Microscopic Regulation And Electrochemical Reaction Of Fe-based Single-atom Catalysts

Currently,with the depletion of non-renewable energy,people pay more and more attention to the development of sustainable energy.However,the adequate availability of sustainable energy is highly dependent on many fundamental catalytic processes.The single-atom catalysts（SACs）with high active sites and high selectivity can be used as efficient catalysts to catalyze reaction.Such as oxygen reduction reactions（ORR）,oxygen evolution reactions（OER）and carbon dioxide reduction reactions（CO₂RR）.However,not all single-atom catalysts have been found to have excellent activity in practical catalyst applications.Therefore,in this paper,regulation strategies of promoting the intrinsic electrocatalytic activity of SACs are summarized by modulating the environmental atoms and the guest groups.Firstly,the axially chlorine-coordinated monatomic iron material（FeN₄Cl-SAzyme）was synthesized by high-temperature pyrolysis methods.The half-wave potential(E_1/2)of FeN₄Cl-SAzyme was 0.885 V,which far exceeded that of the commercial Pt/C and other catalysts.Furthermore,FeN₄Cl-SAzyme exhibited excellent resistance to methanol as well as.The density functional theory（DFT）computations simulations showed that the Cl coordination effectively modulates the charge of Fe in FeN₄Cl-SAzyme,weakening its adsorption strength with OH*and thus achieving the better catalytic performance in alkaline conditions.Simultaneously,XPS analysis was performed on all synthesized samples to understand the bonding changes of the reactants before and after the oxygen reduction reaction.It was found that the Cl-ligated Fe-N₄catalyst has a high Fe-OOH ratio,which indirectly agreement with DFT calculations.Secondly,boron（B）doped FeN₄/C catalyst was synthesized by high temperature pyrolysis.The theoretical results revealed that B modulation effectively tunes the d-band center of the iron（Fe）active site to optimize its adsorption strength with oxygenated species,greatly enhancing oxygen reduction reaction（ORR）and oxygen evolution reactions（OER）activity.The above theoretical predictions was confirmed by experimental measurements:B-doped FeN₄/C（Fe-N₄-B）material was performed as the bifunctional catalyst for ORR and OER in alkaline with an overpotential of 0.371 V and 0.387 V,outperforming the commercial Pt/C and Ru O₂.Thirdly,the FeCl-NC was synthesized by high-temperature pyrolysis,and this catalyst has excellent catalytic activity for carbon dioxide reduction reactions.The Faraday efficiency（FE）for carbon monoxide（CO）production at-0.5 V vs.RHE potential was increased by 14.2%for the catalyst with the introduction of the guest group compared to without the guest group.