indicating a strong electronic metal-support interaction (EMSI) between Pt and BCN. This strong EMSI effectively anchored the Pt NPs, preventing migration and aggregation during the ORR process. Consequently, our research introduces a novel electrocatalyst support material with significant potential for ORR and broader applications. [ABSTRACT FROM AUTHOR]

Novel Fe N C electrocatalysts derived from conjugated microporous polymers based on pre-functionalization of monomers was developed, which exhibits great potential for cathodic oxygen reduction reaction in fuel cell and provides a feasible strategy of developing multi-atoms doping catalysts for heterogeneous catalysis. [Display omitted] Porous iron–nitrogen-doped carbons (Fe N C) offer a great platform for construction of cathodic oxygen reduction reaction (ORR) catalysts in fuel cells. However, challenges still remain regarding with the collapse of carbon-skeleton during pyrolysis, uneven distribution of active sites and aggregation of metal atoms. In this work, we synthesized Fe, N co-doped conjugated microporous polymer (FeN-CMP) through a facile bottom-up strategy using 1,3,5-triethynylbenzene and iron-chelated 3,8-dibromo-1,10-phenanthroline as monomers, ensuring the uniform coordination of N with Fe element in network. Then, the resulting FeN-CMP was treated by pyrolysis without structural collapse to obtain porous Fe N C electrocatalyst for ORR. The most active catalyst was fabricated under 900 °C, which exhibits remarkable ORR activity in alkaline medium with half-wave potential of 0.796 V (18 mV and 105 mV positive deviation from the commercial Pt/C catalyst and post-doping catalyst), high selectivity with nearly 4e- transfer process and excellent methanol tolerance. Our study first developed porous Fe N C electrocatalysts derived from Fe, N -anchoring CMPs based on pre-functionalization of monomers, which exhibits great potential as an alternative to commercial Pt/C catalyst for ORR, and provides a feasible strategy of developing multi-atoms doping catalysts for energy storage and conversion as well as heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

We propose an in situ gas etching-thermal assembly strategy to simultaneously create mesopore-dominated carbon cores with ultrathin carbon-layer shells fully decorated with highly dispersed Mn-N 4 single-atom sites, which was used as a highly active and stable ORR catalyst in zinc-air batteries. [Display omitted] Applications of zinc-air batteries are partially limited by the slow kinetics of oxygen reduction reaction (ORR); Thus, developing effective strategies to address the compatibility issue between performance and stability is crucial, yet it remains a significant challenge. Here, we propose an in situ gas etching-thermal assembly strategy with an in situ -grown graphene-like shell that will favor Mn anchoring. Gas etching allows for the simultaneous creation of mesopore-dominated carbon cores and ultrathin carbon layer shells adorned entirely with highly dispersed Mn-N 4 single-atom sites. This approach effectively resolves the compatibility issue between activity and stability in a single step. The unique core–shell structure allows for the full exposure of active sites and effectively prevents the agglomerations and dissolution of Mn-N 4 sites in cores. The corresponding half-wave potential for ORR is up to 0.875 V (vs. reversible hydrogen electrode (RHE)) in 0.1 M KOH. The gained catalyst (Mn-N@Gra-L)-assembled zinc-air battery has a high peak power density (242 mW cm−2) and a durability of ∼ 115 h. Furthermore, replacing the zinc anode achieved a stable cyclic discharge platform of ∼ 20 h at varying current densities. Forming more fully exposed and stable existing Mn-N 4 sites is a governing factor for improving the electrocatalytic ORR activity, significantly cycling durability, and reversibility of zinc-air batteries. [ABSTRACT FROM AUTHOR]

Reversible protonic ceramic electrochemical cell (R-PCEC) has demonstrated high potential as an energy storage and conversion device. Efforts have primarily concentrated on the development of oxygen electrodes being to increase their performance and reduce performance degradation. In this work, three perovskite materials, namely Ba 0.9 Co 0.2 Fe 0.7 Nb 0.1 O 3-δ (BCFN), Ba 0.8 La 0.1 Co 0.2 Fe 0.7 Nb 0.1 O 3-δ (BLCFN), and Ba 0.8 La 0.1 Co 0.2 Fe 0.7 Nb 0.1 F 0.1 O 2.9-δ (BLCFNF) are investigated. Both doping with La and co-doping with La and F lead to a notable reduction in the average valence states of Fe, Co, and Nb elements, further resulting in an increase in oxygen vacancy concentration, thereby enhancing the oxygen migration ability of the material. The H 2 O partial pressure does not have a significant impact on the polarization resistance (R p) of the oxygen electrode. Conversely, the rise in R p is highly correlated with the decrease in oxygen partial pressure, suggesting that the primary factor influencing the reaction rate of the oxygen electrode process is the exchange of oxygen ions on the surface of the electrode. BLCFNF exhibits the best oxygen migration and surface exchange ability, resulting in the lowest R p. When BLCFNF was used as the oxygen electrode in a R-PCEC with the humidity air (10%H 2 O) and humidified H 2 (3%H 2 O) as oxidant and fuel, respectively, it exhibits the highest maximum power density of 472 mW cm−2, and a current density of −682.6 mA cm−2 (1.3 V) at 650 °C. In addition, BLCFNF also shows good durability in both discharge and electrolysis process. The results indicate that La and F co-doped BLCFNF material is a promising oxygen electrode material for R-PCECs. [ABSTRACT FROM AUTHOR]

Achieving high performance and stability in cathodes for the oxygen reduction reaction is crucial for the advancement of proton ceramic fuel cells (PCFCs). The introduction of non-metal doping method presents an opportunity to simultaneously optimize the perovskite structure and augment the activity and stability of the oxygen reduction reaction. Herein, we develop a phosphorus-doped SrCo 0·8 Fe 0·15 P 0·05 O 3-δ (SCFP) cathode for PCFCs. The SCFP cathode shows a low area specific resistance of 0.24 Ω cm2 at 650 °C in wet air (5% H 2 O), which is smaller than that of the phosphorus-free SrCo 0·8 Fe 0·2 O 3-δ (SCF) electrode (0.34 Ω cm2). The Ni–BaZr 0.1 Ce 0·7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) anode-supported single cell with BZCYYb electrolyte and SCFP cathode exhibits a superior performance of 865 mW cm−2 at 650 °C under H 2 atmosphere. This underscores the effectiveness of the phosphorus-doping strategy as a promising approach for advancing cathode development in PCFCs. [Display omitted] [ABSTRACT FROM AUTHOR]

Ammonia (NH 3), a promising carbon-free energy carrier, can be directly and efficiently converted into electricity in solid oxide fuel cells (SOFCs). However, the NH 3 -fueled SOFC (NH 3 –SOFC) still suffered from several difficulties, including sluggish oxygen reduction reaction (ORR) kinetics and poor cathode durability. In this study, we develop a LSCF-GDC dual-phase cathode with uniform distribution for NH 3 –SOFC. In comparison with commercial counterpart, the dual-phase cathode shows a lower ORR resistance of 0.114 Ω cm2 for at 700 °C due to reduced grain sizes and expanded triple-phase boundary (TPB) length. The resultant NH 3 –SOFC follows the H 2 oxidation process and delivers a comparable peak power density of 0.347 Wcm−2 to H 2 –SOFC at 700 °C, which is further improved to 0.516 Wcm−2 after 280 h activation at 0.7 V. Further operation of five thermal cycles between 700 and 500 °C results in a performance degradation, which can be explained by the microstructure changes of Ni-based anode rather than the dual-phase cathode. Moreover, the thermal cycled NH 3 –SOFC can maintain stable operation without current decay at constant 700 °C and 0.7 V in the subsequent 135 h, further demonstrating the robustness of the dual-phase cathode. Therefore, the introduction of GDC into self-assembled dual-phase cathode is an effective way to synergistically promote the electrochemical activity and durability of the cathode for NH 3 –SOFC. [ABSTRACT FROM AUTHOR]

[Display omitted] The rational construction of highly active and robust non-precious metal oxygen reduction electrocatalysts is a vital factor to facilitate commercial applications of Zn-air batteries. In this study, a precise and stable heterostructure, comprised of a coupling of Co 3 Fe 7 and Fe 3 C, was constructed through an interface engineering-induced strategy. The coordination polymerization of the resin with the bimetallic components was meticulously regulated to control the interfacial characteristics of the heterostructure. The synergistic interfacial effects of the heterostructure successfully facilitated electron coupling and rapid charge transfer. Consequently, the optimized CST-FeCo displayed superb oxygen reduction catalytic activity with a positive half-wave potential of 0.855 V vs. RHE. Furthermore, the CST-FeCo air electrode of the liquid zinc-air battery revealed a large specific capacity of 805.6 mAh g Zn -1, corresponding to a remarkable peak power density of 162.7 mW cm−2, and a long charge/discharge cycle stability of 220 h, surpassing that of the commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] The sluggish kinetics and inferior stability of oxygen electrocatalyst in rechargeable zinc air battery (ZAB) hamper its industrialization. In this work, we activate cobalt telluride (CoTe) by introduction of metallic cobalt (Co) to modulate the work function to facilitate the electron transfer from Co to CoTe during oxygen catalysis; additionally, the three-dimensional porous carbon nanosheets (3DPC) are invited to reduce the resistance towards electrolyte/oxygen diffusion. Thereby, Co-CoTe@3DPC only demands 280 mV overpotential to reach 10 mA cm−2 under alkaline oxygen evolution reaction (OER) condition, relatively lower than commercial iridium oxides (IrO 2); besides, the operando electrochemical impedance spectroscopy (EIS) indicates a better resistance towards surface reconstruction than Co@3DPC leading to a superior stability. A Pt-like oxygen reduction reaction (ORR) performance, half-wave potential associated with kinetic current density, is achieved for Co-CoTe@3DPC. A maximum power density of 203 mW cm−2 is achieved and sustains for 800 h. Furthermore, the all-solid-state ZAB offers 97 mW cm−2. Theoretical calculation suggests that the incorporation of metallic Co to CoTe maintains the superb ORR activity and promotes the OER catalysis. [ABSTRACT FROM AUTHOR]

We introduce N-P pair into the carbon matrix to construct N,P-C electrocatalyst by a facile pyrolysis strategy. Benefiting from the moderate adsorption energy of *OH on the active sites (C adjacent to P atom in N-P), the achieved N,P-C-1000 displays outstanding alkaline ORR performance and high power density primary liquid and solid ZABs. [Display omitted] • N-P pair was introduced into the carbon matrix to construct N,P-C electrocatalyst by a facile pyrolysis strategy. • The catalyst exhibits superior ORR activity with a E 1/2 of 0.83 V, comparable to that of commercial 20 wt% Pt/C. • Its C-2p orbit has higher interaction strength with the intermediates, thus reducing the overall reaction energy barrier. • High power density primary liquid and solid ZABs are achieved using N,P-C-1000 as cathodic catalysts. Developing sustainable metal-free carbon-based electrocatalysts is essential for the deployment of metal-air batteries such as zinc-air batteries (ZABs), among which doping of heteroatoms has attracted tremendous interest over the past decade. However, the effect of the heteroatom covalent bonds in carbon matrix on catalysis was neglected in most studies. Here, an efficient metal-free oxygen reduction reaction (ORR) catalyst is demonstrated by the N-P bonds anchored carbon (termed N,P-C-1000). The N,P-C-1000 catalyst exhibits superior specific surface area of 1362 m2 g−1 and ORR activity with a half-wave potential of 0.83 V, close to that of 20 wt% Pt/C. Theoretical computations reveal that the p-band center for C-2p orbit in N,P-C-1000 has higher interaction strength with the intermediates, thus reducing the overall reaction energy barrier. The N,P-C-1000 assembled primary ZAB can attain a large peak power density of 121.9 mW cm−2 and a steady discharge platform of ∼1.20 V throughout 120 h. Besides, when served as the cathodic catalyst in a solid-state ZAB, the battery shows flexibility, conspicuous open circuit potential (1.423 V), and high peak power density (85.8 mW cm−2). Our findings offer a strategy to tune the intrinsic structure of carbon-based catalysts for improved electrocatalytic performance and shed light on future catalysts design for energy storage technologies beyond batteries. [ABSTRACT FROM AUTHOR]

Coordination environment engineering is developed to synthesize Fe SA /NSC catalysts with the tailored N, S co-coordinated Fe atomic site. [Display omitted] • The Fe-N 3 S active site with the optimized electronic structure is constructed. • S doping promotes the OH* desorption, thus leading to enhanced kinetics process. • The catalyst displays impressive ORR activity in both alkaline and acidic mediums. • The catalyst exhibits excellent performance in Zn-air batteries and fuel cells. Atomically dispersed iron–nitrogen-carbon (FesbndNsbndC) materials have been considered ideal catalysts for the oxygen reduction. Unfortunately, designing and adjusting the electronic structure of single-atom Fe sites to boost the kinetics and activity still faces grand challenges. In this work, the coordination environment engineering is developed to synthesize the Fe SA /NSC catalyst with the tailored N, S co-coordinated Fe atomic site (Fe-N 3 S site). The structural characterizations and theoretical calculations demonstrate that the incorporation of sulfur can optimize the charge distribution of Fe atoms to weaken the adsorption of OH* and facilitate the desorption of OH*, thus leading to enhanced kinetics process and intrinsic activity. As a result, the S-modified Fe SA /NSC exhibits outstanding catalytic activity with the half-wave potentials (E 1/2) of 0.915 V and 0.797 V, as well as good stability, in alkaline and acidic electrolytes, respectively. Impressively, the excellent performance of Fe SA /NSC is further confirmed in Zn-air batteries (ZABs) and fuel cells, with high peak power densities (146 mW cm−2 and 0.259 W cm−2). [ABSTRACT FROM AUTHOR]

Traditional energy resource, i.e. coal, is converted to value-added electrode materials in electrochemical energy conversion systems. [Display omitted] • Traditional coal energy resource is converted to value-added electrode material for electrochemical energy conversion system. • The intrinsic N- and S-heteroatoms in coal effectively enhance the ORR performance. • The electrode exhibited excellent performance in Zn-air batteries with both liquid and solid electrolytes. Coal-based oxygen electrocatalysts hold immense promise for cost-effective applications in rechargeable Zn-air batteries (ZABs) and the value-added, clean utilization of traditional coal resources. Herein, an electrospun membrane electrode comprising coal-derived carbon nanosheets and directly grown carbon nanotubes (CNS/CMF@CNT) was successfully synthesized. The hierarchical porous structure of the electrode, composed of multiple components, significantly facilitates mass and ion transportation, resulting in exceptional electrochemical performance. Employing Fe as the catalyst for CNT growth, the CNS/CMF@CNT electrode exhibits a remarkable onset potential of 0.96 V and a half-wave potential of 0.87 V in the oxygen reduction reaction (ORR). In-situ surface-enhanced Raman spectroscopy reveals that hydroxyl radical desorption on the surface of CNS/CMF@CNT(Fe) is the rate-determining step of the ORR. Notably, the aqueous ZAB featuring the CNS/CMF@CNT(Fe) electrode achieved a peak power density of 216.0 mW cm−2 at a current density of 414 mA cm−2 and maintained a voltage efficiency of 65.1 % after 2000 charge/discharge cycles at 5 mA cm−2. Furthermore, the all-solid-state ZAB incorporating this electrode displayed an open-circuit voltage of 1.43 V, a peak power density of 70.1 mW cm−2 at a current density of 110 mA cm−2, and a voltage efficiency of 66.5 % after 150 charge/discharge cycles. The utilization of abundant coal as the raw material for electrode fabrication not only brings conceivable economic benefits in ZAB construction, but also commendably advances the effective application of traditional coal resources in a more sustainable manner. [ABSTRACT FROM AUTHOR]

Abstract Non-precious electrocatalysts as the alternative to Pt have become a hot research area in the last decade due to the suitable catalytic activity in Oxygen reduction reaction (ORR) in electrochemical systems. In this work, the density functional theory calculations were investigated to explore the activity of Fe, Cu, and Fe-Cu atoms supported by N-doped graphene as the ORR electrocatalyst for Oxygen-depolarized cathodes (ODCs). To this end, the ORR mechanism was surveyed in detail in the gas and solvent phases. The results show that the solvent phase leads to a higher overpotential and thermodynamic limiting potential. According to the density of states curves, there are strong interactions between metal atom and substrate that can effectively tune the electronics of catalysts. Bader's analysis confirms that, in addition to the single metal atoms, nitrogen atoms have also played a critical role in charge transfer between substrates and oxygen molecules in ORR. It is also predicted that Fe-Cu@NC SAC exhibits the highest catalytic activity which is consistent with thermodynamic limiting potential and theoretical overpotential of − 0.26 and 0.66 (V vs. SHE), respectively, indicating that this type of catalyst may be a suitable candidate instead of precious metals in oxygen-depolarized cathodes in electrochemical devices.

Abstract Covalent organic frameworks (COFs) have been utilized as the ideal candidates to preciously construct electrocatalysts. However, the highly ordered degree of COFs renders the catalytic centers closely stacked, which limits the utilization efficiency of catalytic sites. Herein, we have first constructed dangling and staggered‐stacking aldehyde (–CHO) from [4 + 3] COFs as catalytic centers for 2e− oxygen reduction reaction (ORR). The new catalytic COFs have unreacted dangling ‐CHO out of the COFs' planes, which are more easily exposed in electrolytes than the sites in the frameworks. More importantly, these –CHO adopt staggered stacking models, and thus provide larger space for mass transport than those with eclipsed stacking models. In addition, by tuning the triratopic linkers in the COFs, the catalytic properties are well modulated. The optimized COF shows high selectivity and activity for 2e− ORR, with H2O2 selectivity of 91%, and mass activity of 12.2 A g−1, respectively. The theoretical calculation further reveals the higher activity for the pyridine‐contained B18C6‐PTTA‐COF due to the promoted binding ability of the intermediate OOH* at the carbon in dangling –CHO. This work provides us with a new insight into designing electrocatalysts based on COFs.

Highlights A novel A/B-sites co-substitution strategy was introduced to enhance the performance and durability of Ruddlesden–Popper perovskite Sr3Fe2O7−δ (SF)-based air electrodes for reversible protonic ceramic cells (RePCCs). Simultaneous Sr-deficiency and Nb-substitution in SF result in Sr2.8Fe1.8Nb0.2O7−δ (D-SFN), offering improved structural stability under RePCC conditions by suppressing the formation of Sr3Fe2(OH)12 phase. The introduction of Sr-deficiency enhances oxygen vacancy concentration in D-SFN, promoting efficient oxygen transport within the material and contributing to excellent activity in RePCCs.

Oxygen reduction reaction (ORR) and oxygen evolutionc reaction (OER) are important chemical reactions for a rechargeable lithium–oxygen battery (LOB). Recently, high-entropy alloys and oxides have attracted much attention because they showed good electrocatalytic performance for oxygen evolution reaction (OER) and/or oxygen reduction reaction (ORR). In this study, we aimed to synthesize and characterize CoSn(OH)6 and two types of high-entropy perovskite hydroxides, that is, (Co0.2Cu0.2Fe0.2Mn0.2Mg0.2)Sn(OH)6 (CCFMMSOH) and (Co0.2Cu0.2Fe0.2Mn0.2Ni0.2)Sn(OH)6 (CCFMNSOH). TEM observation and XRD measurements revealed that the high-entropy hydroxides CCFMMSOH and CCFMNSOH had cubic crystals with sides of approximately 150–200 nm and crystal structures similar to those of perovskite-type CSOH. LSV measurement results showed that the high-entropy hydroxides CCFMMSOH and CCFMNSOH showed bifunctional catalytic functions for the ORR and OER. CCFMNSOH showed better catalytic performance than CCFMMSOH. [ABSTRACT FROM AUTHOR]

The sluggish kinetics of oxygen reduction reactions (ORRs) require considerable Pd in the cathode, hindering the widespread of alkaline fuel cells (AFCs). By alloying Pd with transition metals, the oxygen reduction reaction's catalytic properties can be substantially enhanced. Nevertheless, the utilization of Pd-transition metal alloys in fuel cells is significantly constrained by their inadequate long-term durability due to the propensity of transition metals to leach. In this study, a nonmetallic doping strategy was devised and implemented to produce a Pd catalyst doped with P that exhibited exceptional durability towards ORRs. Pd3P0.95 with an average size of 6.41 nm was synthesized by the heat-treatment phosphorization of Pd nanoparticles followed by acid etching. After P-doping, the size of the Pd nanoparticles increased from 5.37 nm to 6.41 nm, and the initial mass activity (MA) of Pd3P0.95/NC reached 0.175 A mgPd−1 at 0.9 V, slightly lower than that of Pd/C. However, after 40,000 cycles of accelerated durability testing, instead of decreasing, the MA of Pd3P0.95/NC increased by 6.3% while the MA loss of Pd/C was 38.3%. The durability was primarily ascribed to the electronic structure effect and the aggregation resistance of the Pd nanoparticles. This research also establishes a foundation for the development of Pd-based ORR catalysts and offers a direction for the future advancement of catalysts designed for practical applications in AFCs. [ABSTRACT FROM AUTHOR]

We explored two methods for synthesizing Pd nanoparticles using three different carbide-derived carbon (CDC) support materials, one of which was nitrogen-doped. These materials were studied for oxygen reduction reaction (ORR) in 0.1 M KOH solution, and the resulting CDC/Pd catalysts were characterized using TEM, XRD, and XPS. The citrate method and the polyol method using polyvinylpyrrolidone (PVP) as a capping agent were employed to elucidate the impact of the support material on the final catalyst. The N-doping of the CDC material resulted in smaller Pd nanoparticles, but only in the case of the citrate method. This suggests that the influence of support is weaker when using the polyol method. The citrate method with CDC1, which is predominantly microporous, led to a higher degree of agglomeration and formation of larger particles in comparison to supports, which possessed a higher degree of mesoporosity. We achieved smaller Pd particle sizes using citrate and NaBH4 compared to the ethylene glycol PVP method. Pd deposited on CDC2 and CDC3 supports showed similar specific activity (SA), suggesting that the N-doping did not significantly influence the ORR process. The highest SA value was observed for CDC1/Pd_Cit, which could be attributed to the formation of larger Pd particles and agglomerates. [ABSTRACT FROM AUTHOR]

[Display omitted] Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential for the development of excellent bifunctional electrocatalysts, which are key functions in clean energy production. The emphasis of this study lies in the rapid design and investigation of 153 MN 4 –graphene (Gra)/ MXene (M 2 NO) electrocatalysts for ORR/OER catalytic activity using machine learning (ML) and density functional theory (DFT). The DFT results indicated that CoN 4 –Gra/Ti 2 NO had both good ORR (0.37 V) and OER (0.30 V) overpotentials, while TiN 4 –Gra/M 2 NO and MN 4 –Gra/Cr 2 NO had high overpotentials. Our research further indicated orbital spin polarization and d-band centers far from the Fermi energy level, affecting the adsorption energy of oxygen-containing intermediates and thus reducing the catalytic activity. The ML results showed that the gradient boosting regression (GBR) model successfully predicted the overpotentials of the monofunctional catalysts RhN 4 –Gra/Ti 2 NO (ORR, 0.39 V) and RuN 4 –Gra/W 2 NO (OER, 0.45 V) as well as the overpotentials of the bifunctional catalyst RuN 4 –Gra/W 2 NO (ORR, 0.39 V; OER, 0.45 V). The symbolic regression (SR) algorithm was used to construct the overpotential descriptors without environmental variable features to accelerate the catalyst screening and shorten the trial-and-error costs from the source, providing a reliable theoretical basis for the experimental synthesis of MXene heterostructures. [ABSTRACT FROM AUTHOR]

[Display omitted] Lignin upgrading to various functional products is promising to realize high-value utilization of low-cost and renewable biomass waste, but is still in its infancy. Herein, using industry waste lignosulfonate as the biomass-based carbon source and urea as the dopant, we constructed a heteroatom-doped porous carbon nanosheet structure by a simple NaCl template-assisted pyrolytic strategy. Through the synergistic effect of the NaCl template and urea, the optimized lignin-derived porous carbon catalyst with high content of active nitrogen species and large specific surface area can be obtained. As a result, the fabricated catalysts exhibited excellent electrocatalytic oxygen reduction activity, as well as good methanol tolerance and stability, comparable to that of commercial Pt/C. Moreover, rechargeable Zn-air batteries assembled with this electrocatalyst have a peak power density of up to 150 mW cm-2 and prominent long-term cycling stability. This study offers an inexpensive and efficient way for the massive production of highly active metal-free catalysts from the plentiful, inexpensive and environmentally friendly lignin, offering a good direction for biomass waste recycling and utilization. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2D GnP/MoS 2 and 3D (GnP/MoS 2)/MWNT composites are prepared by a facile, robust and ecofriendly method. • Effects of N-doping of GnPs and mass fraction of MWNTs on ORR activity are explored and rationalized. • Best synergistic ORR activity is obtained for N-doped catalyst with 3:1 2D-to-1D ratio. • Catalysts exhibit excellent stability and methanol resistance in alkaline medium. • Promising route to develop bifunctional ORR/OER catalysts. Nanocomposites have garnered attention for their potential as catalysts in electrochemical reactions vital for technologies like fuel cells, water splitting, and metal-air batteries. This work focuses on developing three-dimensional (3D) nanocomposites through aqueous phase exfoliation, non-covalent functionalization of building blocks with surfactants and polymers, and electrostatic interactions in solution leading to the nanocomposites assembly and organization. By combining molybdenum disulfide (MoS 2) layers with graphene nanoplatelets (GnPs) to form a binary 2D composite (MoS 2 /GnP), and subsequently incorporating multiwalled carbon nanotubes (MWNTs) to create ternary 3D composites, we explore their potential as catalysts for the oxygen reduction reaction (ORR) critical in fuel cells. Characterization techniques such as X-ray photoelectron spectroscopy, scanning electron microscopy, and X-ray diffraction elucidate material composition and structure. Our electrochemical studies reveal insights into the kinetics of the reactions and structure–activity relationships. Both the (MoS 2 /GnP)-to-MWNT mass ratio and nitrogen-doping of GnPs (N -GnPs) play a key role on the electrocatalytic ORR performance. Notably, the (MoS 2 / N -GnP)/MWNT material, with a 3:1 mass ratio, exhibits the most effective ORR activity. All catalysts demonstrate good long-term stability and methanol crossover tolerance. This facile fabrication method and observed trends offer avenues for optimizing composite electrocatalysts further. [ABSTRACT FROM AUTHOR]

In this study, Co/Ni‐NC catalyst with hetero‐diatomic Co/Ni active sites dispersed on nitrogen‐doped carbon matrix is synthesized via the controlled pyrolysis of ZIF‐8 containing Co2+ and Ni2+ compounds. Experimental characterizations and theoretical calculations reveal that Co and Ni are atomically and uniformly dispersed in pairs of CoN4‐NiN4 with an intersite distance ≈0.41 nm, and there is long‐range d–d coupling between Co and Ni with more electron delocalization for higher bifunctional activity. Besides, the in situ grown carbon nanotubes at the edges of the catalyst particles allow high electronic conductivity for electrocatalysis process. Electrochemical evaluations demonstrate the superior ORR and OER bifunctionality of Co/Ni‐NC catalyst with a narrow potential gap of only 0.691 V and long‐term durability, significantly prevailing over the single‐atom Co‐NC and Ni‐NC catalysts and the benchmark Pt/C and RuO2 catalysts. Co/Ni‐NC catalyzed Zn–air batteries achieve a high specific capacity of 771 mAh g−1 and a long continuous operation period up to 340 h with a small voltage gap of ≈0.65 V, also much superior to Pt/C‐RuO2. [ABSTRACT FROM AUTHOR]