Atomically dispersed Mn-Nx catalysts derived from Mn-hexamine coordination frameworks for oxygen reduction reaction

Metal-organic frameworks recently have been burgeoning and used as precursors to obtain various metal-nitrogen-carbon catalysts for oxygen reduction reaction(ORR).Although rarely studied,Mn-N-C is a promising catalyst for ORR due to its weak Fenton reaction activity and strong graphitization catalysis.Here,we developed a facile strategy for anchoring the atomically dispersed nitrogen-coordinated single Mn sites on carbon nanosheets(MnNCS)from an Mn-hexamine coordination framework.The atomically dispersed Mn-N4 sites were dispersed on ultrathin carbon nanosheets with a hierarchically porous structure.The optimized MnNCS displayed an excellent ORR performance in half-cells(0.89 V vs.reversible hydrogen electrode(RHE)in base and 0.76 V vs.RHE in acid in half-wave potential)and Zn-air batteries(233 mW cm^(−2)in peak power density),along with significantly enhanced stability.Density functional theory calculations further corroborated that the Mn-N4-C1_(2)site has favorable adsorption of*OH as the rate-determining step.These findings demonstrate that the metal-hexamine coordination framework can be used as a model system for the rational design of highly active atomic metal catalysts for energy applications.

Fe-N-C core-shell catalysts with single low-spin Fe(Ⅱ)-N_(4)species for oxygen reduction reaction and high-performance proton exchange membrane fuel cells

Fe-N-doped carbon materials(Fe-N-C)are promising candidates for oxygen reduction reaction(ORR)relative to Pt-based catalysts in proton exchange membrane fuel cells(PEMFCs).However,the intrinsic contributions of Fe-N_(4)moiety with different chemical/spin states(e.g.D1,D2,D3)to ORR are unclear since various states coexist inevitably.In the present work,Fe-N-C core-shell nanocatalyst with single lowspin Fe(Ⅱ)-N_(4)species(D1)is synthesized and identified with ex-situ ultralow temperature Mossbauer spectroscopy(T=1.6 K)that could essentially differentiate various Fe-N_(4)states and invisible Fe-O species.By quantifying with CO-pulse chemisorption,site density and turnover frequency of Fe-N-C catalysts reach 2.4×10^(-9)site g^(-1)and 23 e site~(-1)s^(-1)during the ORR,respectively.Half-wave potential(0.915V_(RHE))of the Fe-N-C catalyst is more positive(approximately 54 mV)than that of Pt/C.Moreover,we observe that the performance of PEMFCs on Fe-N-C almost achieves the 2025 target of the US Department of Energy by demonstrating a current density of 1.037 A cm^(-2)combined with the peak power density of 0,685 W cm^(-2),suggesting the critical role of Fe(Ⅱ)-N_(4)site(D1).After 500 h of running,PEMFCs still deliver a power density of 1.26 W cm^(-2)at 1.0 bar H_(2)-O_(2),An unexpected rate-determining step is figured out by isotopic labelling experiment and theoretical calculation.This work not only offers valuable insights regarding the intrinsic contribution of Fe-N_(4)with a single spin state to alkaline/acidic ORR,but also provides great opportunities for developing high-performance stable PEMFCs.

Rational design of vitamin C/defective carbon van der Waals heterostructure for enhanced activity,durability and storage stability toward oxygen reduction reaction

Metal-free defective carbon materials with abundant active sites have been widely studied as low-cost and efficient oxygen reduction reaction(ORR)electrocatalysts in metal-air batteries.However,the active sites in defective carbon are easily subjected to serious oxidation or hydroxylation during ORR or storage,leading to rapid degradation of activity.Herein,we design a van der Waals heterostructure comprised of vitamin C(VC)and defective carbon(DC)to not only boost the activity but also enhance the durability and storage stability of the DC-VC electrocatalyst.The formation of VC van der Waals between DC and VC is demonstrated to be an effective strategy to protect the defect active sites from oxidation and hydroxylation degradation,thus significantly enhancing the electrochemical durability and storage anti-aging performance.Moreover,the DC-VC van der Waals can reduce the reaction energy barrier to facilitate the ORR.These findings are also confirmed by operando Fourier transform infrared spectroscopy and density functional theory calculations.It is necessary to mention that the preparation of this DC-VC electrocatalyst can be scaled up,and the ORR performance of the largely produced electrocatalyst is demonstrated to be very consistent.Furthermore,the DC-VC-based aluminum-air batteries display very competitive power density with good performance maintenance.

Atomically dispersed Fe sites on hierarchically porous carbon nanoplates for oxygen reduction reaction

Developing cost-effective,robust and stable non-precious metal catalysts for oxygen reduction reaction(ORR) is of paramount importance for electrochemical energy conversion devices such as fuel cells and metal-air batteries.Although Fe-N-C single atom catalysts(SACs) have been hailed as the most promising candidate due to the optimal binding strength of ORR intermediates on the Fe-N_(4) sites,they suffer from serious mass transport limitations as microporous templates/substrates,i.e.,zeolitic imidazolate frameworks(ZIFs),are usually employed to host the active sites.Motivated by this challenge,we herein develop a hydrogen-bonded organic framework(HOF)-assisted pyrolysis strategy to construct hierarchical micro/mesoporous carbon nanoplates for the deposition of atomically dispersed Fe-N_(4) sites.Such a design is accomplished by employing HOF nanoplates assembled from 2-aminoterephthalic acid(NH_(2)-BDC) and p-phenylenediamine(PDA) as both soft templates and C,N precursors.Benefitting from the structural merits inherited from HOF templates,the optimized catalyst(denoted as Fe-N-C SAC-950) displays outstanding ORR activity with a high half-wave potential of 0.895 V(vs.reversible hydrogen electrode(RHE)) and a small overpotential of 356 mV at 10 mA cm^(-2) for the oxygen evolution reaction(OER).More excitingly,its application potential is further verified by delivering superb rechargeability and cycling stability with a nearly unfading charge-discharge gap of 0.72 V after 160 h.Molecular dynamics(MD) simulations reveal that micro/mesoporous structure is conducive to the rapid mass transfer of O_(2),thus enhancing the ORR performance.In situ Raman results further indicate that the conversion of O_(2) to~*O_(2)-the rate-determining step(RDS) for Fe-N-C SAC-950.This work will provide a versatile strategy to construct single atom catalysts with desirable catalytic properties.

Sulfur doped iron-nitrogen-hard carbon nanosheets as efficient and robust noble metal-free catalysts for oxygen reduction reaction in PEMFC

Transition metal-nitrogen-carbon(M-N-C)as a promising substitute for the conventional noble metalbased catalyst still suffers from low activity and durability for oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs).To tackle the issue,herein,a new type of sulfur-doped ironnitrogen-hard carbon(S-Fe-N-HC)nanosheets with high activity and durability in acid media were developed by using a newly synthesized precursor of amide-based polymer with Fe ions based on copolymerizing two monomers of 2,5-thiophene dicarboxylic acid(TDA)as S source and 1,8-diaminonaphthalene(DAN)as N source via an amination reaction.The as-synthesized S-Fe-N-HC features highly dispersed atomic Fe Nxmoieties embedded into rich thiophene-S doped hard carbon nanosheets filled with highly twisted graphite-like microcrystals,which is distinguished from the majority of M-N-C with soft or graphitic carbon structures.These unique characteristics endow S-Fe-N-HC with high ORR activity and outstanding durability in 0.5 M H_(2)SO_(4).Its initial half-wave potential is 0.80 V and the corresponding loss is only 21 m V after 30,000 cycles.Meanwhile,its practical PEMFC performance is a maximum power output of 628.0 mW cm^(-2)and a slight power density loss is 83.0 m W cm^(-2)after 200-cycle practical operation.Additionally,theoretical calculation shows that the activity of Fe Nxmoieties on ORR can be further enhanced by sulfur doping at meta-site near FeN_(4)C.These results evidently demonstrate that the dual effect of hard carbon substrate and S doping derived from the precursor platform of amid-polymers can effectively enhance the activity and durability of Fe-N-C catalysts,providing a new guidance for developing advanced M-N-C catalysts for ORR.

A Review of In‑Situ Techniques for Probing Active Sites and Mechanisms of Electrocatalytic Oxygen Reduction Reactions

Electrocatalytic oxygen reduction reaction(ORR)is one of the most important reactions in electrochemical energy technologies such as fuel cells and metal–O2/air batteries,etc.However,the essential catalysts to overcome its slow reaction kinetic always undergo a complex dynamic evolution in the actual catalytic process,and the concomitant intermediates and catalytic products also occur continuous conversion and reconstruction.This makes them difficult to be accurately captured,making the identification of ORR active sites and the elucidation of ORR mechanisms difficult.Thus,it is necessary to use extensive in-situ characterization techniques to proceed the real-time monitoring of the catalyst structure and the evolution state of intermediates and products during ORR.This work reviews the major advances in the use of various in-situ techniques to characterize the catalytic processes of various catalysts.Specifically,the catalyst structure evolutions revealed directly by in-situ techniques are systematically summarized,such as phase,valence,electronic transfer,coordination,and spin states varies.In-situ revelation of intermediate adsorption/desorption behavior,and the real-time monitoring of the product nucleation,growth,and reconstruction evolution are equally emphasized in the discussion.Other interference factors,as well as in-situ signal assignment with the aid of theoretical calculations,are also covered.Finally,some major challenges and prospects of in-situ techniques for future catalysts research in the ORR process are proposed.

Beads-on-string hierarchical structured electrocatalysts for efficient oxygen reduction reaction

Rational design of hierarchically structured electrocatalysts is particularly important for electrocatalytic oxygen reduction reaction(ORR).Here,ZIF-67 crystals are stringed on core-shell Ag@C nanocables using a coordinationmodulated process.Upon pyrolysis,Ag@C strings of Co nanoparticles embedded with three-dimensional porous carbon with beads-on-string hierarchical structures are developed.Due to the advantages of the rich electrochemical active sites of Co-based“beads”and the efficient electron transfer pathways via Ag@C“strings,”the resultant NH_(3)-Ag@C@Co-N-C-700 catalyst shows an improved electrocatalytic activity toward ORR.NH_(3)-Ag@C@Co-N-C-700 shows a high onset potential of 0.99 V versus RHE,a high half-wave potential of 0.88 V versus RHE,and a large limiting current of 5.8 mA cm^(-2),which are better than those of commercial Pt/C electrocatalysts.Additionally,the NH_(3)-Ag@C@Co-N-C-700 catalyst shows high stability and preeminent methanol tolerance,which makes NH_(3)-Ag@C@Co-N-C-700 a promising catalyst for oxygen electrocatalysis in fuel cell applications.

Upcycling end of lithium cobalt oxide batteries to electrocatalyst for oxygen reduction reaction in direct methanol fuel cell via sustainable approach

Recycling spent lithium-ion batteries(SLIBs)has become essential to preserve the environment and reclaim vital resources for sustainable development.The typical SLIBs recycling concentrated on separating valuable components had limitations,including high energy consumption and complicated separation processes.This work suggests a safe hydrometallurgical process to recover usable metallic cobalt from depleted LiCoO_(2)batteries by utilizing citric acid as leachant and hydrogen peroxide as an oxidizing agent,with ethanol as a selective precipitating agent.The anode graphite was also recovered and converted to graphene oxide(GO).The above components were directly resynthesized to cobaltintegrated nitrogen-doped graphene(Co@NG).The Co@NG showed a decent activity towards oxygen reduction reaction(ORR)with a half-wave potential of 0.880 V vs.RHE,almost similar to Pt/C(0.888 V vs.RHE)and with an onset potential of 0.92 V vs.RHE.The metal-nitrogen-carbon(Co-N-C)having the highest nitrogen content has decreased the barrier for ORR since the reaction was enhanced for Co@NG-800,as confirmed by density functional theory(DFT)simulations.The Co@NG cathode catalyst coupled with commercial Pt-Ru/C as anode catalyst exhibits excellent performance for direct methanol fuel cell(DMFC)with a peak power density of 34.7 mW cm^(-2)at a discharge current density of120 m A cm^(-2)and decent stability,indicating the promising utilization of spent battery materials in DMFC applications.Besides,lithium was recovered from supernatant as lithium carbonate by coprecipitation process.This work avoids sophisticated elemental separation by utilizing SLIBs for other renewable energy applications,lowering the environmental concerns associated with recycling.

Recent advances in regulating the performance of acid oxygen reduction reaction on carbon-supported non-precious metal single atom catalysts

Developing high performance and low-cost catalysts for oxygen reduction reaction(ORR)in challenging acid condition is vital for proton-exchange-membrane fuel cells(PEMFCs).Carbon-supported nonprecious metal single atom catalysts(SACs)have been identified as potential catalysts in the field.Great advance has been obtained in constructing diverse active sites of SACs for improving the performance and understanding the fundamental principles of regulating acid ORR performance.However,the ORR performance of SACs is still unsatisfactory.Importantly,microenvironment adjustment of SACs offers chance to promote the performance of acid ORR.In this review,acid ORR mechanism,attenuation mechanism and performance improvement strategies of SACs are presented.The strategies for promoting ORR activity of SACs include the adjustment of center metal and its microenvironment.The relationship of ORR performance and structure is discussed with the help of advanced experimental investigations and theoretical calculations,which will offer helpful direction for designing advanced SACs for ORR.

Co-Ru alloy nanoparticles decorated onto two-dimensional nitrogen doped carbon nanosheets towards hydrogen/oxygen evolution reaction and oxygen reduction reaction

Constructing highly-efficient electrocatalysts toward hydrogen evolution reaction(HER)/oxygen evolution reaction(OER)/oxygen reduction reaction(ORR)with excellent stability is quite important for the development of renewable energy-related applications.Herein,Co-Ru based compounds supported on nitrogen doped two-dimensional(2D)carbon nanosheets(NCN)are developed via one step pyrolysis procedure(Co-Ru/NCN)for HER/ORR and following low-temperature oxidation process(Co-Ru@RuO_(x)/NCN)for OER.The specific 2D morphology guarantees abundant active sites exposure.Furthermore,the synergistic effects arising from the interaction between Co and Ru are crucial in enhancing the catalytic performance.Thus,the resulting Co-Ru/NCN shows remarkable electrocatalytic performance for HER(70 mV at 10 mA cm^(-2))in 1 M KOH and ORR(half-wave potential E_(1/2)=0.81 V)in 0.1 M KOH.Especially,the Co-Ru@RuO_(x)/NCN obtained by oxidation exhibits splendid OER performance in both acid(230 mV at 10 mA cm^(-2))and alkaline media(270 mV at 10 mA cm^(-2))coupled with excellent stability.Consequently,the fabricated two-electrode water-splitting device exhibits excellent performance in both acidic and alkaline environments.This research provides a promising avenue for the advancement of multifunctional nanomaterials.

Identification of Dynamic Active Sites Among Cu Species Derived from MOFs@CuPc for Electrocatalytic Nitrate Reduction Reaction to Ammonia

Direct electrochemical nitrate reduction reaction(NITRR)is a promising strategy to alleviate the unbalanced nitrogen cycle while achieving the electrosynthesis of ammonia.However,the restructuration of the high-activity Cu-based electrocatalysts in the NITRR process has hindered the identification of dynamical active sites and in-depth investigation of the catalytic mechanism.Herein,Cu species(single-atom,clusters,and nanoparticles)with tunable loading supported on N-doped TiO_(2)/C are successfully manufactured with MOFs@CuPc precursors via the pre-anchor and post-pyrolysis strategy.Restructuration behavior among Cu species is co-dependent on the Cu loading and reaction potential,as evidenced by the advanced operando X-ray absorption spectroscopy,and there exists an incompletely reversible transformation of the restructured structure to the initial state.Notably,restructured CuN_(4)&Cu_(4) deliver the high NH_(3) yield of 88.2 mmol h^(−1)g_(cata)^(−1) and FE(~94.3%)at−0.75 V,resulting from the optimal adsorption of NO_(3)^(−) as well as the rapid conversion of^(*)NH_(2)OH to^(*)NH_(2) intermediates originated from the modulation of charge distribution and d-band center for Cu site.This work not only uncovers CuN_(4)&Cu_(4) have the promising NITRR but also identifies the dynamic Cu species active sites that play a critical role in the efficient electrocatalytic reduction in nitrate to ammonia.

Activation of Transition Metal(Fe,Co and Ni)-Oxide Nanoclusters by Nitrogen Defects in Carbon Nanotube for Selective CO_(2) Reduction Reaction

The electrochemical carbon dioxide reduction reaction(CO_(2)RR),which can produce value-added chemical feedstocks,is a proton-coupled-electron process with sluggish kinetics.Thus,highly efficient,cheap catalysts are urgently required.Transition metal oxides such as CoO_(x),FeO_(x),and NiO_(x)are low-cost,low toxicity,and abundant materials for a wide range of electrochemical reactions,but are almost inert for CO_(2)RR.Here,we report for the first time that nitrogen doped carbon nanotubes(N-CNT)have a surprising activation effect on the activity and selectivity of transition metal-oxide(MO_(x)where M=Fe,Ni,and Co)nanoclusters for CO_(2)RR.MO_(x)supported on N-CNT,MO_(x)/N-CNT,achieves a CO yield of 2.6–2.8 mmol cm−2 min−1 at an overpotential of−0.55 V,which is two orders of magnitude higher than MO_(x)supported on acid treated CNTs(MO_(x)/O-CNT)and four times higher than pristine N-CNT.The faraday efficiency for electrochemical CO_(2)-to-CO conversion is as high as 90.3%at overpotential of 0.44 V.Both in-situ XAS measurements and DFT calculations disclose that MO_(x)nanoclusters can be hydrated in CO_(2)saturated KHCO_(3),and the N defects of N-CNT effectively stabilize these metal hydroxyl species under carbon dioxide reduction reaction conditions,which can split the water molecules and provide local protons to inhibit the poisoning of active sites under carbon dioxide reduction reaction conditions.

PtCo-based nanocatalyst for oxygen reduction reaction:Recent highlights on synthesis strategy and catalytic mechanism

Oxygen reduction reaction over Pt-based catalyst is one of the most significant cathode reactions in fuel cells.However,low reserves and high price of Pt have motivated researchers worldwide seeking enhanced utilization efficiency and durability by doping non-noble metals to form Pt-based alloy catalysts.Alloying Pt with Co has been recognized as one of the most effective approaches to achieve this goal.PtCo bimetal combination is one of the most promising candidates to synthesize highly efficient catalysts for oxygen reduction reaction(ORR)applications,owing to its relatively more suitable oxygen binding energy for four-electron transfer reactions.Recently,impressive strategies have been developed to fabricate more active and stable PtCo-based multimetallic alloys with tailorable size and morphology.This paper aims to summarize the most recent highlights on the study of the relationship between preparation strategies,morphologies,electroactivities of the PtCo-based catalyst at atomic level and further the relevant reaction mechanism.The challenges and opportunities on the further development of electrocatalysts for fuel cells are included to provide reference for the practical application.

Rapid and durable oxygen reduction reaction enabled by a perovskite oxide with self-cleaning surface

The growth of electrochemically inert segregation layers on the surface of solid oxide fuel cell cathodes has become a bottleneck restricting the development of perovskite-structured oxygen reduction catalysts.Here,we report a new discovery in which enriched Ba and Fe ions on the near-surface of Nd_(1/2)Ba_(1/2)Co_(1/3)Fe_(1/3)Mn_(1/3)O_(3-δ)spontaneously agglomerate into dispersed Ba_(5)Fe_(2)O_(8) nanoparticles and maintain a highly active and durable perovskite structure on the surface.This unique surface selfcleaning phenomenon is related to the low average potential energy of Ba_(5)Fe_(2)O_(8),which is grown on the near-surface layer.The electrochemically inert Ba_(5)Fe_(2)O_(8) segregation layer on the near-surface of the perovskite catalyst achieves self-cleaning by regulating the formation energy of enriched metal oxides.This self-cleaned perovskite surface exhibits an ultrafast oxygen exchange rate,high catalytic activity for the oxygen reduction reaction,and good adaptability to the actual working conditions of solid oxide fuel cell stacks.This study paves a new way for overcoming the stubborn problem of perovskite catalyst surface deactivation and enriches the scientific knowledge of surface catalysis.

Microbial synthesis of N, P co-doped carbon supported PtCu catalysts for oxygen reduction reaction

Developing highly efficient and stable platinum-based electrocatalyst for oxygen reduction reaction(ORR) is critical to expediting commercialization of fuel cells.Herein,several PtCu alloy nanocatalysts supported on N,P co-doped carbon(PtCu/NPC) were prepared by microbial-sorption and carbonization-reduction.Among them,PtCu/NPC-700 ℃ exhibits excellent catalytic performance for ORR with a mass activity of 0.895 A mg_(pt)^(-1)(@0.9 V) which is 8.29 folds of commercial Pt/C.Additionally,the ECSA and MA of PtCu/NPC-700℃ only decrease by 14.2% and 18.7% respectively,while Pt/C decreases by 35.2% and 52.8% after 10,000 cycles of ADT test.Moreover,the PtCu/NPC-700℃ catalyst emanates a maximum power density of 715 mW cm^(-2) and only 11.1% loss of maximum power density after 10,000 ADTs in single-cell test,indicating PtCu/NPC-700℃ also manifests higher activity and durability in actual single-cell operation than Pt/C.This research provides an easy and novel strategy for developing highly active and durable Pt-based alloy catalyst.

Tuning the charge distribution and crystal field of iron single atoms via iron oxide integration for enhanced oxygen reduction reaction in zinc-air batteries

Metal-air batteries face a great challenge in developing efficient and durable low-cost oxygen reduction reaction(ORR)electrocatalysts.Single-atom iron catalysts embedded into nitrogen doped carbon(Fe-N-C)have emerged as attractive materials for potential replacement of Pt in ORR,but their catalytic performance was limited by the symmetrical electronic structure distribution around the single-atom Fe site.Here,we report our findings in significantly enhancing the ORR performance of Fe-N-C by moderate Fe_(2)O_(3) integration via the strong electronic interaction.Remarkably,the optimized catalyst(M-Fe_(2)O_(3)/Fe_(SA)@NC)exhibits excellent activity,durability and good tolerance to methanol,outperforming the benchmark Pt/C catalyst.When M-Fe_(2)O_(3)/Fe_(SA)@NC catalyst was used in a practical zinc-air battery assembly,peak power density of 155 mW cm^(-2)and specific capacity of 762 mA h g_(Zn)^(-1)were achieved and the battery assembly has shown superior cycling stability over a period of 200 h.More importantly,theoretical studies suggest that the introduction of Fe_(2)O_(3) can evoke the crystal field alteration and electron redistribution on single Fe atoms,which can break the symmetric charge distribution of Fe-N_(4) and thereby optimize the corresponding adsorption energy of intermediates to promote the O_(2)reduction.This study provides a new pathway to promote the catalytic performance of single-atom catalysts.

Exploring the contribution of oxygen reduction reaction to Mg corrosion by modeling assisted local analysis

Oxygen reduction reaction(ORR)has been disclosed in recent studies as a significant secondary cathodic process during magnesium corrosion.This work elaborates on the contribution of ORR to the total corrosion process of pure Mg at different impurity levels in NaCl electrolyte with the assistance of local techniques.A finite element based numerical model taking into account the contribution of ORR during the corrosion of the Mg test materials has been designed in this study considering the local oxygen concentration.Respective computational simulations were calibrated based on the experimental data and evaluated accordingly.Finally,the simultaneous monitoring of local concentration of H_(2) and O_(2),and the combined modeling study reveal the relation between ORR and hydrogen evolution reaction.

Bimetallic catalysts as electrocatalytic cathode materials for the oxygen reduction reaction in microbial fuel cell:A review

Microbial fuel cell(MFC) is one synchronous power generation device for wastewater treatment that takes into account environmental and energy issues, exhibiting promising potential. Sluggish oxygen reduction reaction(ORR) kinetics on the cathode remains by far the most critical bottleneck hindering the practical application of MFC. An ideal cathode catalyst should possess excellent ORR activity, stability, and costeffectiveness, experiments have demonstrated that bimetallic catalysts are one of the most promising ORR catalysts currently. Based on this, this review mainly analyzes the reaction mechanism(ORR mechanisms, synergistic effects), advantages(combined with characterization technologies), and typical synthesis methods of bimetallic catalysts, focusing on the application effects of early Pt-M(M = Fe, Co, and Ni) alloys to bifunctional catalysts in MFC, pointing out that the main existing challenges remain economic analysis, long-term durability and large-scale application, and looking forward to this. At last, the research trend of bimetallic catalysts suitable for MFC is evaluated, and it is considered that the development and research of metal-organic framework(MOF)-based bimetallic catalysts are still worth focusing on in the future, intending to provide a reference for MFC to achieve energy-efficient wastewater treatment.

Efficient hydrogen peroxide production enabled by exploring layered metal telluride as two electron oxygen reduction reaction electrocatalyst

It is of great interest to develop the novel transition metal-based electrocatalysts with high selectivity and activity for two electron oxygen reduction reaction(2e^(-) ORR).Herein,the nickel ditelluride(NiTe_(2)) with layered structure was explored as the 2e^(-) ORR electrocatalyst,which not only showed the highest 2e^(-) selectivity more than 97%,but also delivered a slight activity decay after 5000 cycles in alkaline media.Moreover,when NiTe_(2) was assembled as the electrocatalyst in H-type electrolyzer,the on-site yield of H_(2)O_(2) could reach up to 672 mmol h^(-1)g^(-1) under 0.45 V vs.RHE.Further in situ Raman spectra,theoretical calculation and post microstructural analysis synergistically unveiled that such a good 2e^(-) ORR performance could be credited to the intrinsic layered crystal structure,the high compositional stability,as well as the electron modulation on the active site Ni atoms by neighboring Te atoms,leading to the exposure of active sites as well as the optimized adsorption free energy of Ni to –OOH.More inspiringly,such telluride electrocatalyst has also been demonstrated to exhibit high activity and selectivity towards 2e^(-) ORR in neutral media.

Metal-organic framework-based materials as key components in electrocatalytic oxidation and reduction reactions

Studies have extensively addressed the development of electrocatalytic technologies for energy storage and conversion,fuel production,and environmental protection.Electrode processes such as different oxidation and reduction reactions play a vital and significant role in these technologies.In this regard,efficient,inexpensive,and stable electrocatalysts capable can significantly promote electrochemical reactions.Unique features of metal–organic frameworks(MOFs)such as their high porosity,tunable structure,size,and pore shape,high surface area,and redox properties have introduced them as an ideal electrocatalyst candidate.This review is thus aimed at elucidating the role of MOF-based materials(pristine,derivatives and composites)as efficient electrocatalysts in energy and sensing-related oxidation and reduction reactions such as oxygen reduction reaction(ORR),hydrogen oxidation reaction(HOR),carbon dioxide reduction reaction(CO_(2)RR),urea oxidation reaction(UOR),alcohol oxidation reaction(AOR),nitrogen reduction reaction(NRR),and glucose oxidation reaction(GOR)in advanced energy and sensing devices.Also,the structure–property relationship of the electrocatalyst was elaborated for each electrocatalytic reaction.Finally,perspectives on the potential research topics for practical use of MOF-based electrocatalysts are addressed.The present review can improve the interest in MOF-based electrocatalysts to study different oxidation and reduction reactions in energy and sensing systems.