Significant progress has been made in the development of non-precious metal electrocatalysts (NPMEs) during the past decade. Correspondingly, there is an urgent demand for an appropriate measurement method to be est...Significant progress has been made in the development of non-precious metal electrocatalysts (NPMEs) during the past decade. Correspondingly, there is an urgent demand for an appropriate measurement method to be established for the reliable evaluation of NPMEs. In this study, platinum and graphite counter electrodes were used to investigate the impact of counter electrode material on the accelerated durability testing (ADT) of NPMEs in acidic medium. Platinum used as the coun- ter electrode in a traditional three-electrode electrochemical cell was found to dissolve in acidic medium and re-deposit on NPME coated on the working electrode during ADT. Such re-deposition causes the oxygen reduction reaction (ORR) performance of NPMEs to remarkably improve, and thus will seriously mislead our judgment of NPMEs if we are unaware of it. The phenomenon can be avoided using a graphite counter electrode.展开更多
The oxygen reduction/evolution reactions(ORR/OER) are a key electrode process in the development of electrochemical energy conversion and storage devices,such as metal-air batteries and reversible fuel cells.The searc...The oxygen reduction/evolution reactions(ORR/OER) are a key electrode process in the development of electrochemical energy conversion and storage devices,such as metal-air batteries and reversible fuel cells.The search for low-cost high-performance nanocarbon-based metal-free and non-precious metal bifunctional electrocatalysts for ORR/OER alternatives to the widely-used noble metal-based catalysts is a research focus.This review aims to outline the opportunities and available options for these nanocarbon-based bifunctional electrocatalysts.Through discussion of some current scientific issues,we summarize the development and breakthroughs of these electrocatalysts.Then we provide our perspectives on these issues and suggestions for some areas in the further work.We hope that this review can improve the interest in nanocarbon-based metal-free and non-precious metal bifunctional electrocatalysts for ORR/OER.展开更多
Metallic cobalt was deposited on acetylene black to synthesize a composite Co/C by chemical reduction method.A platinumfree electrocatalyst Co-N/C(800) for oxygen reduction reaction(ORR) was synthesized by mixing ...Metallic cobalt was deposited on acetylene black to synthesize a composite Co/C by chemical reduction method.A platinumfree electrocatalyst Co-N/C(800) for oxygen reduction reaction(ORR) was synthesized by mixing the composite Co/C with urea and heat-treating at 800℃.The results from linear sweep voltammograms indicated that the Co-N/C(800) is active to ORR.Theβ-Co and cobalt oxides are not the active site of the catalyst Co-N/C.However,the existence of cobalt facilitated the modification of nitrogen to carbon black and led to the formation of active site of catalyst Co-N/C(800).展开更多
Zn-air batteries(ZABs),especially the secondary batteries,have engrossed a great interest because of its high specific energy,economical and high safety.However,due to the insufficient activity and stability of bifunc...Zn-air batteries(ZABs),especially the secondary batteries,have engrossed a great interest because of its high specific energy,economical and high safety.However,due to the insufficient activity and stability of bifunctional electrocatalysts for air-cathode oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)processes,the practical application of rechargeable ZABs is seriously hindered.In the effort of developing high active,stable and cost-effective electrocatalysts,transition metal nitrides(TMNs)have been regarded as the candidates due to their high conductivity,strong corrosion-resistance,and bifunctional catalytic performance.In this paper,the research progress in TMNs-based material as ORR and OER electrocatalysts for ZABs is discussed with respect to their synthesis,chemical/physical characterization,and performance validation/optimization.The surface/interface nanoengineering strategies such as defect engineering,support binding,heteroatom introduction,crystal plane orientation,interface construction and small size effect,the physical and chemical properties of TMNs-based electrocatalysts are emphasized with respect to their structures/morphologies,composition,electrical conductivity,specific surface area,chemical stability and corrosion resistance.The challenges of TMNs-based materials as bifunctional air-cathode electrocatalysts in practical application are evaluated,and numerous research guidelines to solve these problems are put forward for facilitating further research and development.展开更多
The pyrolyzed carbon supported ferrum polypyrrole (Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid (TsOH), by a facile thermal annealing approach at desired temperature f...The pyrolyzed carbon supported ferrum polypyrrole (Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid (TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction (ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry (CV) and rotating disk electrode (RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of -1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C-Sn-C, an additional beneficial factor for the ORR.展开更多
Electrosynthesis of hydrogen peroxide(H2O2)is an on-site method that enables independent distribution applications in many fields due to its small-scale and sustainable features.The crucial point remains developing hi...Electrosynthesis of hydrogen peroxide(H2O2)is an on-site method that enables independent distribution applications in many fields due to its small-scale and sustainable features.The crucial point remains developing highly active,selective and cost-effective electrocatalysts.The electrosynthesis of H2O2 in acidic media is more practical owing to its stability and no need for further purification.We herein report a phosphorus and selenium tuning Co-based non-precious catalyst(CoPSe)toward two-electron oxygen reduction reaction(2e–ORR)to produce H2O2 in acidic media.The starting point of using both P and Se is finding a balance between strong ORR activity of CoSe and weak activity of CoP.The results demonstrated that the CoPSe catalyst exhibited the optimized 2e–ORR activity compared with CoP and CoSe.It disclosed an onset potential of 0.68 V and the H2O2 selectivity 76%-85%in a wide potential range(0–0.5 V).Notably,the CoPSe catalyst overcomes a significant challenge of a narrow-range selectivity for transitionmetal based 2e–ORR catalysts.Finally,combining with electro-Fenton reaction,an on-site system was constructed for efficient degradation of organic pollutants.This work provides a promising non-precious Co-based electrocatalyst for the electrosynthesis of H2O2 in acidic media.展开更多
Non-precious metal single-atom catalysts(NPM-SACs)with unique electronic structures and coordination environments have gained much attention in electrocatalysis owing to their low cost,high atomic utilization,and high...Non-precious metal single-atom catalysts(NPM-SACs)with unique electronic structures and coordination environments have gained much attention in electrocatalysis owing to their low cost,high atomic utilization,and high performance.NPM-SACs on carbon support(NPM-SACs/CS)are promising because of the carbon substrate with a large surface area,excellent electrical conductivity,and high chemical stability.This review provides an overview of recent developments in NPM-SACs/CS for the electrocatalytic field.First,the state-of-the-art synthesis methods and advanced characterization techniques of NPM-SACs/CS are discussed in detail.Then,the structural adjustment strategy of NPM-SACs/CS for optimizing electrocatalytic performance is introduced concisely.Furthermore,we provide a comprehensive summary of recent advances in developing NPM-SACs/CS for important electrochemical reactions,including carbon dioxide reduction reaction,hydrogen evolution reaction,oxygen evolution reaction,oxygen reduction reaction,and nitrogen reduction reaction.In the end,the existing challenges and future opportunities of NPM-SACs/CS in the electrocatalytic field are highlighted.展开更多
High cost has undoubtedly become the biggest obstacle to the commercialization of proton exchange membrane fuel cells(PEMFCs),in which Pt-based catalysts employed in the cathodic catalyst layer(CCL)account for the maj...High cost has undoubtedly become the biggest obstacle to the commercialization of proton exchange membrane fuel cells(PEMFCs),in which Pt-based catalysts employed in the cathodic catalyst layer(CCL)account for the major portion of the cost.Although nonprecious metal catalysts(NPMCs)show appreciable activity and stability in the oxygen reduction reaction(ORR),the performance of fuel cells based on NPMCs remains unsatisfactory compared to those using Pt-based CCL.Therefore,most studies on NPMC-based fuel cells focus on developing highly active catalysts rather than facilitating oxygen transport.In this work,the oxygen transport behavior in CCLs based on highly active Fe-N-C catalysts is comprehensively explored through the elaborate design of two types of membrane electrode structures,one containing low-Pt-based CCL and NPMCbased dummy catalyst layer(DCL)and the other containing only the NPMC-based CCL.Using Zn-N-C based DCLs of different thickness,the bulk oxygen transport resistance at the unit thickness in NPMC-based CCL was quantified via the limiting current method combined with linear fitting analysis.Then,the local and bulk resistances in NPMC-based CCLs were quantified via the limiting current method and scanning electron microscopy,respectively.Results show that the ratios of local and bulk oxygen transport resistances in NPMCbased CCL are 80%and 20%,respectively,and that an enhancement of local oxygen transport is critical to greatly improve the performance of NPMC-based PEMFCs.Furthermore,the activity of active sites per unit in NPMCbased CCLs was determined to be lower than that in the Pt-based CCL,thus explaining worse cell performance of NPMC-based membrane electrode assemblys(MEAs).It is believed that the development of NPMC-based PEMFCs should proceed not only through the design of catalysts with higher activity but also through the improvement of oxygen transport in the CCL.展开更多
Taking advantage of the nitrogen(N)-participation and large surface area of N-doped carbon nanocages(NCNCs),the Co Ox nanocrystals are conveniently immobilized onto the NCNCs with high dispersion.The Co Ox/NCNCs hybri...Taking advantage of the nitrogen(N)-participation and large surface area of N-doped carbon nanocages(NCNCs),the Co Ox nanocrystals are conveniently immobilized onto the NCNCs with high dispersion.The Co Ox/NCNCs hybrid exists in the mixed valence with predominant Co O over Co3O4 and demonstrates superb oxygen reduction reaction activity and stability remaining^94%current density even after operation over 100 h.These results suggest a promising strategy to develop advanced electrocatalysts with the novel NCNCs or even beyond.展开更多
Binuclear iron phthalocyanine/reduced graphene oxide(bi-Fe Pc/RGO) nanocomposite with good electrocatalytic activity for ORR in alkaline medium was prepared in one step. High angle annular dark field image scanning tr...Binuclear iron phthalocyanine/reduced graphene oxide(bi-Fe Pc/RGO) nanocomposite with good electrocatalytic activity for ORR in alkaline medium was prepared in one step. High angle annular dark field image scanning transmission electron microscopy(HAADF-STEM) and energy dispersive X-ray spectroscopy element mapping results show bi-Fe Pc was uniformly distributed on RGO. An obvious cathodic peak located at about-0.23 V(vs. SCE) in CV and an onset potential of-0.004 V(vs. SCE) in LSV indicate the as-prepared bi-Fe Pc/RGO nanocomposite possesses high activity which is closed to Pt/C for ORR. The ORR on bi-Fe Pc/RGO nanocomposite follows four-electron transfer pathway in alkaline medium. Compared with Pt/C, there is only a slight decrease(about 0.02 V vs. SCE) for bi-Fe Pc/RGO nanocomposite when the methanol exists. The excellent activity and methanol tolerance in alkaline solutions proves that bi-Fe Pc/RGO nanocomposite could be considered as a promising cathode catalyst for alkaline fuel cells.展开更多
We present a facile and versatile method for introducing various non-precious metal nanoparticles (NPs) in small nanotubes, such as single-walled carbon nanotubes (SWNTs), including 3d-metals (V, Mn, Fe and Co),...We present a facile and versatile method for introducing various non-precious metal nanoparticles (NPs) in small nanotubes, such as single-walled carbon nanotubes (SWNTs), including 3d-metals (V, Mn, Fe and Co), 4d-metals (Mo), and 5d-metals (W). This is realized by oxidizing encapsulated cycloalkene metal carbonyl complexes below their sublimation temperatures. This novel technique is significant because it avoids the diffusion and deposition of metal species on the outer walls of nanotubes, which has been challenging to achieve using the conventional filling methods. High-resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDX), Raman, and X-ray photoelectron spectroscopy (XPS) analyses revealed high filling efficiencies (〉 95% SWNTs filled with metal NPs). This method also provides a unique approach to fabricate highly dispersed and uniform SWNT-metal nanoparficle encapsulates with lower valence states, which are often not stable in the bulk.展开更多
A non-precious metal catalyst CoMe]C for the oxygen reduction reaction is prepared by heat-treating a mechanical mixture of carbon black, melamine and cobalt chloride at 600 under nitrogen atmosphere for 2 h. The cata...A non-precious metal catalyst CoMe]C for the oxygen reduction reaction is prepared by heat-treating a mechanical mixture of carbon black, melamine and cobalt chloride at 600 under nitrogen atmosphere for 2 h. The catalytic activity of CoMe/C is characterized by the electrochemical linear sweep voltammetry technique. The onset reduction potential of the catalyst is 0.55 V (vs. SCE) at a scanning rate of 5 mV/s in 0.5 mol/L H2SO4 solution. The formation of the ORR activity sites of CoMe/C is facilitated by metallic β- cobalt.展开更多
The development of highly efficient catalysts for cathodes remains an important objective of fuel cell research. Here, we report Co3O4 nanoparticles assembled on a polypyrrole/graphene oxide electrocatalyst (C...The development of highly efficient catalysts for cathodes remains an important objective of fuel cell research. Here, we report Co3O4 nanoparticles assembled on a polypyrrole/graphene oxide electrocatalyst (Co3O4/Ppy/GO) as an efficient catalyst for the oxygen reduction reaction (ORR) in alkaline media. The catalyst was prepared via the hydrothermal reaction of Co2+ ions with Ppy-modified GO. The GO, Ppy/GO, and Co3O4/Ppy/GO were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The incorporation of Ppy into GO nanosheets resulted in the formation of a nitrogen-modified GO po-rous structure, which acted as an efficient electron-transport network for the ORR. With further anchoring of Co3O4 on Ppy/GO, the as-prepared Co3O4/Ppy/GO exhibited excellent ORR activity and followed a four-electron route mechanism for the ORR in alkaline solution. An onset potential of -0.10 V vs. a saturated calomel electrode and a diffusion limiting current density of 2.30 mA/cm^2 were achieved for the Co3O4/Ppy/GO catalyst heated at 800 ℃; these values are comparable to those for noble-metal-based Pt/C catalysts. Our work demonstrates that Co3O4/Ppy/GO is highly active for the ORR. Notably, the Ppy coupling effects between Co3O4 and GO provide a new route for the preparation of efficient non-precious electrocatalysts with hierarchical porous structures for fuel cell applications.展开更多
A non-precious metal catalyst MnHMTA/C to oxygen reduction reaction was prepared by py- rolyzing a precursor from manganese chloride, hexamethylenetetramine and acetylene black in nitrogen gas atmosphere. The effect o...A non-precious metal catalyst MnHMTA/C to oxygen reduction reaction was prepared by py- rolyzing a precursor from manganese chloride, hexamethylenetetramine and acetylene black in nitrogen gas atmosphere. The effect of heat treatment temperature and flowing of nitrogen gas were investigated. A catalyst with the highest activity can be obtained at 700 ℃. Mn(Ⅱ) ion was changed to MnO in heat treatment, which improved the catalytic activity of the catalyst. Hexamethylenetetramine takes part in the formation of active site of the catalyst as its decomposed gases. The flowing of protective gas takes the decomposed gases out of the tube furnace and brings negative effect on the catalytic activity of the MnHMTA/C catalyst.展开更多
The stabilization of non-precious metals as isolated active sites with high loading density over nitrogendoped carbon materials is essential for realizing the industrial application of single atom catalysts.However,ac...The stabilization of non-precious metals as isolated active sites with high loading density over nitrogendoped carbon materials is essential for realizing the industrial application of single atom catalysts.However,achieving high loading of single cobalt active sites with greatly enhanced oxygen reduction reaction(ORR)activity and stability remains challenging.Here,an efficient approach was described to create a single atom cobalt electrocatalyst(Co SAs/NC)which possesses enhanced mesoporosity and specific surface area that greatly favor the mass transportation and exposure of accessible active sites.The electronic structure of the catalyst by the strong metal-support interaction has been elucidated through experimental characterizations and theoretical calculations.Due to dramatically enhanced mass transport and electron transfer endowed by morphology and electronic structure engineering,Co SAs/NC exhibits remarkable ORR performance with excellent activity(onset and half-wave potentials of 1.04 V(RHE)and 0.90 V(RHE),Tafel slope of 69.8 mV dec^(-1)and J_(k) of 18.8 mA cm^(-2)at 0.85 V)and stability(7 mV activity decay after 10,000 cycles).In additio n,the catalyst demonstrates great promise as an alternative to traditional Pt/C catalyst in zinc-air batteries while maintaining high performance in terms of high specific capacity of(796.1 mAh/g_(Zn)),power density(175.4 mW/cm^(2)),and long-term cycling stability(140 h).This study presents a facile approach to design SACs with highly accessible active sites for electrochemical transformations.展开更多
Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication ...Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication of a bifunctional oxygen electrocatalyst has been proposed.The efficient non-preciousmetal-based electrocatalyst,Fe/Fe_(3)C@Fe-N_(x)-C consists of highly curved onion-like carbon shells that encapsulate Fe/Fe_(3)C nanoparticles,distributed on an extensively porous graphitic carbon aerogel.The obtained Fe/Fe_(3)C@Fe-N_(x)-C aerogel exhibited superb electrochemical activity,excellent durability,and high methanol tolerance.The experimental results indicated that the assembly of onion-like carbon shells with encapsulated Fe/Fe_(3)C yielded highly curved carbon surfaces with abundant Fe-Nxactive sites,a porous structure,and enhanced electrocatalytic activity towards ORR and OER,hence displaying promising potential for application as an air cathode in rechargeable Zn-air batteries.The constructed Zn-air battery possessed an exceptional peak power density of~147 mW cm^(-2),outstanding cycling stability(200 cycles,1 h per cycle),and a small voltage gap of 0.87 V.This study offers valuable insights regarding the construction of low-cost and highly active bifunctional oxygen electrocatalysts for efficient air batteries.展开更多
Understanding of the oxygen reduction reaction(ORR)mechanism for single atom catalysts is pivotal for the rational design of non-precious metal cathode materials and the commercialization of fuel cells.Herein,a series...Understanding of the oxygen reduction reaction(ORR)mechanism for single atom catalysts is pivotal for the rational design of non-precious metal cathode materials and the commercialization of fuel cells.Herein,a series of non-precious metal electrocatalysts based on nitrogen-doped bimetallic(Fe and Co)carbide were modeled by density functional theory calculations to predict the corresponding reaction pathways.The study elucidated prior oxygen adsorption on the Fe atom in the dual site and the modifier role of Co atoms to tune the electronic structures of Fe.The reaction activity was highly correlated with the bimetallic center and the coordination environment of the adjacent nitrogen.Interestingly,the preadsorption of*OH resulted in the apparent change of metal atoms'electronic states with the d-band center shifting toward the Fermi level,thereby boosting reaction activity.The result should help promote the fundamental understanding of active sites in ORR catalysts and provide an effective approach to the design of highly efficient ORR catalysts on an atomic scale.展开更多
One of the major challenges associated with fuel cells is the design of highly efficient electrocatalysts to reduce the high overpotential of the oxygen reduction reaction (ORR). Here we report Polyaniline (PANI) base...One of the major challenges associated with fuel cells is the design of highly efficient electrocatalysts to reduce the high overpotential of the oxygen reduction reaction (ORR). Here we report Polyaniline (PANI) based micro/nanomaterials with or without transition metals, prepared by the emulsion polymerization and subsequent heat treatment. PANI microspheres with the diameter of about 0.7 mu m have been prepared in basic (NH3 solution) condition, using two different types of surfactant (CTAB, SDS) as the stabilizer, ammonium persulphate (APS) as oxidant with aniline/surfactants molar ratio at 1/1 under the hydrothermal treatment. PANI nanorods, Fe-PANI, and Fe-Co-PANI have been synthesized in acidic (HCI) medium with aniline/surfactants molar ratio at 1/2 and polymerization carried out without stirring for 24 h. Products mainly Fe-Co-PANI have shown high current density with increasing sweep rate and excellent specific capacitance 1753 F/g at the scan rate of 1 mV/s. Additionally, it has shown high thermal stability by thermogravimetric analysis (TGA). Fe-PANI has been investigated for excellent performance toward ORR with four electron selectivity in the basic electrolyte. The PANI-based catalysts from emulsion polymerization demonstrate that the method is valuable for making non-precious metal heterogeneous electrocatalysts for ORR or energy storage and conversion technology. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.展开更多
Due to larger atom utilization,unique electronic properties and unsaturated coordination,atomically dispersed non-precious metal catalysts with outstanding performances have received great attention in electrocatalysi...Due to larger atom utilization,unique electronic properties and unsaturated coordination,atomically dispersed non-precious metal catalysts with outstanding performances have received great attention in electrocatalysis.Considering the challenge of serious aggregation,rational synthesis of an atomic catalyst with good dispersion of atoms is paramount to the development of these catalysts.Herein,we report an enhanced confinement strategy to synthesize a catalyst comprised of atomically dispersed Fe supported on porous nitrogen-doped graphitic carbon from the novel and more cross-linkable Melamine-Glyoxal Resin.Densified isolated grid trapping,excessive melamine restricting,and nitrogen anchoring are strongly combined to ensure the final atomic-level dispersion of metal atoms.Experimental studies revealed enhanced kinetics of the obtained catalyst towards oxygen reduction reaction(ORR).This catalytic activity originates from the highly active surface with atomically dispersed iron sites as well as the multi-level three-dimensional structure with fast mass and electron transfer.The enhanced confinement strategy endows the resin-derived atomic catalyst with a great prospect to develop for commercialization in future.展开更多
The incorporation of Pt into an iron-nitrogen-carbon(Fe NC)catalyst for the oxygen reduction reaction(ORR)was recently shown to enhance catalyst stability without Pt directly contributing to the ORR activity.However,t...The incorporation of Pt into an iron-nitrogen-carbon(Fe NC)catalyst for the oxygen reduction reaction(ORR)was recently shown to enhance catalyst stability without Pt directly contributing to the ORR activity.However,the mechanistic origin of this stabilisation remained obscure.It is established herein with rotating ring disc experiments that the side product,H_(2)O_(2),which is known to damage FeNC catalysts,is suppressed by the presence of Pt.The formation of reactive oxygen species is additionally inhibited,independent of intrinsic H_(2)O_(2) formation,as determined by electron paramagnetic resonance.Transmission electron microscopy identifies an oxidised Fe-rich layer covering the Pt particles,thus explaining the inactivity of the latter towards the ORR.These insights develop understanding of Fe NC degradation mechanisms during ORR catalysis,and crucially establish the required properties of a precious metal free protective catalyst to improve Fe NC stability in acidic media.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(DUT15RC(3)001,DUT15ZD225)the Program for Liao-ning Excellent Talents in University(LR2015014)+1 种基金the Liaoning BaiQianWan Talents Program(201519)Dalian Excellent Young Scientific and Technological Talents(2015R006)
文摘Significant progress has been made in the development of non-precious metal electrocatalysts (NPMEs) during the past decade. Correspondingly, there is an urgent demand for an appropriate measurement method to be established for the reliable evaluation of NPMEs. In this study, platinum and graphite counter electrodes were used to investigate the impact of counter electrode material on the accelerated durability testing (ADT) of NPMEs in acidic medium. Platinum used as the coun- ter electrode in a traditional three-electrode electrochemical cell was found to dissolve in acidic medium and re-deposit on NPME coated on the working electrode during ADT. Such re-deposition causes the oxygen reduction reaction (ORR) performance of NPMEs to remarkably improve, and thus will seriously mislead our judgment of NPMEs if we are unaware of it. The phenomenon can be avoided using a graphite counter electrode.
基金the financial support provided by the National Natural Science Foundation of China(Grant Nos.51932005 and 21773269)the Joint Research Fund LiaoningShenyang National Laboratory for Materials Science(Grant No.20180510047)Liao Ning Revitalization Talents Program(XLYC1807175)。
文摘The oxygen reduction/evolution reactions(ORR/OER) are a key electrode process in the development of electrochemical energy conversion and storage devices,such as metal-air batteries and reversible fuel cells.The search for low-cost high-performance nanocarbon-based metal-free and non-precious metal bifunctional electrocatalysts for ORR/OER alternatives to the widely-used noble metal-based catalysts is a research focus.This review aims to outline the opportunities and available options for these nanocarbon-based bifunctional electrocatalysts.Through discussion of some current scientific issues,we summarize the development and breakthroughs of these electrocatalysts.Then we provide our perspectives on these issues and suggestions for some areas in the further work.We hope that this review can improve the interest in nanocarbon-based metal-free and non-precious metal bifunctional electrocatalysts for ORR/OER.
基金funded by the Third Stage Training of"211 Project"(No.S-09103) of ChinaNatural Science Foundation Project of Chongqing(No.CSTC2009BB6213)
文摘Metallic cobalt was deposited on acetylene black to synthesize a composite Co/C by chemical reduction method.A platinumfree electrocatalyst Co-N/C(800) for oxygen reduction reaction(ORR) was synthesized by mixing the composite Co/C with urea and heat-treating at 800℃.The results from linear sweep voltammograms indicated that the Co-N/C(800) is active to ORR.Theβ-Co and cobalt oxides are not the active site of the catalyst Co-N/C.However,the existence of cobalt facilitated the modification of nitrogen to carbon black and led to the formation of active site of catalyst Co-N/C(800).
基金financial support from the National Key Research and Development Program of China(2017YFB0102900)
文摘Zn-air batteries(ZABs),especially the secondary batteries,have engrossed a great interest because of its high specific energy,economical and high safety.However,due to the insufficient activity and stability of bifunctional electrocatalysts for air-cathode oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)processes,the practical application of rechargeable ZABs is seriously hindered.In the effort of developing high active,stable and cost-effective electrocatalysts,transition metal nitrides(TMNs)have been regarded as the candidates due to their high conductivity,strong corrosion-resistance,and bifunctional catalytic performance.In this paper,the research progress in TMNs-based material as ORR and OER electrocatalysts for ZABs is discussed with respect to their synthesis,chemical/physical characterization,and performance validation/optimization.The surface/interface nanoengineering strategies such as defect engineering,support binding,heteroatom introduction,crystal plane orientation,interface construction and small size effect,the physical and chemical properties of TMNs-based electrocatalysts are emphasized with respect to their structures/morphologies,composition,electrical conductivity,specific surface area,chemical stability and corrosion resistance.The challenges of TMNs-based materials as bifunctional air-cathode electrocatalysts in practical application are evaluated,and numerous research guidelines to solve these problems are put forward for facilitating further research and development.
基金supported by the National Natural Science Foundation of China(91223202)the International Science&Technology Cooperation Program of China(No.2011DFA73410)+1 种基金Tsinghua University Initiative Scientific Research Program(No.20101081907)the National Key Basic Research Program of China-973 Program(No.2011CB013102)
文摘The pyrolyzed carbon supported ferrum polypyrrole (Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid (TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction (ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry (CV) and rotating disk electrode (RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of -1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C-Sn-C, an additional beneficial factor for the ORR.
基金the National Natural Science Foundation of China(Nos.21805052,21974031,2278092)Science and Technology Research Project of Guangzhou(Nos.202102020787 and 202201000002)+2 种基金Department of Science&Technology of Guangdong Province(No.2022A156)Key Discipline of Materials Science and Engineering,Bureau of Education of Guangzhou(No.20225546)the Innovation&Entrepreneurship for the College Students of Guangzhou University(No.XJ202111078175).
文摘Electrosynthesis of hydrogen peroxide(H2O2)is an on-site method that enables independent distribution applications in many fields due to its small-scale and sustainable features.The crucial point remains developing highly active,selective and cost-effective electrocatalysts.The electrosynthesis of H2O2 in acidic media is more practical owing to its stability and no need for further purification.We herein report a phosphorus and selenium tuning Co-based non-precious catalyst(CoPSe)toward two-electron oxygen reduction reaction(2e–ORR)to produce H2O2 in acidic media.The starting point of using both P and Se is finding a balance between strong ORR activity of CoSe and weak activity of CoP.The results demonstrated that the CoPSe catalyst exhibited the optimized 2e–ORR activity compared with CoP and CoSe.It disclosed an onset potential of 0.68 V and the H2O2 selectivity 76%-85%in a wide potential range(0–0.5 V).Notably,the CoPSe catalyst overcomes a significant challenge of a narrow-range selectivity for transitionmetal based 2e–ORR catalysts.Finally,combining with electro-Fenton reaction,an on-site system was constructed for efficient degradation of organic pollutants.This work provides a promising non-precious Co-based electrocatalyst for the electrosynthesis of H2O2 in acidic media.
基金support from the China Postdoctoral Science Foundation(2022M711553).Y.W.would like to acknowledge the support from the National Natural Science Foundation of China(22171132)the Innovation Fund from Nanjing University(020514913419)+5 种基金the Program for Innovative Talents and Entrepreneurs in Jiangsu(020513006012 and 020513006014),and the National Key R&D Program of China(2002YFB3607000).W.Z.would like to acknowledge the support from the National Natural Science Foundation of China(22176086)Natural Science Foundation of Jiangsu Province(BK20210189)State Key Laboratory of Pollution Control and Resource Reuse(PCRR-ZZ-202106)the Fundamental Research Funds for the Central Universities(021114380183,021114380189 and 021114380199)the Research Funds from the Nanjing Science and Technology Innovation Project for Chinese Scholars Studying Abroad(13006003)the Research Funds from Frontiers Science Center for Critical Earth Material Cycling of Nanjing University,and Research Funds for Jiangsu Distinguished Professor.Y.L.would like to thank the support from the Washington State University startup fund.
文摘Non-precious metal single-atom catalysts(NPM-SACs)with unique electronic structures and coordination environments have gained much attention in electrocatalysis owing to their low cost,high atomic utilization,and high performance.NPM-SACs on carbon support(NPM-SACs/CS)are promising because of the carbon substrate with a large surface area,excellent electrical conductivity,and high chemical stability.This review provides an overview of recent developments in NPM-SACs/CS for the electrocatalytic field.First,the state-of-the-art synthesis methods and advanced characterization techniques of NPM-SACs/CS are discussed in detail.Then,the structural adjustment strategy of NPM-SACs/CS for optimizing electrocatalytic performance is introduced concisely.Furthermore,we provide a comprehensive summary of recent advances in developing NPM-SACs/CS for important electrochemical reactions,including carbon dioxide reduction reaction,hydrogen evolution reaction,oxygen evolution reaction,oxygen reduction reaction,and nitrogen reduction reaction.In the end,the existing challenges and future opportunities of NPM-SACs/CS in the electrocatalytic field are highlighted.
基金the National Key R&D Program of China(Grant No.2021YFB4001303)the National Natural Science Foundation of China(Grant No.21975157)。
文摘High cost has undoubtedly become the biggest obstacle to the commercialization of proton exchange membrane fuel cells(PEMFCs),in which Pt-based catalysts employed in the cathodic catalyst layer(CCL)account for the major portion of the cost.Although nonprecious metal catalysts(NPMCs)show appreciable activity and stability in the oxygen reduction reaction(ORR),the performance of fuel cells based on NPMCs remains unsatisfactory compared to those using Pt-based CCL.Therefore,most studies on NPMC-based fuel cells focus on developing highly active catalysts rather than facilitating oxygen transport.In this work,the oxygen transport behavior in CCLs based on highly active Fe-N-C catalysts is comprehensively explored through the elaborate design of two types of membrane electrode structures,one containing low-Pt-based CCL and NPMCbased dummy catalyst layer(DCL)and the other containing only the NPMC-based CCL.Using Zn-N-C based DCLs of different thickness,the bulk oxygen transport resistance at the unit thickness in NPMC-based CCL was quantified via the limiting current method combined with linear fitting analysis.Then,the local and bulk resistances in NPMC-based CCLs were quantified via the limiting current method and scanning electron microscopy,respectively.Results show that the ratios of local and bulk oxygen transport resistances in NPMCbased CCL are 80%and 20%,respectively,and that an enhancement of local oxygen transport is critical to greatly improve the performance of NPMC-based PEMFCs.Furthermore,the activity of active sites per unit in NPMCbased CCLs was determined to be lower than that in the Pt-based CCL,thus explaining worse cell performance of NPMC-based membrane electrode assemblys(MEAs).It is believed that the development of NPMC-based PEMFCs should proceed not only through the design of catalysts with higher activity but also through the improvement of oxygen transport in the CCL.
基金supported by the National Natural Science Foundation of China(51232003,21473089,21373108,21173115)the National Basic Research Program of China(2013CB932902)+2 种基金Jiangsu Province Science and Technology Support Project(BE2012159)Suzhou Science and Technology Plan projects(ZXG2013025)National Science Fund for Talent Training in Basic Science(J1103310)
文摘Taking advantage of the nitrogen(N)-participation and large surface area of N-doped carbon nanocages(NCNCs),the Co Ox nanocrystals are conveniently immobilized onto the NCNCs with high dispersion.The Co Ox/NCNCs hybrid exists in the mixed valence with predominant Co O over Co3O4 and demonstrates superb oxygen reduction reaction activity and stability remaining^94%current density even after operation over 100 h.These results suggest a promising strategy to develop advanced electrocatalysts with the novel NCNCs or even beyond.
基金supported by the National Natural Science Foundation of China (21275014, 21375005)the Excellent Young Scientists Fund of NSFC (21322501)+2 种基金the Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions (CIT& TCD20140309)the Program for New Century Excellent Talents in University (NCET-12-0603)the Beijing Natural Science Foundation Program and Scientific Research Key Program of the Beijing Municipal Commission of Education (KZ201310005001)
文摘Binuclear iron phthalocyanine/reduced graphene oxide(bi-Fe Pc/RGO) nanocomposite with good electrocatalytic activity for ORR in alkaline medium was prepared in one step. High angle annular dark field image scanning transmission electron microscopy(HAADF-STEM) and energy dispersive X-ray spectroscopy element mapping results show bi-Fe Pc was uniformly distributed on RGO. An obvious cathodic peak located at about-0.23 V(vs. SCE) in CV and an onset potential of-0.004 V(vs. SCE) in LSV indicate the as-prepared bi-Fe Pc/RGO nanocomposite possesses high activity which is closed to Pt/C for ORR. The ORR on bi-Fe Pc/RGO nanocomposite follows four-electron transfer pathway in alkaline medium. Compared with Pt/C, there is only a slight decrease(about 0.02 V vs. SCE) for bi-Fe Pc/RGO nanocomposite when the methanol exists. The excellent activity and methanol tolerance in alkaline solutions proves that bi-Fe Pc/RGO nanocomposite could be considered as a promising cathode catalyst for alkaline fuel cells.
文摘We present a facile and versatile method for introducing various non-precious metal nanoparticles (NPs) in small nanotubes, such as single-walled carbon nanotubes (SWNTs), including 3d-metals (V, Mn, Fe and Co), 4d-metals (Mo), and 5d-metals (W). This is realized by oxidizing encapsulated cycloalkene metal carbonyl complexes below their sublimation temperatures. This novel technique is significant because it avoids the diffusion and deposition of metal species on the outer walls of nanotubes, which has been challenging to achieve using the conventional filling methods. High-resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDX), Raman, and X-ray photoelectron spectroscopy (XPS) analyses revealed high filling efficiencies (〉 95% SWNTs filled with metal NPs). This method also provides a unique approach to fabricate highly dispersed and uniform SWNT-metal nanoparficle encapsulates with lower valence states, which are often not stable in the bulk.
基金supported by the Fundamental Research Funds for the Central Universities (No. CDJXS12220002)the Specialized Research Fund for the Doctoral Program of Sichuan University of Science and Engineering (No. 2012RC16)+2 种基金the Opening Project of Key Laboratory of Green Catalysis of Sichuan Institutes of High Education (No. LYJ1206)the National Undergraduate Innovation Training Project (No. 1110611046)Discipline Construction Project of Sichuan University of Science and Engineering
文摘A non-precious metal catalyst CoMe]C for the oxygen reduction reaction is prepared by heat-treating a mechanical mixture of carbon black, melamine and cobalt chloride at 600 under nitrogen atmosphere for 2 h. The catalytic activity of CoMe/C is characterized by the electrochemical linear sweep voltammetry technique. The onset reduction potential of the catalyst is 0.55 V (vs. SCE) at a scanning rate of 5 mV/s in 0.5 mol/L H2SO4 solution. The formation of the ORR activity sites of CoMe/C is facilitated by metallic β- cobalt.
基金supported by the National Natural Science Foundation of China(21373042)~~
文摘The development of highly efficient catalysts for cathodes remains an important objective of fuel cell research. Here, we report Co3O4 nanoparticles assembled on a polypyrrole/graphene oxide electrocatalyst (Co3O4/Ppy/GO) as an efficient catalyst for the oxygen reduction reaction (ORR) in alkaline media. The catalyst was prepared via the hydrothermal reaction of Co2+ ions with Ppy-modified GO. The GO, Ppy/GO, and Co3O4/Ppy/GO were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The incorporation of Ppy into GO nanosheets resulted in the formation of a nitrogen-modified GO po-rous structure, which acted as an efficient electron-transport network for the ORR. With further anchoring of Co3O4 on Ppy/GO, the as-prepared Co3O4/Ppy/GO exhibited excellent ORR activity and followed a four-electron route mechanism for the ORR in alkaline solution. An onset potential of -0.10 V vs. a saturated calomel electrode and a diffusion limiting current density of 2.30 mA/cm^2 were achieved for the Co3O4/Ppy/GO catalyst heated at 800 ℃; these values are comparable to those for noble-metal-based Pt/C catalysts. Our work demonstrates that Co3O4/Ppy/GO is highly active for the ORR. Notably, the Ppy coupling effects between Co3O4 and GO provide a new route for the preparation of efficient non-precious electrocatalysts with hierarchical porous structures for fuel cell applications.
文摘A non-precious metal catalyst MnHMTA/C to oxygen reduction reaction was prepared by py- rolyzing a precursor from manganese chloride, hexamethylenetetramine and acetylene black in nitrogen gas atmosphere. The effect of heat treatment temperature and flowing of nitrogen gas were investigated. A catalyst with the highest activity can be obtained at 700 ℃. Mn(Ⅱ) ion was changed to MnO in heat treatment, which improved the catalytic activity of the catalyst. Hexamethylenetetramine takes part in the formation of active site of the catalyst as its decomposed gases. The flowing of protective gas takes the decomposed gases out of the tube furnace and brings negative effect on the catalytic activity of the MnHMTA/C catalyst.
基金supported by the Postdoctoral Research Foundation of China(2019M661247,2020T130091)Scientific Research Foundation for Returned Scholars of Heilongjiang Province of China(719900091)+1 种基金Program for Overseas Talents Introduction of Northeast Petroleum University(15041260303)Heilongjiang Touyan Innovation Team Program。
文摘The stabilization of non-precious metals as isolated active sites with high loading density over nitrogendoped carbon materials is essential for realizing the industrial application of single atom catalysts.However,achieving high loading of single cobalt active sites with greatly enhanced oxygen reduction reaction(ORR)activity and stability remains challenging.Here,an efficient approach was described to create a single atom cobalt electrocatalyst(Co SAs/NC)which possesses enhanced mesoporosity and specific surface area that greatly favor the mass transportation and exposure of accessible active sites.The electronic structure of the catalyst by the strong metal-support interaction has been elucidated through experimental characterizations and theoretical calculations.Due to dramatically enhanced mass transport and electron transfer endowed by morphology and electronic structure engineering,Co SAs/NC exhibits remarkable ORR performance with excellent activity(onset and half-wave potentials of 1.04 V(RHE)and 0.90 V(RHE),Tafel slope of 69.8 mV dec^(-1)and J_(k) of 18.8 mA cm^(-2)at 0.85 V)and stability(7 mV activity decay after 10,000 cycles).In additio n,the catalyst demonstrates great promise as an alternative to traditional Pt/C catalyst in zinc-air batteries while maintaining high performance in terms of high specific capacity of(796.1 mAh/g_(Zn)),power density(175.4 mW/cm^(2)),and long-term cycling stability(140 h).This study presents a facile approach to design SACs with highly accessible active sites for electrochemical transformations.
基金supported financially by the National Natural Science Foundation of China,China(Grant No.51702180,51572136,91963113,21703116,51372127,51873096)The Scientific and Technical Development Project of Qingdao,China(Grant No.18-2-2-52-jch)+1 种基金The Taishan Scholar Advantage and Characteristic Discipline Team of Eco Chemical Process and TechnologyThe Natural Science Foundation of Hebei Province(B2019204009)。
文摘Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication of a bifunctional oxygen electrocatalyst has been proposed.The efficient non-preciousmetal-based electrocatalyst,Fe/Fe_(3)C@Fe-N_(x)-C consists of highly curved onion-like carbon shells that encapsulate Fe/Fe_(3)C nanoparticles,distributed on an extensively porous graphitic carbon aerogel.The obtained Fe/Fe_(3)C@Fe-N_(x)-C aerogel exhibited superb electrochemical activity,excellent durability,and high methanol tolerance.The experimental results indicated that the assembly of onion-like carbon shells with encapsulated Fe/Fe_(3)C yielded highly curved carbon surfaces with abundant Fe-Nxactive sites,a porous structure,and enhanced electrocatalytic activity towards ORR and OER,hence displaying promising potential for application as an air cathode in rechargeable Zn-air batteries.The constructed Zn-air battery possessed an exceptional peak power density of~147 mW cm^(-2),outstanding cycling stability(200 cycles,1 h per cycle),and a small voltage gap of 0.87 V.This study offers valuable insights regarding the construction of low-cost and highly active bifunctional oxygen electrocatalysts for efficient air batteries.
基金the Joint Fund of the National Natural Science Foundation of China(U1732267).
文摘Understanding of the oxygen reduction reaction(ORR)mechanism for single atom catalysts is pivotal for the rational design of non-precious metal cathode materials and the commercialization of fuel cells.Herein,a series of non-precious metal electrocatalysts based on nitrogen-doped bimetallic(Fe and Co)carbide were modeled by density functional theory calculations to predict the corresponding reaction pathways.The study elucidated prior oxygen adsorption on the Fe atom in the dual site and the modifier role of Co atoms to tune the electronic structures of Fe.The reaction activity was highly correlated with the bimetallic center and the coordination environment of the adjacent nitrogen.Interestingly,the preadsorption of*OH resulted in the apparent change of metal atoms'electronic states with the d-band center shifting toward the Fermi level,thereby boosting reaction activity.The result should help promote the fundamental understanding of active sites in ORR catalysts and provide an effective approach to the design of highly efficient ORR catalysts on an atomic scale.
基金support by the National Natural Science Foundation of China(Grant no.21373042)
文摘One of the major challenges associated with fuel cells is the design of highly efficient electrocatalysts to reduce the high overpotential of the oxygen reduction reaction (ORR). Here we report Polyaniline (PANI) based micro/nanomaterials with or without transition metals, prepared by the emulsion polymerization and subsequent heat treatment. PANI microspheres with the diameter of about 0.7 mu m have been prepared in basic (NH3 solution) condition, using two different types of surfactant (CTAB, SDS) as the stabilizer, ammonium persulphate (APS) as oxidant with aniline/surfactants molar ratio at 1/1 under the hydrothermal treatment. PANI nanorods, Fe-PANI, and Fe-Co-PANI have been synthesized in acidic (HCI) medium with aniline/surfactants molar ratio at 1/2 and polymerization carried out without stirring for 24 h. Products mainly Fe-Co-PANI have shown high current density with increasing sweep rate and excellent specific capacitance 1753 F/g at the scan rate of 1 mV/s. Additionally, it has shown high thermal stability by thermogravimetric analysis (TGA). Fe-PANI has been investigated for excellent performance toward ORR with four electron selectivity in the basic electrolyte. The PANI-based catalysts from emulsion polymerization demonstrate that the method is valuable for making non-precious metal heterogeneous electrocatalysts for ORR or energy storage and conversion technology. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
基金financially supported by the Hebei Province Natural Science Foundation Innovation Group Project(B2021203016)the National Natural Science Foundation of China(51674221 and 51704261)+1 种基金the Provincial Graduate Innovation Assistant Project of Yanshan University(023000309)partially supported by the ARC Future Fellowship(FT180100705)of Australia。
文摘Due to larger atom utilization,unique electronic properties and unsaturated coordination,atomically dispersed non-precious metal catalysts with outstanding performances have received great attention in electrocatalysis.Considering the challenge of serious aggregation,rational synthesis of an atomic catalyst with good dispersion of atoms is paramount to the development of these catalysts.Herein,we report an enhanced confinement strategy to synthesize a catalyst comprised of atomically dispersed Fe supported on porous nitrogen-doped graphitic carbon from the novel and more cross-linkable Melamine-Glyoxal Resin.Densified isolated grid trapping,excessive melamine restricting,and nitrogen anchoring are strongly combined to ensure the final atomic-level dispersion of metal atoms.Experimental studies revealed enhanced kinetics of the obtained catalyst towards oxygen reduction reaction(ORR).This catalytic activity originates from the highly active surface with atomically dispersed iron sites as well as the multi-level three-dimensional structure with fast mass and electron transfer.The enhanced confinement strategy endows the resin-derived atomic catalyst with a great prospect to develop for commercialization in future.
基金a fellowship from the Alexander von Humboldt foundation。
文摘The incorporation of Pt into an iron-nitrogen-carbon(Fe NC)catalyst for the oxygen reduction reaction(ORR)was recently shown to enhance catalyst stability without Pt directly contributing to the ORR activity.However,the mechanistic origin of this stabilisation remained obscure.It is established herein with rotating ring disc experiments that the side product,H_(2)O_(2),which is known to damage FeNC catalysts,is suppressed by the presence of Pt.The formation of reactive oxygen species is additionally inhibited,independent of intrinsic H_(2)O_(2) formation,as determined by electron paramagnetic resonance.Transmission electron microscopy identifies an oxidised Fe-rich layer covering the Pt particles,thus explaining the inactivity of the latter towards the ORR.These insights develop understanding of Fe NC degradation mechanisms during ORR catalysis,and crucially establish the required properties of a precious metal free protective catalyst to improve Fe NC stability in acidic media.