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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]

Carbon nanomaterials doped with N and B could activate nearby carbon atoms to promote charge polarization through the synergistic coupling effect between N and B atoms, thus facilitating adsorption of O2 and weakening O−O bond to enhance oxygen reduction reaction. Herein, a simple and controllable self‐assembly strategy is applied to synthesize porous B, N co‐doped carbon‐based catalysts (BCN‐P), which employs the macrocyclic molecule cucurbit[7]uril (CB7) as nitrogen source, and 3D aromatic‐like closo‐[B12H12]2− as boron source. In addition, polystyrene microspheres are added to help introduce porous structure to expose more active sites. Benefitting from porous structures and the synergistic coupling effect between N and B atoms, BCN‐P has a high onset potential (Eonset=0.846 V) and half‐wave potential (E1/2=0.74 V) in alkaline media. The zinc‐air battery assembled with BCN‐P shows high operating voltage (1.42 V), peak power density (128.7 mW cm−2) and stable charge/discharge cycles, which is even comparable with Pt/C. [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]

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]

Obstacles in the pathway of sustainable energy production basically inspire the researchers to fabricate efficient and stable multifunctional electrocatalysts to speed-up the sluggish kinetics of oxygen reduction reaction (ORR), along with oxygen and hydrogen evolution reactions (OER and HER). For that, we developed a high performing electrocatalyst for ORR, OER, and HER via uniform dispersion of ruthenium nanoparticles on a nitrogen-phosphorous-doped ultrathin carbon matrix (Ru@N–P–C) via pyrolysis. Doped intrinsic heteroatoms (N and P) allowed for the co-existence of graphitic lattice carbons along with amorphous carbon, which aided in the uniform distribution of Ru NPs over the carbon matrix, thereby, facilitating the efficient electron transfer, forming synergistic effect, and suppressing agglomeration of Ru NPs. The constructed Ru@N–P–C heterostructure, prepared at 800 °C, displayed low overpotentials of 45 mV for HER and 327 mV for OER at the current density of 10 mA/cm2, with a Tafel slope value of 115 and 66 mV/dec in alkaline medium, respectively. Furthermore, as-constructed Ru@N–P–C exhibited similar ORR activities to the standard 20% Pt/C catalyst. Besides, Ru@N–P–C heterostructure shows excellent stability during all the ORR, OER, and HER processes, which further suggest its practical applications. Thus, this research paves the way for creating cutting-edge electrocatalysts for energy-related electrocatalysis. • Electrocatalyst (Ru@N–P–C) nanosheets were assembled with Ru particles, followed by pyrolysis. • The fabricated electrode acts as a novel trifunctional catalyst for ORR, OER, and HER in alkaline solution. • The assembled catalyst showed superior open-circuit potential, peak power density, and stability. • Good catalytic activity are primarily attributed to distinct morphology, sufficient graphitization degree, and synergistic effects. [ABSTRACT FROM AUTHOR]

The expensiveness of oxygen reduction reaction (ORR) catalyst materials especially Pt has hindered the commercialization of next-generation energy conversion devices including metal–air batteries and polymer electrolyte membrane fuel cells. Fe– N –C has drawn attention as a nonprecious metal catalyst owing to its high but commercially unsatisfactory ORR performance; nevertheless, additional heteroatom co-doping could help augment its ORR activity. Here we report nitrogen/fluorine-coordinated iron-co-doped carbon (Fe@NFC) catalysts with improved ORR performance in alkaline media. The annealing temperature affects the nitrogen/fluorine doping and functional group formation, as ascertained by an analysis of control samples annealed at various temperatures. To assess the synergy between the doped fluorine and nitrogen-coordinated iron, we compare the catalyst annealed at 700 °C (Fe@NFC700) with control samples containing different heteroatom dopants but annealed at 700 °C (Fe@NC, Fe@FC). Fe@NFC700 shows improved ORR kinetics and onset potential than those of Fe@NC and commercial Pt/C, respectively, in alkaline media. • The most optimal annealing temperature of the Fe@NFC is found at 700 °C for the ORR. • F-doping increases the ORR favorable N -functional group ratio like Fe-N x. • The high ECSA from N -functional groups enhances the ORR performance. • F-functional groups like semi-ionic C –F bonds provide remarkable ORR kinetics. • The Fe@NFC700 catalyst exhibits higher onset potential than Pt/C in 0.1 M KOH. [ABSTRACT FROM AUTHOR]

Local geometric strain engineering is useful for modulating the performance of nitrogen‐coordinated transition metal‐carbon catalysts. However, realizing the nano‐level strain is technically challenging. Additionally, the structure‐property relationship between strain degree and performance remains poorly understood. Herein, it is conceptually predict that geometric bending induces more electron transfer from Zn to the coordinated N in Zn─N─C, leading to a positive shift of the d‐band center of the Zn atom, which promotes the adsorption reduction process of the O2 molecule and thus increases the intrinsic oxygen reduction reaction (ORR) activity. Moreover, a low‐temperature non‐saturated coordination strategy is proposed to prepare spherical porous carbon catalysts with surface‐enriched geometrically bent (20‐50°) Zn─N─C sites. Benefiting from the highly active Zn─N─C sites, large specific surface area and abundant pore structure, the optimized catalyst (S─Zn─N─C‐950) exhibited excellent intrinsic alkaline ORR activity (half‐wave potential E1/2 = 0.89 V) and high zinc‐air battery performance (peak power density of 229.2 mW cm−2), exceeding that of commercial Pt/C catalysts. Density functional theory (DFT) calculations show that when the geometrical bending angle is 30–45°, Zn centers with suitable charge transfer to the surrounding N can produce a moderate adsorption strength to the oxygen intermediate state, resulting in optimal ORR activity. [ABSTRACT FROM AUTHOR]

A novel strategy to prepare COF-derived carbon materials mediated by volatile guest molecule for efficient electrocatalytic oxygen reduction reaction is reported. [Display omitted] Covalent organic framework (COF) derived metal-free carbon materials have emerged as promising electrocatalysts for the oxygen reduction reaction (ORR). Herein, a volatile guest molecule mediated-pyrolysis strategy was explored on a designed thiophene-rich and imine-linked COF. Through the modulation of guest mediators (iodine and sulfur), the properties of the as-obtained carbon materials can be well regulated. The optimized nitrogen and sulfur dual-doped carbon electrocatalyst demonstrates remarkable ORR activity with a half-wave potential of 0.87 V and impressive durability, with only an 8% current loss over 21 h. The corresponding assembled zinc-air battery has a comparable power density (60 mW cm−2) to that of the commercial Pt/C. It is proposed that the coexistence of the guest mediators iodine and sulfur in the channels of COFs could prevent the loss of N species. The enhanced N content and N/S ratio are assumed to be responsible for the ORR performance. This study puts forward a novel strategy to prepare COF-derived carbon materials mediated by volatile guest molecules, which may provide new insights into the development of metal-free ORR catalysts. [ABSTRACT FROM AUTHOR]

Electrocatalysts with atomically dispersed metal sites (e.g. metal‐nitrogen‐carbon) have been deemed as promising alternatives for noble‐metal catalysts in couples of electrocatalytic reactions. However, the modulation of such atomic sites and the understanding of their interactions are still highly challenging. Herein, we propose a unique supermolecule assembly‐profile coating strategy to prepare a series of diatomic electrocatalysts by profile coating of eight Prussian blue analogues (PBAs) on supramolecular supports respectively as bimetallic sources. The detailed microstructure analysis revealed that the metal‐nitrogen‐carbon sites with four‐ (Zn−N4) and five‐coordination (Fe−N5) via the nitrogen coordination are similar to the cytochrome c oxidases. For promising electrocatalysis, such unique microstructure is able to activate oxygen molecules due to nitrogen‐bonding coordination with bimetal sites, thus leading to efficient four‐electron oxygen reduction in alkaline, neutral, and acid electrolytes. Especially, zinc group elements (e.g. Zn and Cd) with d10 electron configuration would significantly boost the nitrogen‐bonding coordination with bimetal sites to enhance electrocatalytic activity. The proof‐of‐concept for the general synthesis of advanced electrocatalysts with controllable bimetal active sites and the mechanistic understanding will promote the promising electrocatalysis by applying the similar principles. [ABSTRACT FROM AUTHOR]

Electrocatalysts with atomically dispersed metal sites (e.g. metal‐nitrogen‐carbon) have been deemed as promising alternatives for noble‐metal catalysts in couples of electrocatalytic reactions. However, the modulation of such atomic sites and the understanding of their interactions are still highly challenging. Herein, we propose a unique supermolecule assembly‐profile coating strategy to prepare a series of diatomic electrocatalysts by profile coating of eight Prussian blue analogues (PBAs) on supramolecular supports respectively as bimetallic sources. The detailed microstructure analysis revealed that the metal‐nitrogen‐carbon sites with four‐ (Zn−N4) and five‐coordination (Fe−N5) via the nitrogen coordination are similar to the cytochrome c oxidases. For promising electrocatalysis, such unique microstructure is able to activate oxygen molecules due to nitrogen‐bonding coordination with bimetal sites, thus leading to efficient four‐electron oxygen reduction in alkaline, neutral, and acid electrolytes. Especially, zinc group elements (e.g. Zn and Cd) with d10 electron configuration would significantly boost the nitrogen‐bonding coordination with bimetal sites to enhance electrocatalytic activity. The proof‐of‐concept for the general synthesis of advanced electrocatalysts with controllable bimetal active sites and the mechanistic understanding will promote the promising electrocatalysis by applying the similar principles. [ABSTRACT FROM AUTHOR]

The development of precious metal-free (M-N-C) catalysts for the oxygen reduction reaction (ORR) is considered crucial for reducing fuel cell costs. Herein, Co-Zn/NC interconnected frameworks with uniformly dispersed Co nanoparticles and graphitic carbon are designed and successfully synthesized through the in situ growth of zeolitic imidazolate frameworks (ZIF67 and ZIF8) along with biomass nano-microfibrillar cellulose (MFC), followed by pyrolysis. A Co-Zn/NC composite is prepared by combining Co-Zn/NC with a perfluorosulfonic acid polymer. The Co-Zn/NC composite catalyst exhibits excellent ORR catalytic activity (E0 = 0.974 V vs. RHE, E1/2 = 0.858 V vs. RHE) and good long-term durability, with 90% current retention after 10000s, surpassing that of commercial Pt/C in alkaline media. The hierarchical porous structure, coupled with the uniform distribution of Co nanoparticles and nitrogen doping, contributes to superior electrocatalytic performance, while the interconnected frameworks and graphitic carbon ensure good stability. Additionally, the Co-Zn/NC composite demonstrates promising applications in acidic media. This strategy offers significant guidance to develop advanced non-precious metal carbon-based catalysts for highly efficient and stable ORR. [ABSTRACT FROM AUTHOR]

The innovation of catalyst material for oxygen reduction reaction with a combination of metal precursors had been successfully synthesized using a variety of templates and post-treatment. The combination of two metal precursors consisting of transition metals (such as Fe, Ni, and Co) with the same metal ratio of 1:1 may affect the catalytic activity and physical properties. This research used 2,6-diaminopyridine as nitrogen-containing carbon material acting as a nitrogen and carbon source. This study used two types of hard templates which were LUDOX HS-40 colloidal silica and Montmorillonite K10 (MMT-K10) to optimize a dual metal with a porous nitrogen-doped catalyst. In addition, this research used a pyrolysis process at a temperature of 800 °C for 2 h within a nitrogen atmosphere. After that, post-treatment was carried out by leaching acid using a 0.5 M H2SO4 solution for 2 h. As a result, LUDOX HS-40 template has provided an advantage in increasing the oxygen reduction reaction (ORR) activity. In addition, the FeNi/CN-L catalyst yielded the highest catalytic activity with an electron transfer number of 3.61. LUDOX HS-40 template will make the shape of the FeNi/CN-L catalyst particles become irregular which in turn will increase ORR activity. This phenomenon is due to the electrostatic force from carbon to metal ions in which metal interactions with carbon particles occur. Thus, it can increase catalytic activity during the oxygen reduction reaction. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) supported zinc, cobalt, nitrogen, sulfur-doped porous carbon (CNT@ZnCo/NSC) catalysts are prepared by in situ growth of sulfur-containing bimetal zeolitic imidazolate framework (S–ZnCo-ZIF) polyhedrons on CNT with subsequent heat treatment. The microstructure, morphology, particle size distribution, specific surface area, and pore-size distribution of the catalysts are characterized by multiple techniques. CNT@ZnCo/NSC exhibits excellent catalytic activity for oxygen reduction reaction (ORR) with onset potential of 0.98 V and half-wave potential of 0.83 V, respectively, which are close to those of Pt/C. The addition of CNT inhibits the agglomeration and improves the conductivity of the catalysts, while S doping enhances the electrochemical surface area and introduces active sites. The special structure makes CNT@ZnCo/NSC possess proper specific surface area (390.8 m2 g−1) and large average pore size (5.26 nm). CNT@ZnCo/NSC contains more graphite-N (21%) and pyridine-N (55.9%) than CNT@ZnCo/NC (20%, 46.5%) and ZnCo/NC (8.2%, 45.8%). CNT@ZnCo/NSC catalyst has better methanol tolerance and long-term stability than commercial Pt/C. [Display omitted] • CNT supported Zn, Co, N, S-doped carbon are prepared by heating of S–ZnCo-ZIF/CNT. • CNT inhibits the agglomeration and improves the conductivity of CNT@ZnCo/NSC. • S doping enhances the ECSA of CNT@ZnCo/NSC and introduces active sites. • CNT@ZnCo/NSC exhibits excellent catalytic activity for ORR. [ABSTRACT FROM AUTHOR]

The supported nano-catalysts represented by platinum-carbon (Pt/C) are widely used with many advantages such as high surface area, high activity and cost-effective. Pt/C is one of the most important catalysts in modern industry and plays an indispensable role as the cathode for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFC) applications. However, due to the scarcity of noble metal, the large-scale preparation of novel Pt/C catalysts with higher catalytic activity has become a hot topic of research in both academia and industry. In this study, we develop an Fe3+ triggered micellization process to successfully obtain novel surface-engineered Pt/C catalyst with better oxygen reduction performance for fuel cell applications. This method has been scaled up and verified through pilot experiments, producing more than one kilogram of catalysts per batch with promising commercial values. This work will provide new ideas for the synthesis-route design and practical production of advanced nano-catalysts. [Display omitted] • An Fe3+ triggered micellization method is investigated to synthesize surface-engineered Pt/C catalyst. • The water-based synthesis method is facile to scale-up with a kilogram scale verification. • The simultaneous nitrogen doping during the synthesis process further promotes the oxygen reduction performance. • The surface-engineered Pt/C sample shows a superior performance than commercial Pt/C for oxygen reduction reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] Oxygen reduction reaction (ORR) is an essential half-reaction in next-generation energy storage and conversion systems, such as metal-air batteries and fuel cells. However, its practical application is restricted by the slow intrinsic kinetics, and the high price and low storage of noble metal electrocatalysts. Herein, unique CoFe nanoparticles encapsulated in N -doped carbon (CoFe-NC-Z8-900) with high content graphite-N derived from CoFe-g-C 3 N 4 @ZIF-8 via stepwise pyrolysis is reported as effective ORR catalysts. The increase of graphitic nitrogen content can enhance both the electrical conductivity and the adsorption of oxygen-containing intermediates, resulting in improved catalytic performance. Fortunately, CoFe-NC-Z8-900 exhibits an exceptionally high half-wave potential (E 1/2) of 0.914 V in a 0.1 M KOH solution. The excellent ORR electrocatalytic activity can be mainly attributed to the synergistic effect of the CoFe bimetal and the relatively high content of graphite-N. This study offers a unique method for creating powerful nitrogen-doped carbon coated metal nanoparticle electrocatalysts. [ABSTRACT FROM AUTHOR]

Fe‐N/C catalysts have currently comparable oxygen reduction reaction (ORR) activity to Pt/C catalysts, which are up for consideration as the most promising non‐precious metal material for research. In spite of this, its development and application are limited by the Fenton effect and insufficient stability. Herein, we have fabricated a FeNi‐nitrogen‐doped porous carbon (FeNi‐NPC) catalyst using solvent thermal method, made from the bimetallic (Fe, Ni)‐doped ZIF‐8. A soft template of glucose was used to control the pore structure and active specific surface area of the catalyst. With the benefit of the electronic effect of the bimetal, FeNi‐NPC catalysts exhibit superior ORR activity and stability to Pt/C catalysts in both acidic (E1/2=0.8672 V) and alkaline (E1/2=0.8663 V) conditions. FeNi‐NPC demonstrated peak power densities in proton exchange membrane fuel cells (PEMFC) of up to 865 mW cm−2, which exceeds the currently reported M‐N/C catalysts. The work presented here will lead to the design of efficient ORR electrocatalysts in PEMFC devices. [ABSTRACT FROM AUTHOR]

We report here the synthesis of N-doped porous carbon (PC) through a convenient melamine pre-grafting strategy. The melamine derivative with a monolayer structure was first grafted on the surface of the micropores of PC using a suitable diazotization reaction of melamine in an aqueous solution. After pyrolysis, PC grafting with melamine derivative was converted to the obtained N-doped PC. Meanwhile, more nitrogen dopants were grafted, and nitrogen functionalities were reconstructed to generate more graphitic N and pyridinic N atoms, in which the mesopores volume was consequently enlarged. Because of the unique structures mentioned above, the as-obtained N-doped PC exhibited enhanced oxygen reduction activity under alkaline compared with the N-doped PC from the standard physical mixture of PC and melamine. Besides, the obtained N-doped PC showed a comparable half-wave potential, remarkable durability, and good methanol tolerance compared with the commercial 20% Pt/C electrocatalyst. The results presented here could guide the development of new and improving metal-free nitrogen-doped porous carbon catalysts toward oxygen reduction reaction. • Melamine pre-grafting strategy boosts N dopants and optimizes pores for ORR. • Reconstruction enables more pyridinic and graphitic N dopants in PC. • Metal-free N-rich porous carbon has excellent ORR performance. [ABSTRACT FROM AUTHOR]

The cost-effective and green preparation of electrocatalysts that are highly effective for both the cathode (reduction of oxygen) and anode (methanal oxidation) reactions is crucial for boosting the development of Direct Methanol fuel cells (DMFCs). This article describes a novel designed nitrogen and phosphorous co-doped honeycomb-like electrocatalyst (CAMN6P-3), which is derived from a hydrogel network formed with silk protein, polyaniline, and polyacrylamide. Notably, the CAMN6P-3 material has a surprisingly high nitrogen content (6.82%) and a high specific surface area (2494.55 m2 g−1). A high onset potential (1.11 V) was observed for the CAMN6P-3 catalyst, as well as a high limiting current density (5.4 mA.cm−2) during ORR. Furthermore, Pt/CAMN6P-3 demonstrates considerable catalytic activity as well as electrochemical stability for MOR as a catalyst carrier for Pt nanoparticles (Pt NPs). After long-term stability tests, the current density in the MOR was equivalent to a factor of twenty times that of the catalyst made from Pt/C. This superior performance can be attributed to the special nanostructure, where the honeycomb nanostructure not only provides an efficient channel for electron transfer and exposes more active sites, but also facilitates a high degree of dispersion of the Pt nanoparticles. From the perspective of sustainable development, combined with low-cost materials and the green preparation process, this work has a certain reference value for the development of highly efficient catalysts in the field of clean fuel cells. [ABSTRACT FROM AUTHOR]

[Display omitted] In this study, we present a bimetallic ion coexistence encapsulation strategy employing hexadecyl trimethyl ammonium bromide (CTAB) as a mediator to anchor cobalt–nickel (CoNi) bimetals in nitrogen-doped porous carbon cubic nanoboxes (CoNi@NC). The fully encapsulated and uniformly dispersed CoNi nanoparticles with the improved density of active sites help to accelerate the oxygen reduction reaction (ORR) kinetics and provide an efficient charge/mass transport environment. Zinc-air battery (ZAB) equipped CoNi@NC as cathode exhibits an open-circuit voltage of 1.45 V, a specific capacity of 870.0 mAh g−1, and a power density of 168.8 mW cm−2. Moreover, the two CoNi@NC-based ZABs in series display a stable discharge specific capacity of 783.0 mAh g−1, as well as a large peak power density of 387.9 mW cm−2. This work provides an effective way to tune the dispersion of nanoparticles to boost active sites in nitrogen-doped carbon structure, and enhance the ORR activity of bimetallic catalysts. [ABSTRACT FROM AUTHOR]

The atom‐cluster interaction has recently been exploited as an effective way to increase the performance of metal‐nitrogen‐carbon catalysts for oxygen reduction reaction (ORR). However, the rational design of such catalysts and understanding their structure‐property correlations remain a great challenge. Herein, we demonstrate that the introduction of adjacent metal (M)−N4 single atoms (SAs) could significantly improve the ORR performance of a well‐screened Fe atomic cluster (AC) catalyst by combining density functional theory (DFT) calculations and experimental analysis. The DFT studies suggest that the Cu−N4 SAs act as a modulator to assist the O2 adsorption and cleavage of O−O bond on the Fe AC active center, as well as optimize the release of OH* intermediates to accelerate the whole ORR kinetic. The depositing of Fe AC with Cu−N4 SAs on nitrogen doped mesoporous carbon nanosheet are then constructed through a universal interfacial monomicelles assembly strategy. Consistent with theoretical predictions, the resultant catalyst exhibits an outstanding ORR performance with a half‐wave potential of 0.92 eV in alkali and 0.80 eV in acid, as well as a high power density of 214.8 mW cm−2 in zinc air battery. This work provides a novel strategy for precisely tuning the atomically dispersed poly‐metallic centers for electrocatalysis. [ABSTRACT FROM AUTHOR]

The atom‐cluster interaction has recently been exploited as an effective way to increase the performance of metal‐nitrogen‐carbon catalysts for oxygen reduction reaction (ORR). However, the rational design of such catalysts and understanding their structure‐property correlations remain a great challenge. Herein, we demonstrate that the introduction of adjacent metal (M)−N4 single atoms (SAs) could significantly improve the ORR performance of a well‐screened Fe atomic cluster (AC) catalyst by combining density functional theory (DFT) calculations and experimental analysis. The DFT studies suggest that the Cu−N4 SAs act as a modulator to assist the O2 adsorption and cleavage of O−O bond on the Fe AC active center, as well as optimize the release of OH* intermediates to accelerate the whole ORR kinetic. The depositing of Fe AC with Cu−N4 SAs on nitrogen doped mesoporous carbon nanosheet are then constructed through a universal interfacial monomicelles assembly strategy. Consistent with theoretical predictions, the resultant catalyst exhibits an outstanding ORR performance with a half‐wave potential of 0.92 eV in alkali and 0.80 eV in acid, as well as a high power density of 214.8 mW cm−2 in zinc air battery. This work provides a novel strategy for precisely tuning the atomically dispersed poly‐metallic centers for electrocatalysis. [ABSTRACT FROM AUTHOR]

N -doped porous carbon monatomic iron catalysts (Fe SA /NPCs) obtained by polydopamine modification strategy were used for high efficiency oxygen reduction reactions and zinc-air batteries. [Display omitted] • Nitrogen doped porous carbon materials (NPCs) were prepared based on ZIF-L. • Stable hollow leaf-like morphology was maintained by coating PDA and nitrogen content was adjusted. • Fe SA was easily anchored on NPCs with luxuriant anchoring sites. • Fe SA /NPCs shows excellent electrochemical performance in oxygen reduction and zinc air batteries. Metal-nitrogen-carbon (M N C) catalysts, especially Fe N C catalysts, are considered promising candidates to replace Pt-based catalysts, but Fe N C catalysts still present certain challenges in controlled-synthesis and energy device applications. In this paper, through the modification strategy of poly-dopamine (PDA) to maintain 2D leaf morphology to obtain more active sites and further adjust the N content, N -doped porous carbon monatomic iron catalyst (Fe SA /NPCs) with rich-nitrogen content was prepared. XPS analysis showed that compared with C-ZIF-Fe, the contents of graphite nitrogen and pyridine nitrogen increased in Fe SA /NPCs. The hollow structure with defects and Fe-N 4 configuration of Fe single atom show more active sites for the catalyst, and positively promote the diffusion of reactants, oxygen exchange and electron transport, thus changing the reaction kinetics and promoting the improvement of ORR activity. Fe SA /NPCs electrocatalyst exhibits good half-wave potential and onset potential at low loading (E 1/2 = 0.93 V, E onset = 1.0 V). In addition, the methanol tolerance, stability and Tafel slope are better than those of commercial Pt/C. Excitingly, the zinc-air cell with Fe SA /NPCs as cathode material achieves a power density of 223 mW cm−2 and exhibits a long-term stability higher than 200 h. This work shows that nitrogen-doped porous carbon materials as well as iron monoatoms play important roles in improving electrocatalytic performance. [ABSTRACT FROM AUTHOR]

The search of active, stable and low costs catalysts for the oxygen reduction reaction (ORR) is crucial for the extensive use of fuel cells and metal–air batteries. The development of metal-free catalysts, instead of platinum-based materials, can dramatically reduce the cost and increase the efficiency of these devices. In this work, carbon nanohorns (CNHs) have been covalently functionalized with N-containing heterocycles by the Tour reaction protocol and tested as metal-free ORR catalysts. The insertion of N-functionalities favored the complete reduction of oxygen to hydroxyl ions, while their absence favored the production of hydrogen peroxide. With the aim of determining the N-species responsible for the ORR activity of CNHs, photoemission and electrochemical measurements were combined. Results suggest that protonated N is the main species involved in the ORR process, facilitating the adsorption of oxygen, with their consequent reduction to neutral hydrogenated N species. [ABSTRACT FROM AUTHOR]

The anion‐exchange membrane direct ammonia fuel cell, as a carbon‐free fuel cell type, has recently received increasing attention albeit suffering from high cost of using the platinum‐group metal oxygen reduction reaction (ORR) catalysts. To pave the development of this promising power source, the atomically dispersed transition metal‐nitrogen‐carbon (M‐N‐C) materials with low cost and high ORR performance have allured to investigate their ammonia tolerance during the ORR. Herein, it is initially deconvoluted how compositional and structural elements of FeN4 sites modulate catalyst's performance. Furthermore, ORR catalytic activities of the M‐N‐C (M = Fe, Co or Mn) and Pt/C catalysts are investigated in ammonia‐containing electrolytes, showing that M‐N‐C catalysts have better ammonia tolerance than Pt/C. Among others, the Fe‐N‐C exhibits the best ammonia tolerance with only 4 mV negative shifts of half‐wave potential, 2.7% decrease of current, and negligibly irreversible activity loss. The superior ammonia tolerance of MN4 sites to Pt (111) surface is further confirmed by density functional theory calculations. The adsorption capacity of MN4 for O2 is higher than NH3 and the bonding force between MN4 and O2 is stronger than NH3, whereas opposite adsorption capacity and bonding force trends are observed on Pt (111) surface. [ABSTRACT FROM AUTHOR]

Fe/Co/N co-doped multi-channel interpenetrating three-dimensional graphene catalyst (FeCo–N-3D-HG) with good oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic performances is prepared by a facile method, using poly (2,5-benzimidazole) (ABPBI), iron salt, cobalt salt and nanometer CaCO 3 (template). ABPBI forms a complex with iron and cobalt ions and the complex is coated on the surface of CaCO 3. The pyrolysis process is carried out in an Ar gas protection, the template is removed by acid to obtain FeCo–N-3D-HG. The results show that FeCo–N-3D-HG is three-dimensional multi-layered graphene structure with multi-channels. The catalytic performance of ORR (E 1/2 = 0.860 V vs RHE) is better than 20 wt% Pt/C in O 2 saturated 0.1 M KOH electrolyte. The catalyst also shows similar OER performance with the RuO 2 in 1 M KOH solution. The prepared zinc-air battery exhibits outstanding peak power density (261.7 mW cm−2), preeminent specific capacity (760.1 mAh g−1), and good cycle durability (150 h). High nitrogen-containing Fe/Co/N co-doped three-dimensional graphene bifunctional oxygen catalysts is prepared by one-step pyrolysis for zinc air battery. The bimetallic synergistic effect, three-dimensional porous structure of graphene and the high nitrogen content greatly improve the catalytic performance. [Display omitted] • FeCo–N-3D-HG with multistage perforated is prepared by nano CaCO 3. • High N, Fe and Co content is achieved by complex of ABPBI with Fe3+ and Co3+. • The synergistic effect of FeCo–N-3D-HG can enhance the catalytic performance. • The zinc air battery with this catalyst shows high power density and durability. [ABSTRACT FROM AUTHOR]

An efficient and low-cost oxygen catalyst for the oxygen reduction reaction (ORR) was developed by in situ growth of Mn-Mo oxide nanoparticles on nitrogen-doped carbon nanotubes (NCNTs). Doped nitrogen effectively increases the electron conductivity of the MnMoO4@NCNT complex and the binding energy between the Mn-Mo oxide nanoparticles and carbon nanotubes (CNTs), leading to fast charge transfer and more catalytically active sites. Combining Mn and Mo with NCNTs improves the catalytic activity and promotes both electron and mass transfers, greatly enhancing the catalytic ability for ORR. As a result, MnMoO4@NCNT exhibited a comparable half-wave potential to commercial Pt/C and superior durability, demonstrating great potential for application in renewable energy conversion systems. [ABSTRACT FROM AUTHOR]

Nitrogen‐doped carbon is considered one of the most promising oxygen reduction catalysts due to its low cost and high activity, however, it still falls short of Pt/C. In this study, we report a strategy for the preparation of highly reactive N‐doped hierarchical porous carbon by primary pyrolysis using zinc acetate as a stand‐alone zinc source and amino‐rich reactants as carbon and nitrogen sources to introduce Zn‐Nx structures into mesoporous structures generated by the hard template method using the strong coordination of zinc and amino groups. Benefited from the simultaneous optimization of the hierarchical porous structure and nitrogen‐doping, the half‐wave potential of Zn(OAc)2–DCD/HPC is as high as 0.909 V vs. RHE, much better than that of commercial Pt/C catalysts (0.872 V vs. RHE). In addition, zinc‐air batteries assembled with Zn(OAc)2–DCD/HPC (Pmax=198 mW cm−2) as the cathode exhibit higher peak power density compared to Pt/C (Pmax=168 mW cm−2). This strategy might open up new opportunities for designing and developing highly active metal‐free catalysts. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWCNTs) with one-dimensional nanostructure are an ideal support for oxygen reduction reaction (ORR) catalysts thanks to their intrinsic outstanding electrical conductivity and high specific surface area. Iron and nitrogen doping could alter the local electronic structure and therefore enhance the ORR activity of MWCNTs, but the preparation process always includes complicated growth conditions and post-treatment. Herein, an iron and nitrogen co-modified multi-walled carbon nanotubes (Fe–N-MWCNTs) with hierarchical nanostructure is engineered and synthesized via a simple two-step pyrolysis approach. Large specific surface area, low resistivity, and intensified charge density near the Fermi level synergistically endow the Fe–N-MWCNTs with outstanding ORR activity. The optimal Fe–N-MWCNTs exhibit a higher onset potential value of 0.92 V (versus RHE) and half-wave potential (E 1/2) of 0.85 V (versus RHE) in 0.1 M KOH medium, which exceeds the benchmark Pt/C electrocatalyst (E 1/2 = 0.84 V). This strategy of modifying MWCNTs support by a simple calcination process provides a feasible method to prepare cost-efficient ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

Innovations in energy storage and conversion technologies are closely dependent on developing superior materials that can be used in this field. Here, we present an industrially scalable and low-cost solvothermal method for synthesizing Si-N-co-doped (Si-N-GN) and N-doped graphene (N-GN) with a high specific surface area of 523 m2 g−1 and 1289 m2 g−1, respectively. Silicon atoms were successfully incorporated into the 2D graphene at a doping rate of 2.28 at.% via Si-C, Si-N, and Si-O bonds, thanks to the decarbonylation of N,N-dimethyl formamide (DMF) into dimethylamine and highly reactive carbonyl at the solvothermal conditions. The Si-N-GN exhibited an average electron transfer number of 3.83 e− per mole of O 2 in a wide potential range with similar on-set potential (0.988 V vs. 1.012 V), greater methanol tolerance capability, and higher diffusion limiting current density (7.2 vs. 6.5 mA cm−2 at 0.4 V) for oxygen reduction reaction (ORR) in alkaline electrolytes compared to the commercial Pt/C catalyst. The improved ORR performance of Si-N-GN was attributed to the effectively decreased adsorption energy of O 2 on SiC 4 and SiN 1 C 3 type bondings supported by the density functional theory (DFT) calculations based on the model created according to the XPS results. The promising electrocatalytic activity of Si-N-GN for ORR could also be enlarged to other electrochemical applications, including metal-air batteries. [Display omitted] • Nitrogen-doped and silicon-nitrogen co-doped graphene can be produced by a scalable procedure. • SiC 4 and SiN 1 C 3, as new active centers on graphene, promote the ORR activity close to Pt/C. • Silicon-nitrogen co-doped graphene is a promising candidate material for electrochemical technologies. [ABSTRACT FROM AUTHOR]

Electrocatalytic oxygen reduction reaction (ORR) has been intensively studied for environmentally benign applications. However, insufficient understanding of ORR 2 e−‐pathway mechanism at the atomic level inhibits rational design of catalysts with both high activity and selectivity, causing concerns including catalyst degradation due to Fenton reaction or poor efficiency of H2O2 electrosynthesis. Herein we show that the generally accepted ORR electrocatalyst design based on a Sabatier volcano plot argument optimises activity but is unable to account for the 2 e−‐pathway selectivity. Through electrochemical and operando spectroscopic studies on a series of CoNx/carbon nanotube hybrids, a construction‐driven approach based on an extended "dynamic active site saturation" model that aims to create the maximum number of 2 e− ORR sites by directing the secondary ORR electron transfer towards the 2 e− intermediate is proven to be attainable by manipulating O2 hydrogenation kinetics. [ABSTRACT FROM AUTHOR]

Electrocatalytic oxygen reduction reaction (ORR) has been intensively studied for environmentally benign applications. However, insufficient understanding of ORR 2 e−‐pathway mechanism at the atomic level inhibits rational design of catalysts with both high activity and selectivity, causing concerns including catalyst degradation due to Fenton reaction or poor efficiency of H2O2 electrosynthesis. Herein we show that the generally accepted ORR electrocatalyst design based on a Sabatier volcano plot argument optimises activity but is unable to account for the 2 e−‐pathway selectivity. Through electrochemical and operando spectroscopic studies on a series of CoNx/carbon nanotube hybrids, a construction‐driven approach based on an extended "dynamic active site saturation" model that aims to create the maximum number of 2 e− ORR sites by directing the secondary ORR electron transfer towards the 2 e− intermediate is proven to be attainable by manipulating O2 hydrogenation kinetics. [ABSTRACT FROM AUTHOR]

Atomically dispersed 3D transitional metal active sites with nitrogen coordination anchored on carbon support have emerged as a kind of promising electrocatalyst toward oxygen reduction reaction (ORR) in the field of fuel cells and metal–air cells. However, it is still a challenge to accurately modulate the coordination structure of single‐atom metal sites, especially first‐shell coordination, as well as identify the relationship between the geometric/electronic structure and ORR performance. Herein, a carbon‐supported single‐atom nickel catalyst is fabricated with boron and nitrogen dual coordination (denoted as Ni‐B/N‐C). The hard X‐ray absorption spectrum result reveals that atomically dispersed Ni active sites are coordinated with one B atom and three N atoms in the first shell (denoted as Ni‐B1N3). The Ni‐B/N‐C catalyst exhibits a half‐wave potential (E1/2) of 0.87 V versus RHE, along with a distinguished long‐term durability in alkaline media, which is superior to commercial Pt/C. Density functional theory calculations indicate that the Ni‐B1N3 active sites are more favorable for the adsorption of ORR intermediates relative to Ni‐N4, leading to the reduction of thermodynamic barrier and the acceleration of reaction kinetics, which accounts for the increased intrinsic activity. [ABSTRACT FROM AUTHOR]

Metal/nitrogen-doped carbon single-atom catalysts (M−N−C SACs) show excellent catalytic performance with a maximum atom utilization and customizable tunable electronic structure. However, precisely modulating the M−Nx coordination in M−N−C SACs remains a grand challenge. Here, we used a N-rich nucleobase coordination self-assembly strategy to precisely regulate the dispersion of metal atoms by controlling the metal ratio. Meanwhile, the elimination of Zn during pyrolysis produced porous carbon microspheres with a specific surface area of up to 1151 m2 g−1, allowing maximum exposure of Co−N4 sites and facilitating charge transport in the oxygen reduction reaction (ORR) process. Thereby, the monodispersed cobalt sites (Co−N4) in N-rich (18.49 at%) porous carbon microspheres (CoSA/N−PCMS) displayed excellent ORR activity under alkaline conditions. Simultaneously, the Zn−air battery (ZAB) assembled with CoSA/N−PCMS outperformed Pt/C+RuO2-based ZABs in terms of power density and capacity, proving that they have good prospects for practical application. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene is currently recognized as one of the most promising catalysts for the oxygen reduction reaction (ORR). It has been demonstrated to act as a metal-free electrode with good electrocatalytic activity and long-term operation stability, excellent for the ORR in proton exchange membrane fuel cells (PEMFCs). As a consequence, intensive research has been dedicated to the investigation of this catalyst through varying the methodologies for the synthesis, characterization, and technologies improvement. A simple, scalable, single-step synthesis method for nitrogen-doped graphene oxide preparation was adopted in this paper. The physical and chemical properties of various materials obtained from different precursors have been evaluated and compared, leading to the conclusion that ammonia allows for a higher resulting nitrogen concentration, due to its high vapor pressure, which facilitates the functionalization reaction of graphene oxide. Electrochemical measurements indicated that the presence of nitrogen-doped oxide can effectively enhance the electrocatalytic activity and stability for ORR, making it a viable candidate for practical application as a PEMFC cathode electrode. [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]

The oxygen electroreduction mechanism on the V‐ and Nb‐doped nitrogen‐codoped (6,6)armchair carbon nanotube with incorporated MN4 fragment has been studied using the ωB97XD and PBE density functional theory approaches. The metal center in MN4 fragment and the adjacent NCCN double bond (C2 site) of the support have been revealed as active centers. The metal active centers turned out to be irreversibly oxidized at the first step of ORR affording stable O*, 2O*, or O*HO* adsorbates depending on the applied electrode potential U, that makes them no longer active in ORR. Therefore, the C2 site comes at the forefront in ORR catalysis. Among the metal oxidized forms M(O)N4, M(O)(O)N4, and M(O)(OH)N4CNT, the C2 site of the latter turned out to be most active for 4e dissociative ORR. For both metals the last protonation/electron transfer step, HO* + H* → H2O, is the rate‐limiting step. The alternative hydrogen peroxide formation is not only thermodynamically less favorable but also kinetically slower than the 4e dissociative ORR route on the C2 site of model M(O)(OH)N4CNT catalyst. [ABSTRACT FROM AUTHOR]

The emerging star of single atomic site (SAS) catalyst has been regarded as the most promising Pt‐substituted electrocatalyst for oxygen reduction reaction (ORR) in anion‐exchange membrane fuel cells (AEMFCs). However, the metal loading in SAS directly affects the whole device performance. Herein, we report a dual nitrogen source coordinated strategy to realize high dense Cu−N4 SAS with a metal loading of 5.61 wt% supported on 3D N‐doped carbon nanotubes/graphene structure wherein simultaneously performs superior ORR activity and stability in alkaline media. When applied in H2/O2 AEMFC, it could reach an open‐circuit voltage of 0.90 V and a peak power density of 324 mW cm−2. Operando synchrotron radiation analyses identify the reconstruction from initial Cu−N4 to Cu−N4/Cu‐nanoclusters (NC) and the subsequent Cu−N3/Cu−NC under working conditions, which gradually regulate the d‐band center of central metal and balance the Gibbs free energy of *OOH and *O intermediates, benefiting to ORR activity. [ABSTRACT FROM AUTHOR]

The emerging star of single atomic site (SAS) catalyst has been regarded as the most promising Pt‐substituted electrocatalyst for oxygen reduction reaction (ORR) in anion‐exchange membrane fuel cells (AEMFCs). However, the metal loading in SAS directly affects the whole device performance. Herein, we report a dual nitrogen source coordinated strategy to realize high dense Cu−N4 SAS with a metal loading of 5.61 wt% supported on 3D N‐doped carbon nanotubes/graphene structure wherein simultaneously performs superior ORR activity and stability in alkaline media. When applied in H2/O2 AEMFC, it could reach an open‐circuit voltage of 0.90 V and a peak power density of 324 mW cm−2. Operando synchrotron radiation analyses identify the reconstruction from initial Cu−N4 to Cu−N4/Cu‐nanoclusters (NC) and the subsequent Cu−N3/Cu−NC under working conditions, which gradually regulate the d‐band center of central metal and balance the Gibbs free energy of *OOH and *O intermediates, benefiting to ORR activity. [ABSTRACT FROM AUTHOR]

One of the biggest challenges in producing fuel cells at affordable prices is to synthesize carbon materials selectively doped with graphitic nitrogen, as it is considered the most active nitrogen species for the oxygen reduction reaction (ORR). So far, all strategies focus on the use of nitrogen-containing carbon precursors, which limits the functionalization of commercially available carbon materials. Here, we present a post-functionalization method to boost the catalytic properties of carbon materials for the ORR by selectively enriching activated carbons with nitrogen graphitic species. A commercial high-surface area activated carbon was post-functionalized by a two-step procedure. First, the commercial carbon was mixed with different carbon/urea weight ratios and heated in air at 350 °C. Then, the functionalized materials were heat-treated at high temperature (from 700 to 1300 °C) to tailor the amount and distribution of the different nitrogen species in the resulting carbon structure. Nitrogen functionalization using a carbon to urea weight ratio of 1:2 and heat-treatment at 1100 °C led to highly selective doping in graphitic nitrogen species, which provided the tools to individually asses the catalytic activity of these nitrogen species. In addition, this study presents a low-cost and easily feasible synthesis route to improve the catalytic activity of carbon materials, leading to an onset potential of almost 0.9 V compared to reversible hydrogen electrode for ORR in an alkaline electrolyte. Moreover, this study provides significant evidence for the key role of graphitic nitrogen. [Display omitted] • An efficient and selective N-functionalization of activated carbons is presented. • This selective post-functionalization does not modify the textural properties. • Carbon materials selectively enriched with graphitic nitrogen were produced. • Graphitic nitrogen appears to be a highly active site for ORR. [ABSTRACT FROM AUTHOR]

Nitrogen‐doped carbons are among the fastest‐growing class of materials used for oxygen electrocatalysis, namely, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), thanks to their low cost, environmental friendliness, excellent electrical conductivity, and scalable synthesis. The perspective of replacing precious metal‐based electrocatalysts with nitrogen‐doped carbon is highly desirable for reducing costs in energy conversion and storage systems. In this review, the role of nitrogen and N‐induced structural defects on the enhanced performance of N‐doped carbon electrocatalysts toward the OER and the ORR as well as their applications for energy conversion and storage technologies is summarized. The synthesis of N‐doped carbon electrocatalysts and the characterization of their nitrogen functional groups and active sites for the conversion of oxygen are also reviewed. The electrocatalytic performance of the main types of N‐doped carbon materials for OER/ORR electrocatalysis are then discussed. Finally, major challenges and future opportunities of N‐doped carbons as advanced oxygen electrocatalysts are highlighted. [ABSTRACT FROM AUTHOR]

The development of electrocatalysts for oxygen reduction reaction (ORR) is important for energy conversion devices, such as fuel cells, and metal‐air batteries. Here, we have developed a confined space strategy to prepare a two‐dimensional (2D) leaf‐like nitrogen (N)‐containing porous carbon as a single‐atom catalyst substrate. ZIF−L materials have been confined in a thin silica layer to regulate the pyrolysis. The obtained Fe single atoms doped N‐containing porous carbons (Fe SAs/N−C) maintain the 2D morphology and have Fe single‐atom active sites. Correspondingly, Fe SAs/N−C exhibits excellent ORR performance (E1/2 of 0.907 V), which is more positive than those of commercially available Pt/C (0.874 V) and most reported non‐noble metal catalysts. The durability test shows that Fe SAs/N−C exhibits good stability during electrocatalytic process. This rational design shows a new strategy to prepare 2D catalyst supports with single‐atom active sites. [ABSTRACT FROM AUTHOR]

Cathodic oxygen reduction reaction is a decisive factor for fuel cell. In this work, for the first time, we demonstrated the synthesis of N -doped carbon hollow spheres derived from conjugated microporous polymers. The resulting sample remained the inherent porosity and N component with hollow spherical morphology, which exhibits excellent ORR performance with higher limiting current density and stability than that of commercial Pt/C catalyst in alkaline solution. [Display omitted] The exploitation non-precious or metal-free electrocatalysts of oxygen reduction reaction (ORR) is of significance for construction of next-generation fuel cells. In this work, hollow-spherical conjugated microporous polymers (CMPs) comprising porphyrin units were synthesized as precursors to prepare N -doping porous carbon spheres (CMP-NP-x) by a direct pyrolysis method. The as-resulted CMP-NP-x exhibited spherical morphology with hollow structure similar to that of CMPs precursors. The BET surface area of CMP-NP-x can be tailored by the pyrolysis temperature varying from 868 m2 g−1 to 1118 m2 g−1. According to XPS analysis, the pyrrolic N content in the sample decreased but the graphitic N and pyridinic N increased with increasing of the pyrolysis temperature from 800 °C to 1000 °C. Taking advantages of porous structure with large accessible surface areas and N species active sites, the resulting CMP-NP-x showed superior ORR activity and methanol tolerance to commercial Pt/C catalyst. In particular, CMP-NP-900 possesses the highest onset potential (0.930 V), half-wave potential (0.857 V) and limiting current density of 4.45 mA cm−2, compared with Pt/C catalyst and other samples, making it a promising metal-free catalyst superior to commercial Pt/C catalyst in alkalic condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe/N C exhibits enhanced selectivity for the 4-electron pathway in the ORR. • Co and CoFe/N C demonstrate higher catalytic activity, albeit with lower selectivity. • Co affects the distribution of nitrogenated species and nitrogen content. • CoFe/N C catalysts demonstrate superior catalytic activity for the ORR. Iron-based noble-metal-free electrocatalysts exhibit impressive performance and stability for the Oxygen reduction reaction (ORR) in alkaline media, but face challenges. This study investigates the impact of Co addition to Fe in nitrogen(N)-doped carbon (Fe/N C) catalysts prepared via one-pot synthesis involving direct pyrolysis of the metal (M) and 2,4,6-tris(2-pyridyl)-s-triazine complexes (M-TPTZ) on carbon. Comprehensive characterization reveals N -doped carbon structures with single-atom sites and metal oxides, with M-N x centers mainly in carbon pores and metal oxides on the carbon surface. N 2 adsorption/desorption experiments and electrochemical surface area (ECSA) reveals that Co introduction enhances the catalyst surface area. Moreover, Co addition alters nitrogenated species distribution, affecting catalytic activity. Electrochemical studies rank catalytic activity as Fe/N C < Co/N C < CoFe/N C, while rotating ring-disk electrode (RRDE) investigations show mixed 2 and 4 electrons pathways. Fe/N C follows a 4e- pathway with minimal HO 2 − production, while Co-containing catalysts suggest a mixed (2e- + 2e-) pathway with an average of 3.75 electrons involved. This divergence highlights nuanced electrochemical characteristics of Fe- and Co-based materials, emphasizing the need for in-depth characterization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Heteroatoms in graphene-based materials modulate their electrochemical activity. • Supporting Ni on S,N-doped graphene decreases the HO 2 − route for ORR below 10% • Supporting Ni on doped graphene materials reduces HER overpotential ca. 0.50 V. • These Ni materials are promising electrocatalysts for alkaline PEM devices. In this work, Ni nanoparticles (NPs), with nominal metallic loading of 20 wt%, were deposited on graphene-based materials (GMs) doped with nitrogen and sulphur, in order to study their electrocatalytic activity towards the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in alkaline medium. Different chemical reducing agents were employed to synthesize the catalysts. Results indicate that the presence of heteroatoms in the GMs influences the activity of both the GMs and the Ni-based catalysts. Thus, best results were obtained for catalyst containing nitrogen and sulphur for the ORR which favours the direct four-electron pathway, whereas for the HER, the highest performance was observed for N -doped materials. [ABSTRACT FROM AUTHOR]

Utilizing shrimp waste-derived Chitosan as biomass source, we developed metal-free nitrogen and sulfur-doped porous carbon (NSPC) with a high specific surface area of 609.53 m2/g as a remarkable electrocatalyst for oxygen reduction reaction (ORR), surpassing benchmark Pt/C with half-wave (0.8574 V) and onset (0.9573 V) potentials in alkaline (0.1 M KOH) media. Besides high electrocatalytic activity, NSPC-800 showed excellent methanol tolerance ability and significantly low hydrogen peroxide yields (H 2 O 2) of 5 % and 8 % in 0.1 M KOH and 0.5 M H 2 SO 4 , which is comparably lower than the previously reported chitosan based non-precious catalysts. Interestingly NSPC-800 displays robust stability in 0.1 M KOH electrolyte, improving the current retention rate from 89.17 % to 95.18 % over an increased operation period, evidencing its self-activating characteristics. This self-activating stability is also mirrored in 0.5 M H 2 SO 4 where both fresh and recycled (after 5000 CV cyles) NSPC-800 catalysts retained more than half of their initial current. Additionally, to identify the nature of the active sites, the ORR measurements were correlated with ex-situ spectroscopy for post-stability of fresh and recycled NSPC-800 catalysts revealed dynamic reconfiguration of nitrogen, sulfur, and oxygen active sites evidenced compared to the pre-stability elemental surface, indicating an adaptive response of the catalyst to the harsh operating environment. In the future, our biomass-derived NSPC-800 will pave the way to develop cost-effective and highly efficient catalysts from waste to energy devices promising a twin-goal approach, contributing to the circular economy and sustainable development goals. Schematic illustration of chitosan-derived nitrogen and sulfur-doped porous carbon (NSPC-800) and its application in fuel cells, associated contribution in sustainable development goals. [Display omitted] [ABSTRACT FROM AUTHOR]

Numerous active sites and hierarchical pore structures are important for improving catalytic performance for the oxygen reduction reaction (ORR). In this work, a series of iron-nitrogen-doped porous carbon materials (Fe– N –C) with ORR catalytic activity were prepared by a one-step pyrolysis method using enzymolytic lignin as the raw material, soy protein isolate and iron chloride as dopants. The results showed that the samples with the best performance have abundant Fe-Nx active sites and mesoporous structures. At the same time, the electrocatalytic results indicate that the half-wave potential of catalyst was 0.84 V, which reached 96.55% of commercial Pt/C catalysts (E 1/2 = 0.86 V), it still preserves an initial current density of 92%, after 10,000 s of circulation, which is much better than Pt/C (86%). Due to the low cost, high activity and stable ORR property, the prepared non-precious metal electrocatalyst will play an important role in the applications of fuel cells. • Porous carbons prepared by a one-step pyrolysis method using enzymolytic lignin. • Successful doping of iron and nitrogen into the framework of mesoporous carbons. • Superior oxygen reduction activity for Fe–N codoped porous carbon. [ABSTRACT FROM AUTHOR]

The research on low-cost, high-performance non platinum group metal (PGM) oxygen reduction reaction (ORR) catalysts is of great significance for the rapid promotion of fuel cells’ practical applications. In this work, Mnâ€"Nâ€"C catalyst with outstanding activity was prepared through using hydrogel formed by coordination of sodium alginate (SA) and Mn2+ as the precursor. During the preparation process, g-C3N4 was added to improve the surface area enrich the pore structure of catalysts, as well as to function as the nitrogen source. Compare with commercial Pt/C catalyst, the optimum Mnâ€"Nâ€"C catalyst possesses extraordinary ORR activity in alkaline electrolytes, with a half-wave potential (E 1/2) of 0.90 V. In addition, the Mnâ€"Nâ€"C catalyst also displays exceptional stability in alkaline and acidic electrolytes, much superior to Pt/C catalyst. [ABSTRACT FROM AUTHOR]

A high-efficiency carbon-based metal catalyst was prepared using inexpensive raw materials and a simple synthetic method to replace the commercial platinum-based catalyst in oxygen reduction reaction (ORR). In this article, clay was used as the template, and residual organic matter after oil adsorption was used as the carbon source and the nitrogen source, respectively. Through ion adsorption, nitrogen-doped porous carbon catalyst (Fe3C/NC) modified by iron carbide was synthesized by high-temperature pyrolysis and etching of clay mineral template. Fe3C/NC was characterized by Fourier-transform infrared spectroscopy (FT-IR), High-resolution transmission electron microscopy (TEM) and X-ray diffractometer. Further experiment showed that this catalyst had good electrochemical activity for ORR. In this paper, we use the organic matter in the waste clay as the carbon source and nitrogen source and use the characteristics of clay in the waste clay to introduce iron ions into the reaction. After high-temperature calcination, we get Fe3C/NC composite. Fe-N co-doping can expose more graphite defects and more active sites, which can also improve the electrocatalytic performance of ORR. [ABSTRACT FROM AUTHOR]

[Display omitted] Nitrogen- and transition metal-dual doped carbon materials with low cost and high catalytic performances are considered as one of promising alternatives for noble metal catalysts in acceleration of oxygen reduction reaction (ORR). In this work, three-dimensional (3D) self-supporting superstructures of iron carbide (Fe 3 C) nanoclusters entrapped in manganese (Mn)- and nitrogen (N)-dual doped carbon nanosheets covered with double-sided nanoneedles carbon arrays (Fe 3 C/Mn,N-NCAs) are simply synthesized by a coordination pyrolysis method, in which dicyandiamide mainly behaves as nitrogen source and 1-(2-pyridylazo)-2-naphthol (PAN) as carbon source. Integration of the unique 3D self-supporting superstructures and synergistic effects of the multi-compositions, the as-obtained catalyst displays appealing ORR performance such as the much positive onset potential (E onset = 0.98 V vs. RHE) and half-wave potential (E 1/2 = 0.88 V vs. RHE), as well as a just 10 mV negative shift in E 1/2 after 2000 cycles, surpassing commercial Pt/C. This work provides some valuable perspectives for preparation of high-efficiency and low-cost non-noble metal ORR electrocatalysts in energy transformation and storage correlated systems. [ABSTRACT FROM AUTHOR]

While nitrogen (N)-doped carbon can facilitate the four-electron transfer in oxygen reduction reaction (ORR), its effect on the two-electron path is yet to be investigated. To date, the random N-C bond configurations in N-doped carbons make it difficult to identify the active sites for electrochemical reactions. Here, we report a preparation of well-controlled N-C configurations with high centrality as model catalysts for identification of active sites for two-electron transfer ORR. Specifically, the synthesized Pyrrolic-N doped single-wall carbon nanotube and graphene utilizing a microwave-assisted pulse heating method, exhibit excellent activity for two-electron path (H 2 O 2 selectivity of 93.5% and 98.35%). X-ray adsorption near-edge structure spectroscopy measurements indicate that carbon atoms adjacent to Pyrrolic-N are the active sites for two-electron transfer. This work provides a viable way for the fabrication of tailored N configurations in carbon materials and significantly advances our understanding of the N moieties for the electrochemical H 2 O 2 generation. Well-defined graphitic, pyrrolic and pyridinic nitrogen with high centrality doped carbon materials are novelly fabricated by a microwave-assisted pulse heating method under second timescale. The as-obtained high percentage of Pyrr-N doped SWCNT or graphene could exhibit extraordinary performance for electrocatalytic hydrogen peroxide. These ideal model catalysts have scientific significance to identify the active sites of N doped carbon for ORR with two-electron transfer pathway. [Display omitted] [ABSTRACT FROM AUTHOR]