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Optimization of Pt atom utilization efficiency is critical for the development of proton-exchange-membrane fuel cells. Here we aim to develop an efficient oxygen reduction reaction (ORR) catalyst with a low Pt content through the concurrent modification of Pt-Co alloy catalysts and carbon substrate. In the present study, ultrafine Pt-Co alloy nanoparticles are successfully synthesized and stabilized by topological carbon defects via adopting the ammonia thermal treatment. Despite the low Pt loading, the obtained catalyst exhibits an impressive half-wave potential of 0.926 V versus the reversible hydrogen electrode in 0.1 M HClO4 electrolyte. Furthermore, the durability testing using the timed-current method demonstrates a tiny loss of only 3.6% after 12 h. Both experimental results and theoretical calculations demonstrate that topological carbon defects significantly enhance the charge transfer processes at the alloy/carbon interface, contributing to the strong electronic metal-support interactions between the Pt-Co alloy nanoparticles and topological carbon defects. These interactions, along with the alloy effect, play a crucial role in promoting the ORR performance in acidic media. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) represents a cornerstone for many clean energy conversion technologies such as fuel cells and metal‐air batteries. Nevertheless, the commercialization of these technologies is largely impeded by the slow kinetics of ORR, for which active, durable and cost‐effective ORR catalysts are needed. In recent years, zeolitic imidazolate framework (ZIF) derived carbon materials emerge as a new class of non‐precious metal catalysts (NPMCs) toward ORR, largely benefiting from their high surface area, abundant porosity, tunable chemical/electronic structure, and superior ORR activity which is comparable or even surpasses those state‐of‐the‐art Pt‐based ORR catalysts. This review offers a comprehensive overview of the recent advances in ZIF‐derived carbons for ORR. The synthesis strategies and the key factors affecting the ORR performance of ZIF‐derived carbon materials are discussed. Future research directions and perspectives on exploring ZIF derived carbons as efficient ORR catalysts are highlighted, with a focus on the principles of rationally engineering the coordination structures of active sites. [ABSTRACT FROM AUTHOR]

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

Engineering the electronic configuration and intermediates adsorption behaviors of high‐performance non‐noble‐metal‐based catalysts for the sluggish oxygen reduction reaction (ORR) kinetics at the cathode is highly imperative for the development of anion exchange membrane fuel cells (AEMFCs), yet remains an enormous challenge. Herein, a rare‐earth metal oxide engineering tactic through the formation of Fe3O4/La2O3 heterostructures in N,O‐doped carbon nanospheres (Fe3O4/La2O3@N,O‐CNSs) for efficient oxygen reduction electrocatalysis is reported. The theoretical calculations reveal that the interfacial bonds formed by the La─O─Fe heterogeneous interface effectively optimize the electronic structure of the Fe d‐band center relative to the Fermi level, which results in a significant reduction of the reaction barriers of rate‐limiting steps during the ORR. The modulation in intermediates chemisorption enables Fe3O4/La2O3@N,O‐CNSs an outstanding ORR performance and improved stability, with a significantly higher half‐wave potential value (0.88 V). More impressively, this integrated catalyst delivers a remarkable power density of 148.7 mW cm−2 in practical AEMFC operating conditions, along with negligible performance degradation over 100 h using an H2‐air atmosphere, which is higher than commercial Pt/C‐coupled electrodes. The results presented here are believed to provide guidelines for fabricating high‐performance AEMFCs electrocatalysts in terms of heterointerface engineering and strong electronic coupling effect induced by rare‐earth oxides. [ABSTRACT FROM AUTHOR]

An oxygen reduction reaction (ORR) is the key half reaction of proton exchange membrane fuel cells (PEMFCs), and is highly dependent on Pt-based nanocrystals as core electrocatalysts. Despite the exceptional ORR activity from adjusting the electronic structures of surface or near-surface atoms, several serious issues, including the corrosion of carbon supports, the preferential leaching of active metal elements, the instability of surface low-coordinated atoms and the sintering/agglomeration of nanocrystals, still exist, challenging the ORR durability of developed Pt-based ORR catalysts. From the point of view of the catalyst structure design, in this review, we summarized the state-of-the-art structural regulation strategies for improving the ORR durability of Pt-based catalysts. The current limitation of Pt-based binary catalysts for ORR electrocatalysis is firstly discussed, and the detailed strategies are further classified into the optimization of supports, metal-doped alloys, core/shell structures, intermetallics and high-entropy alloys, etc. The structure–performance relationship is detailedly explained, especially emphasizing the elimination of the above restrictions. Finally, the existing challenges and future research direction are further presented, aiming at practicing the PEMFC devices of the ultradurable Pt-based catalysts. [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]

The oxygen reduction and evolution reactions are considered the bottleneck in many electrochemical devices, i. e. fuel cells, water electrolyzers, and metal‐air batteries. The continuous focus has been on inventing and exploring cost‐effective and robust electrocatalysts. Few developed non‐precious metal/metal‐free materials, in fact, outperformed state‐of‐the‐art catalysts during the half‐cell study. However, most of these materials show limited activity during the full cell demonstration, restricting their deployment in commercial energy devices. In this direction, transition metal nitrides (TMNs) have emerged as a potential alternative with peculiar electronic properties and the ease of tuning their intrinsic as well as extrinsic properties. High hardness, refractory nature, d‐band modulation ability and comparatively lower energy for the nitride formation are the other motivations to explore their effectiveness in oxygen electrocatalysis. Considering this, the minireview attempts first to present the properties of catalytic interest, followed by the most viable synthesis approaches in nanoengineering of the TMNs. Next, we provide key trends toward catalytic property modulation for oxygen electrocatalysis, the role of TMNs as potential catalytic support, followed by the effect of TMNs′ in situ autoxidation on the performance. Finally, we state the current limitations of TMNs toward oxygen electrocatalysis, followed by our vision for further advancements. [ABSTRACT FROM AUTHOR]

Abstract Oxygen reduction reaction (ORR) is considered the bottleneck reaction in fuel cells. Its sluggish kinetics requires the use of scarce and expensive platinum group metal (PGM) catalysts. Significant efforts have been invested in trying to find a PGM‐free catalyst to replace Pt for this reaction or reduce its loadings. One interesting family of materials that has shown great promise in doing so is aerogels, which are based on covalent frameworks. The aerogels’ high surface area and porosity enable good mass transport and high catalyst utilization that is expected to lower PGM loadings or replacing them completely. This review summarizes recent research in this field, introducing methods of using aerogels as cathodes for ORR, from carbon to metal aerogels. The catalytic sites vary from nanoparticles to atomically dispersed metal ions embedded in carbon aerogels that form all‐in‐one platform which can serve as both the support and the catalyst.

The harsh working environments of proton exchange membrane fuel cells (PEMFCs) pose huge challenges to the stability of Pt‐based alloy catalysts. The widespread presence of metallic bonds with significantly delocalized electron distribution often lead to component segregation and rapid performance decay. Here we report L10−Pt2CuGa intermetallic nanoparticles with a unique covalent atomic interaction between Pt−Ga as high‐performance PEMFC cathode catalysts. The L10−Pt2CuGa/C catalyst shows superb oxygen reduction reaction (ORR) activity and stability in fuel cell cathode (mass activity=0.57 A mgPt−1 at 0.9 V, peak power density=2.60/1.24 W cm−2 in H2‐O2/air, 28 mV voltage loss at 0.8 A cm−2 after 30 000 cycles). Theoretical calculations reveal the optimized adsorption of oxygen intermediates via the formed biaxial strain on L10−Pt2CuGa surface, and the durability enhancement stems from the stronger Pt−M bonds than those in L11−PtCu resulted from Pt−Ga covalent interactions. [ABSTRACT FROM AUTHOR]

Ternary PtZrNi NRs have excellent electrocatalytic activity in cathode and cathode reactions of fuel cells. [Display omitted] Pt-based alloys with precise structure and composition design have been considered to be effective and robust novel electrocatalysts for fuel cells. Whereas, the sluggish kinetics of oxygen reduction reaction (ORR) and low intrinsic activity of Pt limited their real application on a large scale. Herein, a novel ternary PtZrNi nanorods (PtZrNi NRs) was synthesized via a facile wet-chemical method to achieve high electrocatalytic performance for both ORR and alcohol oxidation reaction owing to the synergism of chosen three elements and prominent one-dimensional morphology. Specifically, the PtZrNi NRs show enhanced mass and specific activities of 0.755 A mg Pt -1 and of 0.97 mA/cm2 at 0.9 V RHE towards ORR in acidic media, which are 4.7 and 4.4 times of those of commercial Pt/C, respectively. Additionally, in alkaline media, the PtZrNi NRs also exhibit superior ORR mass and specific activities of 3.216 A mg Pt -1and 4.13 mA/cm2, enhanced by 34.6 and 31.3 times compared with those of commercial Pt/C, respectively. The PtZrNi NRs retain the nanorod shape well without agglomeration after an accelerated durability test (20000 cycles). This work may offer a new perspective for engineering high-performance Pt-based electrocatalysts for commercial fuel cells. [ABSTRACT FROM AUTHOR]

Platinum group metal‐free catalysts have been considered the most promising alternative for platinum‐based catalysts for the oxygen reduction reaction in fuel cells. Despite the significant advancement made in activity, their viability as fuel cell catalysts is still questionable due to their low durability. So far, deciphering the degradation mechanisms of this class of catalysts has been hampered by their undefined structure. Herein, we used a molecular model catalyst, iron‐phthalocyanine, featuring Fe−N4 active sites with resemblance to those in the more active Fe−N−C catalysts, and studied their degradation mechanisms. Based on X‐ray photoelectron spectroscopy and the electrochemical measurements, three main demetallation processes were identified: at potentials higher than 0.65 V vs. RHE, where the metal center is Fe3+, an electrochemical oxidation of the ligand ring is occurring, between 0.6 and 0.2 V vs. RHE, Fenton reagents are produced and attack the catalyst and support, and at lower voltages, where peroxide is produced by the catalyst and the carbon support. The combination of the different iron oxidation states together with the oxygen species directs to different degradation mechanisms. The decay rates obtained in the stability measurements establish what is mainly causing the loss of activity. Thereby, this model molecule can aid in understanding the degradation mechanisms of other platinum group metal‐free oxygen reduction reaction catalysts. [ABSTRACT FROM AUTHOR]

Low‐cost and high‐efficiency oxygen reduction reaction (ORR) electrocatalysts are the basis for large‐scale applications of electrochemical energy storage and conversion technologies such as fuel cells and metal‐air batteries. Herein, cobalt and oxygen vacancy‐rich cobalt oxide encapsulated in nitrogen‐doped carbon and carbon nanotubes (Co/CoO@NC‐CNTs) have been prepared by direct solid‐state pyrolysis of Co‐MOF. The carbon morphology, oxygen vacancy content and type of nitrogen can be finely tuned by mixing Co‐MOF with proper amounts of melamine. The optimized material has an interwoven CNT structure with abundant micro‐ and mesopores, suitable nitrogen type and certain number of oxygen vacancies and exhibiting outstanding ORR electrocatalytic performance in alkaline media with an onset potential of 0.96 V and a half‐wave potential of 0.88 V vs RHE, which is higher than 20 wt% Pt/C, as well as being highly stable and well resistant to methanol. [ABSTRACT FROM AUTHOR]

Developing cost-effective and high-efficiency oxygen reduction reaction (ORR) catalysts is imperative for promoting the substantial progress of fuel cells and metal-air batteries. The coordination and geometric engineering of single-atom catalysts (SACs) occurred the promising approach to overcome the thermodynamics and kinetics problems in high-efficiency electrocatalysis. Herein, we rationally constructed atomically dispersed Co atoms on porous N-enriched graphene material C2N (CoSA-C2N) for efficient oxygen reduction reaction (ORR). Systematic characterizations demonstrated the active sites for CoSA-C2N is as identified as coordinatively unsaturated Co-N2 moiety, which exhibits ORR intrinsic activity. Structurally, the porous N-enriched graphene framework in C2N could effectively increase the accessibility to the active sites and promote mass transfer rate, contributing to improved ORR kinetics. Consequently, CoSA-C2N exhibited superior ORR performance in both acidic and alkaline conditions as well as impressive long-term durability. The coordination and geometric engineering of SACs will provide a novel approach to advanced catalysts for energy related applications. [ABSTRACT FROM AUTHOR]

Fe−N−C represents the most promising non‐precious metal catalysts (NPMCs) for the oxygen reduction reaction (ORR) in fuel cells, but often suffers from poor stability in acid due to the dissolution of metal sites and the poor oxidation resistance of carbon substrates. In this work, silicon‐doped iron‐nitrogen‐carbon (Si/Fe−N−C) catalysts were developed by in situ silicon doping and metal–polymer coordination. It was found that Si doping could not only promote the density of Fe−Nx/C active sites but also elevated the content of graphitic carbon through catalytic graphitization. The best‐performing Si/Fe−N−C exhibited a half‐wave potential of 0.817 V vs. reversible hydrogen electrode in 0.5 m H2SO4, outperforming that of undoped Fe−N−C and most of the reported Fe−N−C catalysts. It also exhibited significantly enhanced stability at elevated temperature (≥60 °C). This work provides a new way to develop non‐precious metal ORR catalysts with improved activity and stability in acidic media. [ABSTRACT FROM AUTHOR]

Finding high‐performance, low‐cost, efficient catalysts for oxygen reduction reactions (ORR) is essential for sustainable energy conversion systems. Herein, highly efficient and durable iron (Fe) and cobalt (Co)‐supported nitrogen (N) and sulfur (S) co‐doped three‐dimensional carbon nanofibers (FeCo−N, S@CNFs) were synthesized via electrospinning followed by carbonization. The as‐prepared FeCo−N,S@CNFs served as efficient ORR catalysts in alkaline 0.1 m KOH solutions that were N2 and O2‐saturated. The experimental results revealed that FeCo−N,S@CNFs were highly active ORR catalysts with defect‐rich active pyridinic N and pyrrolic N and metal bonds to N and S atom sites, which enhanced the ORR activity. FeCo−N,S@CNFs exhibited a high onset potential (Eonset=0.89 V) and half‐wave potential (E1/2=0.85 V), similar to the electrocatalytic activity of commercial Pt/C. Additionally, the durability of the as‐prepared FeCo−N,S@CNFs catalysts was maintained for 14 h with long‐term stability and high tolerance to methanol stability, accounting for their excellent catalytic ability. Furthermore, Co−N@CNFs, Fe−N@CNFs, and varying Fe and Co ratios were compared with those of FeCo−N,S@CNFs. Synergistic interactions between metals and heteroatoms were believed to play a significant role in enhancing the ORR activity. Owing to their excellent catalytic reduction ability, the as‐prepared FeCo−N,S@CNFs can be widely used in battery‐based systems and replace commercial Pt/C in fuel cell applications. [ABSTRACT FROM AUTHOR]

Abstract Platinum group metal‐free catalysts have been considered the most promising alternative for platinum‐based catalysts for the oxygen reduction reaction in fuel cells. Despite the significant advancement made in activity, their viability as fuel cell catalysts is still questionable due to their low durability. So far, deciphering the degradation mechanisms of this class of catalysts has been hampered by their undefined structure. Herein, we used a molecular model catalyst, iron‐phthalocyanine, featuring Fe−N4 active sites with resemblance to those in the more active Fe−N−C catalysts, and studied their degradation mechanisms. Based on X‐ray photoelectron spectroscopy and the electrochemical measurements, three main demetallation processes were identified: at potentials higher than 0.65 V vs. RHE, where the metal center is Fe3+, an electrochemical oxidation of the ligand ring is occurring, between 0.6 and 0.2 V vs. RHE, Fenton reagents are produced and attack the catalyst and support, and at lower voltages, where peroxide is produced by the catalyst and the carbon support. The combination of the different iron oxidation states together with the oxygen species directs to different degradation mechanisms. The decay rates obtained in the stability measurements establish what is mainly causing the loss of activity. Thereby, this model molecule can aid in understanding the degradation mechanisms of other platinum group metal‐free oxygen reduction reaction catalysts.

Exploring low‐cost and high‐efficient electrocatalyst is an exigent task in developing novel sustainable energy conversion systems, such as fuel cells and electrocatalytic fuel generations. 2D materials, specifically 2D superlattice materials focused here, featured highly accessible active areas, high density of active sites, and high compatibility with property‐complementary materials to form heterostructures with desired synergetic effects, have demonstrated to be promising electrocatalysts for boosting the performance of sustainable energy conversion and storage devices. Nevertheless, the reaction kinetics, and in particular, the functional mechanisms of the 2D superlattice‐based catalysts yet remain ambiguous. In this review, based on the recent progress of 2D superlattice materials in electrocatalysis applications, the rational design and fabrication of 2D superlattices are first summarized and the application of 2D superlattices in electrocatalysis is then specifically discussed. Finally, perspectives on the current challenges and the strategies for the future design of 2D superlattice materials are outlined. This review attempts to establish an intrinsic correlation between the 2D superlattice heterostructures and the catalytic properties, so as to provide some insights into developing high‐performance electrocatalysts for next‐generation sustainable energy conversion and storage. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) are polyatomic ions with closed three-dimensional frameworks. Their unique structure contains a large number of redox active sites, making them promising electrocatalysts for electrochemical energy conversion and storage applications. Thus, this paper presents an overview of the use of POMs as electrocatalysts for electrochemical energy conversion and storage devices, such as batteries, supercapacitors, fuel cells, or water electrolyzers. A discussion of the viability of these materials as alternatives to noble metal-based electrocatalysts is made. The current status of these materials to respond to the challenges of converting modern energy systems into more sustainable ones is also envisaged. [ABSTRACT FROM AUTHOR]

The development of highly active and long‐term stable electrocatalysts for the cathode of proton‐exchange membrane fuel cells (PEMFC) is a paramount requirement for high performance and durable PEMFC stacks. In this regard, alloying Pt with rare earth metals (REM) has emerged as a promising approach. This short review summarizes and discusses the most relevant advances on Pt‐REM alloy electrocatalysts, from bulk polycrystalline surfaces to carbon supported nanostructures, for the oxygen reduction reaction (ORR), and their implementation in PEMFCs, and is a starting point to establish the challenges in synthesis and design and properties goals for novel Pt‐REM alloys. [ABSTRACT FROM AUTHOR]

Graphene supported FeN5 active sites, exhibiting high activity and stability of oxygen reduction reaction, enable a H2-air fuel cell to decay little during the latter 20–100 h operation. [Display omitted] • Electrochemically-exfoliated graphene improves forming FeN 5 with NH 3. • Graphene benefits catalytic stability of oxygen reduction reaction. • Fuel cell keep stable with little decay in latter 80 h operation. • High half-wave potentials in alkaline medium (0.940 V). Metal-nitrogen-carbon catalytic material, generally thought as a promising low-cost electrocatalyst of oxygen reduction reaction (ORR), surfers from long-term catalytic durability for fuel cell and metal-air battery. Here, we describe an approach of synthesizing electrochemically exfoliated graphene supported penta-nitrogen coordinated iron exhibiting encouraging ORR catalytic activity and durability. The synthesized catalyst exhibits high half-wave potentials in alkaline medium (E 1/2 0.940 V) enabling high-performance zinc-air battery and in acidic condition for durable fuel cell with a high peak power density (630 mW cm−2). The current density of a proton exchange membrane fuel cell loading the catalyst as cathode tends to decay little after initial hours under H 2 -air measurement, remarkably inhibiting commonly decline tendency of iron–nitrogen-carbon catalysts. DFT calculation combined with extensive experimental investigations demonstrate that penta-nitrogen coordinated iron supported by graphene is thermodynamically stable, and thus benefits the catalytic stability of ORR. [ABSTRACT FROM AUTHOR]

The exploration of non-Pt catalysts with high electrocatalytic activity and durability is especially important for cathodic oxygen reduction reaction (ORR) in fuel cell. Here, cobalt and nitrogen doped hollow carbon sphere-bamboo like carbon nanotube (Co/NHCS-BCNT) is prepared by using SiO 2 sphere as sacrificial template. Co nanoparticles are confined in the cavity and top end of the in-situ formed BCNT, which can not only avoid the agglomeration of Co nanoparticles but also inhibit corrosion in caustic electrolyte. The synergistic effect between NHCS and well-dispersed Co particles makes Co/NHCS-BCNT have superior catalytic activity toward ORR. The electrochemical surface area (ECSA) of Co/NHCS-BCNT is 222 cm2, which is higher than those of NHCS (164 cm2) and HCS (135 cm2). The onset potential and half-wave potential of Co/NHCS-BCNT are 0.941 V and 0.814 V, respectively, which are close to commercial Pt/C (0.949 V, 0.807 V). The Tafel slope of Co/NHCS-BCNT (63.8 mV dec-1) is lower than that of Pt/C (71.7 mV dec-1). In addition, Co/NHCS-BCNT shows excellent durability and fuel selectivity. [Display omitted] [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) as the crucial reaction in fuel cells (FCs), requires high-performance electrocatalysts to achieve satisfied kinetics. Commercial electrocatalysts are generally based on Pt, but the high cost hinders the large-scale application of FCs. Many efforts have been made on non-noble metal electrocatalysts (NNMEs) as potential alternatives to Pt. Among them, transition metallomacrocycles (TMs) based electrocatalysts (TMEs) are one kind of the most efficient NNMEs. In this review, the catalytic characteristics of these TMEs based on two representatives: FeN 4 - and CoN 4 -centered TMs are summarized for ORR. The variation of ORR performances is reviewed based on the strategies to modify the active sites, conductivity, and morphology, including adjusting molecular structures, altering carbon supports and employing metal–organic-frameworks (MOFs) as precursors. Moreover, the prospects and challenges of such electrocatalysts and the corresponding solutions are also discussed in details. From this review, we will understand more clearly about the structure–activity relationship of TMEs based on FeN 4 - and CoN 4 -centered TMs in ORR, which will pave the way for the rational design of more TMEs based on MN 4 -centered TMs in the future. [ABSTRACT FROM AUTHOR]

• Resonance structure as substrate molecules are introduced to form highly ordered PtCo alloys. • Synthesis of PtM (Co, Fe, Ni) ordered alloys use the same low temperature heat treatment conditions. • The ordered PtCo shows efficient electrocatalytic performance. Platinum-based ordered alloys have excellent catalytic performance for the cathodic oxygen reduction reaction (ORR) in fuel cells. However, these alloys exhibit a lower degree of ordering and larger crystal grains after heat treatment. Herein, a series of cyanamide group molecules (cyanamide, dicyandiamide, melamine) was employed as substrates to modify Pt-based alloys by promoting the binding between metal ions, leading to the preparation of ∼ 4 nm PtM (M = Co, Fe, Ni) ordered alloys after heat treatment. Among them, the PtCo ordered alloy prepared using hydrolyzed cyanamide with a unique resonance structure exhibits a high degree of order (93.1 %), and its mass activity of 0.915 A mg Pt -1 at 0.9 V is superior to that of Pt/C. The theoretically calculated adsorption energies of these alloys demonstrate that the resonance structure of the cyanamide substrate is beneficial for alloy formation, thereby facilitating ordered alloy synthesis. [ABSTRACT FROM AUTHOR]

This study presents the preparation of tridoped Fe, N, S carbon-based catalysts using ZIF-8 as the main carbon source and iron(II)acetate, 1,10-phenanthroline, ammonia gas and thiourea as precursors for Fe, N and S elements. Thiourea was mixed via planetary ball-milling with a Fe–N–C catalyst prepared by inert gas pyrolysis, and different pyrolysis conditions were applied thereafter. The main goal of the work is to synthesise active non-precious metal electrocatalysts for oxygen reduction reaction (ORR). High electrocatalytic ORR activity in alkaline media was observed for the two materials obtained after thiourea addition and subsequent pyrolysis. Physico-chemical characterisation revealed successful S- and N-doping for all three catalysts with enhanced porosity for the two materials that were subjected to additional pyrolysis after the thiourea addition. The sulphur doping was highest for the FeNSC3 material that was subjected to a second pyrolysis in N 2 and a third pyrolysis in NH 3 , compared to the FeNSC2 material that was subjected to a single pyrolysis in NH 3 flow after thiourea addition. The ORR activity of FeNSC2 with half-wave potential of 0.88 V was slightly higher than that of FeNSC3, and the former was selected for evaluation as a cathode catalyst in an anion-exchange membrane fuel cell. [Display omitted] [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]

A new isolation protocol was recently reported for highly purified metallic Fullertubes D5h‐C90, D3d‐C96, and D5d‐C100, which exhibit unique electronic features. Here, we report the oxygen reduction electrocatalytic behavior of C60, C70 (spheroidal fullerenes), and C90, C96, and C100 (tubular fullerenes) using a combination of experimental and theoretical approaches. C96 (a metal‐free catalyst) displayed remarkable oxygen reduction reaction (ORR) activity, with an onset potential of 0.85 V and a halfway potential of 0.75 V, which are close to the state‐of‐the‐art Pt/C benchmark catalyst values. We achieved an excellent power density of 0.75 W cm−2 using C96 as a modified cathode in a proton‐exchange membrane fuel cell, comparable to other recently reported efficient metal‐free catalysts. Combined band structure (experimentally calculated) and free‐energy (DFT) investigations show that both favorable energy‐level alignment active catalytic sites on the carbon cage are responsible for the superior activity of C96. [ABSTRACT FROM AUTHOR]

Proton exchange membrane (PEM) fuel cells using Pt-based materials as electrocatalysts have achieved a decent performance, represented by the launched Toyota Mirai vehicle. The ideal PEM fuel cells consume stored pure hydrogen and air. However, SO2, as a primary air contaminant, may be fed along with air at the cathode, leading to Pt site deactivation. Therefore, it is important to improve the SO2 tolerance of catalysts for the stability of the oxygen reduction reaction (ORR). In this work, we develop the Pt/C-TiO2 catalyst against SO2 poisoning during ORR. Impressively, the hybrid Pt/C-TiO2 catalyst with 20 mass % TiO2 shows the best ORR and anti-toxic performance: the kinetic current density of ORR is 20.5% higher and the degradation rate after poisoning is 50% lower than Pt/C. The interaction between Pt and TiO2 as well as the abundant hydroxyl groups on the surface of TiO2 are both revealed to account for the accelerated removal of poisonous SO2 on Pt surfaces. [ABSTRACT FROM AUTHOR]

The development of new synthetic methods for methanol-tolerant catalysts with improved performance is of fundamental importance for the commercialization of fuel cells. Herein, we reported a facile displacement reaction-assisted synthesis of graphene-supported sub-nanometer Pt/Bi catalysts (Pt/Bi/rGO). Bismuth (0) nanoparticles produced by NH3BH3 reduction can be further dissolved into the ethylene glycol, implying Bi(0) has a strong interaction with the hydroxyl group. That is the key interaction between Bi(0) and the functional group on the rGO to form the ultra-small Bi/rGO catalyst. Furthermore, Pt clusters are obtained by the displacement between Bi(0) and HPtCl4 and are directly anchored to the rGO surface. The as-synthesized Pt/Bi/rGO catalyst exhibits high oxygen reduction mass activity and high tolerance to methanol poisoning. In the presence of 0.5 mol/L CH3OH, the initial potential and activity of ORR were almost unchanged, which demonstrated great potential in the application of direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

Opening up electrocatalysts for oxygen reduction reaction (ORR) is essential for practical application in fuel cells and metal-air batteries; however, how to make the catalysts with both good performance and low cost is difficult. Recently, research on the ORR of molybdenum disulfide-based catalysts in alkaline electrolytes has been on the rise. However, the development of MoS2 catalyst for acidic ORR is still in its infancy. Herein, without using reductant and morphology control reagent, we firstly obtained flowerball-like MoS2/Vulcan XC-72R (VC) nanocomposites via hydrothermal method. The designed composite exhibits a nearly 4e− ORR process with 0.78 and 0.92 V onset potentials in 0.1 M KOH and HClO4, respectively. Furthermore, the flowerball-like composite shows utmost electrochemical stability judging by 87 and 80% current retention for about 5.5 h either in alkaline or acid media, long term durability for continuous 10,000 cycles, and stronger resistance to methanol than the commercial Pt/C catalyst. The abundant Mo edges as catalytic active centers of flowerball-like structure, high electron conductivity, and enhanced mass transport in either alkaline or acidic electrolyte are favorable for catalytic performance. The prepared catalyst provides great potential for the substitution of noble metal based catalysts in fuel cells and metal-air batteries. [ABSTRACT FROM AUTHOR]

Developing efficient and stable Pt‐based oxygen reduction reaction (ORR) catalysts is a way to promote the large‐scale application of fuel cells. Pt‐based alloy nanowires are promising ORR catalysts, but their application is hampered by activity loss caused by structural destruction during long‐term cycling. Herein, the preparation of ordered PtFeIr intermetallic nanowire catalysts with an average diameter of 2.6 nm and face‐centered tetragonal structure (fct‐PtFeIr/C) is reported. A silica‐protected strategy prevents the deformation of PtFeIr nanowires during the phase transition at high temperature. The as‐prepared fct‐PtFeIr/C exhibited superior mass activity for ORR (2.03 A mgPt−1) than disordered PtFeIr nanowires with face‐centered cubic structure (1.11 A mgPt−1) and commercial Pt/C (0.21 A mgPt−1). Importantly, the structure and electrochemical performance of fct‐PtFeIr/C were maintained after stability tests, showing the advantages of the ordered structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen reduction reaction (ORR) has been extensively used in fuel cells and rechargeable metal-air batteries. • This review details the latest developments in ORR electrocatalyst development. • These electrocatalysts specifically include platinum group metals (PGM), transition metals and carbon-based catalysts. • The preparation and ORR performance of various electrocatalysts are discussed in detail. • Speculation and discussion on the development prospects and challenges of ORR electrocatalysts. Oxygen reduction reaction (ORR) has gradually been in the limelight in recent years because of its great application potential for fuel cells and rechargeable metal-air batteries. Therefore, significant issues are increasingly focused on developing effective and economical ORR electrocatalysts. This review begins with the reaction mechanisms and theoretical calculations of ORR in acidic and alkaline media. The latest reports and challenges in ORR electrocatalysis are traced. Most importantly, the latest advances in the development of ORR electrocatalysts are presented in detail, including platinum group metal (PGM), transition metal, and carbon-based electrocatalysts with various nanostructures. Furthermore, the development prospects and challenges of ORR electrocatalysts are speculated and discussed. These insights would help to formulate the design guidelines for highly-active ORR electrocatalysts and affect future research to obtain new knowledge for ORR mechanisms. [ABSTRACT FROM AUTHOR]

The replacement of Pt/C catalysts with iron−nitrogen−carbon (Fe−N−C) nanomaterials in the oxygen reduction reaction (ORR) is appealing for the large‐scale application of fuel cells. Herein, an extended Stöber method was used to in situ synthesize Fe−N co‐doped porous carbon spheres (Fe−N−Cs) with large surface areas and impressive ORR performance. Fe−N−Cs were synthesized using 3‐aminophenol as N precursor, ferrocenealdehyde (Fc−CHO) as Fe source and crosslinker, and Pluronic F127 as soft template. Among all prepared catalysts, Fe−N−Cs‐1.0 exhibits much enhanced ORR activities. The initial potential and half‐wave potential are 0.992 V, 0.873 V (vs. RHE) and 0.981 V, 0.871 V in alkaline and acidic media, respectively, which are higher than that of commercial Pt/C catalyst (0.986 V, 0.868 V and 0.979 V, 0.843 V). Meanwhile, the methanol tolerance and durability of Fe−N−Cs‐1.0 were far better than Pt/C. This work manifests the Fe−N−Cs electrocatalysts are expected to replace the commercial Pt/C catalyst in the area of ORR. [ABSTRACT FROM AUTHOR]

In this work copper oxide nanoparticles (CuONPs) are prepared from precursor CuSO4.5H2O using plant leaves extract (PEE) of Eranthemum pulchellum(E. pulchellum).The synthesized CuONPs are characterized by ultraviolet visible (UV‐vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD) and transmission electron microscopy (TEM). CuONPs are distorted spherical in shape, with the sizes ranging from 5 to 17 nm. PEE and CuONPs are coated on glassy carbon (GC) electrode and abbreviated as GC/PEE and GC/CuONPs, respectively. The modified electrodes GC/PEE and GC/CuONPs are characterized with cyclic voltammetry (CV) techniques. The modified electrode GC/CuONPs exhibits good electrocatalytic activity for oxygen reduction reaction (ORR). GC/CuONPs also shows excellent operational stability up to 1000 CV cycles. [ABSTRACT FROM AUTHOR]

The highly efficient energy conversion of the polymer‐electrolyte‐membrane fuel cell (PEMFC) is extremely limited by the sluggish oxygen reduction reaction (ORR) kinetics and poor electrochemical stability of catalysts. Hitherto, to replace costly Pt‐based catalysts, non‐noble‐metal ORR catalysts are developed, among which transition metal–heteroatoms–carbon (TM–H–C) materials present great potential for industrial applications due to their outstanding catalytic activity and low expense. However, their poor stability during testing in a two‐electrode system and their high complexity have become a big barrier for commercial applications. Thus, herein, to simplify the research, the typical Fe–N–C material with the relatively simple constitution and structure, is selected as a model catalyst for TM–H–C to explore and improve the stability of such a kind of catalysts. Then, different types of active sites (centers) and coordination in Fe–N–C are systematically summarized and discussed, and the possible attenuation mechanism and strategies are analyzed. Finally, some challenges faced by such catalysts and their prospects are proposed to shed some light on the future development trend of TM–H–C materials for advanced ORR catalysis. [ABSTRACT FROM AUTHOR]

Abstract The highly efficient energy conversion of the polymer‐electrolyte‐membrane fuel cell (PEMFC) is extremely limited by the sluggish oxygen reduction reaction (ORR) kinetics and poor electrochemical stability of catalysts. Hitherto, to replace costly Pt‐based catalysts, non‐noble‐metal ORR catalysts are developed, among which transition metal–heteroatoms–carbon (TM–H–C) materials present great potential for industrial applications due to their outstanding catalytic activity and low expense. However, their poor stability during testing in a two‐electrode system and their high complexity have become a big barrier for commercial applications. Thus, herein, to simplify the research, the typical Fe–N–C material with the relatively simple constitution and structure, is selected as a model catalyst for TM–H–C to explore and improve the stability of such a kind of catalysts. Then, different types of active sites (centers) and coordination in Fe–N–C are systematically summarized and discussed, and the possible attenuation mechanism and strategies are analyzed. Finally, some challenges faced by such catalysts and their prospects are proposed to shed some light on the future development trend of TM–H–C materials for advanced ORR catalysis.

The development of active and stable platinum (Pt)‐based oxygen reduction reaction (ORR) electrocatalysts with good resistance to poisoning is a prerequisite for widespread practical application of fuel cells. An effective strategy for enhancing the electrocatalytic performance is to tune or control the physicochemical state of the Pt surface. Herein, we show a general surface‐engineering approach to prepare a range of nanostructured Pt alloys by coating with alloy PtBi shells. FePt@PtBi core–shell nanoparticles showed the best ORR performance with a mass activity of 0.96 A mgPt−1 and a specific activity of 2.06 mA cm−2, respectively 7 times and 11 times those of the corresponding values for benchmark Pt/C. Moreover, FePt@PtBi shows much better tolerance to methanol and carbon monoxide than conventional Pt‐based electrocatalysts. The observed comprehensive enhancement in ORR performance of FePt@PtBi can be attributed to the increased compressive strain of the Pt surface due to in‐plane shearing resulting from the presence of the large Bi atoms in the surface‐structured PtBi overlayers, as well as charge displacement via Pt‐Bi bonding which mitigates crossover issues. [ABSTRACT FROM AUTHOR]

Efficient electrocatalysis of the oxygen reduction (ORR) and evolution (OER) reactions is essential in numerous renewable energy conversion systems, such as fuel cells, metal‐air batteries, and water electrolyzers. Design and optimization of electrocatalytic materials for such systems primarily rely on understanding the nature of active centers on the catalyst surface. This review focuses on several important aspects of the experimental identification of active sites on various model bifunctional ORR/OER electrocatalytic surfaces. Applications of the state‐of‐the‐art experimental techniques are analyzed. In addition, approaches to investigate and understand the influence of some supporting electrolyte components on the ORR and OER activities are discussed. [ABSTRACT FROM AUTHOR]

The poor kinetics of oxygen reduction reaction (ORR) invites a quest for the development of low-cost and efficient non-Pt electrocatalysts for fuel cells. Herein, a nanocomposite (g-[Co 2 N 8 ]) was synthesized by coordination assembly of CoN 4 macrocyclic moieties on graphene surface. The CoN 4 macrocyclic complex was characterized by UV–Vis, FT-IR, Mass, 1H NMR and 13C NMR spectral studies, whereas UV–Vis, FT-IR, and Mass spectral, Raman, XRD and TEM studies were utilized to characterize the nanocomposite g-[Co 2 N 8 ]. The results suggested that [CoN 4 ] units are present in self-assembled [Co 2 N 8 ] species. Further, the nanocomposite g-[Co 2 N 8 ] was examined for ORR activity by employing cyclic and linear sweep voltammetry and found that the formal potential (E 1/2) of g-[Co 2 N 8 ] (+0.90 V) was more positive than 20% Pt/C (+0.86 V), indicating a remarkable ORR performance of g-[Co 2 N 8 ] in comparison to 20% Pt/C, followed by 4e-mechanism. Moreover, the nanocomposite (g-[Co 2 N 8 ]) displayed better ORR activity in comparison to [CoN 4 ] complex which can be attributed to the synergistic incorporation of endo and exo N 4 –Co2+ moieties in the [Co 2 N 8 ] species. In addition, g-[Co 2 N 8 ] electrocatalyst exhibited a comparable stability to 20% Pt/C catalyst after 5000 cycles. This work will help to design multi-metallic coordination polymers with similar or different metal ions in N 4 -arrangement for various energy related electrocatalysis. [Display omitted] • CoN 4 -complex was synthesized and characterized. • Self-assembly of CoN 4 -complex was carried out using coordination strategy. • Self-assembled molecular catalyst immobilized on graphene synthesized and fully characterized. • Self-assembled molecular catalyst immobilized on graphene exhibited excellent ORR activity. [ABSTRACT FROM AUTHOR]

Ultrathin nanosheet catalysts deliver great potential in catalyzing the oxygen reduction reaction (ORR), but encounter the ceiling of the surface atomic utilizations, thus presenting a challenge associated with further boosting catalytic activity. Herein, a kind of PdPtCu ultrathin nanorings with increased numbers of electrocatalytically active sites is reported, with the purpose of breaking the activity ceiling of conventional catalysts. The as‐made PdPtCu nanorings possess abundant high‐index facets at the edge of both the exterior and interior surfaces. An ultrahigh electrochemical active surface area of 92.2 m2 g–1PGM is achieved on this novel catalyst, much higher than that of the commercial Pt/C catalyst. The optimized Pd39Pt33Cu28/C shows a great enhanced ORR activity with a specific activity of 2.39 mA cm–2 and a mass activity of 1.97 A mg–1PGM at 0.9 V (versus RHE), as well as superior durability within 30 000 cycles. Density function theory calculations reveal that the high‐index facets and alloying Cu atoms can optimize the oxygen adsorption energy, explaining the enhanced ORR activity. Overcoming a key technical barrier in sub‐nanometer electrocatalysts, this work successfully introduces the hollow structures into the ultrathin nanosheets, heralding the exciting prospects of high‐performance ORR catalysts in fuel cells. [ABSTRACT FROM AUTHOR]

Ligand and strain effects can tune the adsorption energy of key reaction intermediates on a catalyst surface to speed up rate‐limiting steps of the reaction. As novel fields like high‐entropy alloys emerge, understanding these effects on the atomic structure level is paramount: What atoms near the binding site determine the reactivity of the alloy surface? By statistical analysis of 2000 density functional theory calculations and subsequent host/guest calculations, it is shown that three atomic positions in the third layer of an fcc(111) metallic structure fourth‐nearest to the adsorption site display significantly increased influence on reactivity over any second or third nearest atomic positions. Subsequently observed in multiple facets and host metals, the effect cannot be explained simply through the d‐band model or a valence configuration model but rather by favorable directions of interaction determined by lattice geometry and the valence difference between host and guest elements. These results advance the general understanding of how the electronic interaction of different elements affect adsorbate–surface interactions and will contribute to design principles for rational catalyst discovery of better, more stable and energy efficient catalysts to be employed in energy conversion, fuel cell technologies, and industrial processes. [ABSTRACT FROM AUTHOR]

Summary: Improving the stability and efficiency of non‐noble metal based ORR (oxygen reduction reaction) electrocatalyst is crucial for the commercialization of fuel cell technology. Here, we report the synthesis of cobalt‐polyoxometalate nanocomposite with carbon (CoP@C) by greener strategy, which shows an interesting enhancement in the kinetics of oxygen electroreduction process. The CoP@C nanocomposite exhibited improved catalytic activity toward ORR with Eonset 1.00 V vs RHE and current density of 4.2 mA/cm2 at 1600 rpm in alkaline condition. Further, CoP@C electrocatalyst showed a single step ~4 electron transfer pathway, high tolerance to methanol, and exhibited superior stability compared with 20 wt% Pt/C. Thus, CoP@C could be a cheaper and potential candidate for ORR electrocatalysis in fuel cells. The superiority of the catalyst in terms of activity and durability arises due to the uniform distribution of cobalt‐polyoxometalate nanoclusters on carbon surface and the synergetic effect of POM, cobalt, and carbon. [ABSTRACT FROM AUTHOR]

Designing efficient and stable single-atom catalysts (SACs) for the oxygen reduction reaction (ORR) is essential to promote fuel cell commercialization. In this study, the Bayesian Regularization Neural Network (BRNN) has been used to determine the carbothermal shock (CTS) conditions for preparing high-loading Pt-Fe/C SACs. The BRNN model effectively identified a low reaction temperature of 283 °C for achieving high-loading (15 wt %) Pt-Fe/C SACs. Based on this model, we successfully synthesized Pt-Fe/C SACs with a metal mass content of 11.31 wt % using the CTS method. These ultrahigh content metal Pt-Fe/C SACs consisted of dispersed single atoms and foam-like atomic constructions, namely Pt-Fe/C atom foam catalysts (AFCs), rendered them promising candidates for electrocatalysis applications. The Pt-Fe/C AFCs exhibited good catalytic activity and durability toward ORR in alkaline conditions. The Pt-Fe/C AFCs were employed in a direct borohydride fuel cell (DBFC) as cathode catalyst, which resulted in a maximum power density of 214 mW cm−2 at 60 °C and demonstrated stable discharge for 40 h at room temperature. The electrocatalytic performance of the Pt-Fe/C AFCs surpassed that of low-loading Pt-Fe/C SACs and commercial Pt/C catalysts. The rapid ramp-up rate and the rapid cooling rate of the CTS process enabled the incorporation of high-loading Pt and Fe metal atoms into the graphitized carbon layer, resulting in an increased number of active sites of the Pt-Fe/C AFCs. This work provides an effective strategy for manufacturing efficient and stable SACs for practical applications in fuel cells. [Display omitted] • The Bayesian Regularization Neural Network is used to determine the CTS conditions. • Pt-Fe/C AFCs with metal content of 11.31 wt % is successfully synthesize by the CTS method. • The Pt-Fe/C AFCs exhibit good catalytic activity and durability towards ORR. • The DBFC using Pt-Fe/C AFCs cathode achieves a maximum power density of 214 mW cm−2. [ABSTRACT FROM AUTHOR]

Developing highly stable and efficient catalysts toward the oxygen reduction reaction is important for the long‐term operation in proton exchange membrane fuel cells. Reported herein is a facile synthesis of two‐dimensional coplanar Pt‐carbon nanomeshes (NMs) that are composed of highly distorted Pt networks (neck width of 2.05±0.72 nm) and carbon. X‐ray absorption fine structure spectroscopy demonstrated the metallic state of Pt in the coplanar Pt/C NMs. Fuel cell tests verified the excellent activity of the coplanar Pt/C NM catalyst with the peak power density of 1.21 W cm−2 and current density of 0.360 A cm−2 at 0.80 V in the H2/O2 cell. Moreover, the coplanar Pt/C NM electrocatalysts showed superior stability against aggregation, with NM structures preserved intact for a long‐term operation of over 30 000 cycles for electrode measurement, and the working voltage loss was negligible after 120 h in the H2/O2 single cell operation. Density‐functional theory analysis indicates the increased vacancy formation energy of Pt atoms for coplanar Pt/C NMs, restraining the tendency of Pt dissolution and aggregation. [ABSTRACT FROM AUTHOR]

A development of electrocatalyst for oxygen reduction reaction (ORR) is one of the crucial reactions for low temperature fuel cell applications. The state-of-the-art catalyst (platinum based) have various limitations such as low abundance, extortionate price and sensitive towards impurities. Therefore, design of high performance non-platinum electrocatalyst is the most challenging issue for low temperature fuel cell. In this work, we discuss the nitrogen doping at defect sites of multiwalled carbon nanotubes (MWCNTs) using melamine foam as a template for efficient CNT assembly with subsequent role of different nitrogen containing agents such as melamine and hexamine. Templated assembly of functionalized CNT through melamine foam provides easy approach towards nitrogen doping that followed effective exposure of active sites (like pyridinic-N and oxidic-N) for electroreduction of oxygen. As-prepared N-CNT catalysts (prepared using both the precursors) show better ORR activity than Pt/C in alkaline medium. A sharp reduction peak in their cyclic voltammogram under O 2 -saturated 0.1 M KOH solution proves their activity towards ORR electrocatalysis. More interestingly, the onset potentials of ~0.92 V and ~1.1 V versus RHE for N-CNT obtained by hexamine and melamine respectively indicate superior onsets than that of Pt/C (~1.04 V vs RHE). Furthermore, the best N-CNT catalyst (obtained by melamine) reveals better stability up to 15,000 cycles than Pt/C with zero response towards methanol, exhibiting an excellent methanol tolerance. A controlled N-doping using melamine foam as a template could furnish remarkable efficiency of oxygen electroreduction. Image 1 • An approach, providing an interesting comparison of N-doping in CNT using different precursors. • Mel-NCNT exhibits superior E onset of 1.1 V and J L 5.7 mA/cm2 at 1600 rpm. • Mel-CNT shows stability up to 15,000 potential cycles. • ORR activity of N-doped CNT depends on the physical properties of precursors. [ABSTRACT FROM AUTHOR]