Study On The Metal Synergy Mechanism Of High Entropy Nanocatalyst To Enhance The Electrocatalytic Oxygen Evolution Performanc

With the rapid increase of demand for green hydrogen,the development of electrolytic water technology has been widely concerned.Efficient oxygen evolution catalyst provides feasibility for hydrogen production by electrolysis of water.High entropy alloy（HEAs）catalysts have been widely studied in the field of electrocatalytic oxygen evolution in recent years due to their ordered structure and tunability.In this paper,a series of electrocatalytic oxygen evolution（OER）catalysts with high activity have been obtained by combining the structural advantages of high entropy materials.The research content of this paper is as follows:1.Electrochemical hydrolytic hydrogen production is the most promising method for renewable energy storage and conversion.However,the kinetic slow oxygen evolution reaction（OER）limits the development of water electrolysis at the anode.The state-of-the-art OER catalysts are faced a dilemma of the high content of noble metals and low OER activities.Herein,a strategy for achieving efficient and stable high entropy alloy（HEA）catalysts by Mo coordination is reported.The earth-abundant Fe Co Ni Mo HEA catalyst provides an overpotential as low as 250 m V at the current density of 10 m A cm^-2in alkaline medium,which is 89 m V lower than that of the state-of-the-art Ir O₂.The turnover frequency（TOF）of 0.051 s^-1 at the overpotential of 300 m V of Fe Co Ni Mo HEA is 3 times higher than that of commercial Ir O₂ catalyst,and even 11 times higher than that of the Fe Co Ni alloy without Mo-coordination.Importantly,the Fe Co Ni Mo HEA exhibits excellent OER stability at a high current density of 100 m A cm^–2.Methanol molecular probe experiment and XPS analyses suggest that the electrons of Mo transfer to Fe,Co and Ni in the Fe Co Ni Mo HEA catalyst,which leads to a weakened OH^*bonding,and as a result the enhanced OER performance of Fe Co Ni Mo HEA catalyst.Consistent with the methanol molecular probe analysis,the real-time OER kinetic simulation reveals that the coordination of Mo within Fe Co Ni can speed up the rate-determining OH*deprotonation step of OER.Our finding opens up a routine for designing efficient cost-effective electrocatalysts for OER,which could facilitate discoveries in OER catalysts.2.It is an urgent and challenging requirement to build highly stable oxygen evolution reaction（OER）electrocatalysts under harsh industrial conditions.Herein,we report the first successful fabrication of robust high-entropy alloy（HEA）and High-entropy oxide（HEO）heterostructures by spontaneous reconstructing from HEA for efficient OER electrocatalysis.Density functional theory（DFT）calculations have revealed that the formation of the HEA-HEO heterostructure has offered highly electroactive sites for OER,which not only improves the electroactivity but also achieves the robust valence states of active sites to guarantee the long-term stable OER process.Benefiting from this desired electronic structure,the FeCoNiMnCr HEA-HEO catalyst exhibits negligible activity loss after maintaining at 100 m A cm^–2 as long as 240 h,and equally important is its excellent activity with the low overpotential of 320 m V at 500 m A cm^–2.Remarkably,the FeCoNiMnCr HEA-HEO catalyst possesses outstanding long-term stability even under the harsh industrial condition（6 M KOH and 85℃）at the current density as high as 500 m A cm^-2 over 500 hours,representing one of the most stable OER catalysts.This work provides a new perspective for designing and constructing efficient high-entropy electrocatalysts for industrial water splitting.3.A High-entropy alloy structure control strategy induced by high-valence metal engineering strategy was developed to convert polymetallic alloy sites into dual-structure high-entropy alloy/oxides into polyphase electrocatalytic active sites.Methanol probe experiment showed that the high entropy heterogeneous catalyst FeCoNiMnCr HEA/HEO nanoparticles formed by Cr metal with low electronegativity and inert adsorption of OER intermediates would effectively optimize the adsorption energy of reactant intermediates through strong local electron interaction caused by electronegativity difference.The current difference generated by the combination of the catalyst surface with OH*is not strong or weak,thus promoting the precipitation of O₂.FeCoNiMnCr HEA/HEO showed excellent electrochemical stability for oxygen evolution reaction(255 m V at 10 m A cm^-2),superior to the reference Pt/C and Ir O₂ catalysts.FeCoNiMnCr HEA-HEO was prepared to achieve a high anode current density of 500 m A cm^-2 within 112 hours.This is much lower than the most advanced Ir O2.This work has led to a breakthrough in the design of advanced high entropy electrocatalysts for electrocatalysis of OER reactions.