Design Of P-block Metal Doped FeNi Transition Metal Catalyst And Its Mechanism Of Electrochemical Water Splitting

Noble metal oxides（Ru O₂,Ir O₂）are recognized as the best OER catalysis,while which can not be applied in large-scale industrialization due to low reserves and high cost.Therefore,it is urgent to develop cheap and efficient catalysts for OER.Transition metal oxides（TMOs）in non-noble metal catalysts have been widely studied because of their excellent theoretical oxygen evolution performance and low cost.It is difficult to improve the catalytic activity of TMOs,while high-valence metal（such as W,Mo,Nb）doping is an important way to improve the performance of TMOs for OER performance through its covalency competition mechanism,in which enhance the activity by regulating cationic exposure of active site.Similarly,p-block metals have the same effect but have not received much attention from researchers.Hence our research rationally designed transition metal bimetal oxide catalyst and explored the reaction mechanism combed with DFT calculations.In our study,Fe Ni bimetallic oxide catalyst was synthesized by hydrothermal reaction and heat treatment.The successful synthesis of pure-phase Ni Fe₂O₄ material and doping of p-block metals was confirmed by XRD,SEM,TEM and XPS etc.The performance improvement effect of p-block metal doping in alkaline environment is as follows:Bi-NFO>Sb-NFO>NFO>Sn-NFO,in which Bi-NFO shows superior electrocatalytic performance towards the OER with a low overpotential of 250 m V at10 m A/cm~2 and a small Tafel slope of 43.3 m V/dec.Our study also explored the activity effected by Bi doping amount and verify the volcanic relationship between Bi doping amount and OER activity,in which 1/50Bi is the optimal with the highest OER activity.Our investigation also revealed the OER enhancement mechanism and reaction process through in situ characterization and DFT calculation.It is found that*OH has been adsorpted on the catalyst surface before oxygen evolution,p-block metal doping changes the local charge density of NFO,the d-band center shift positively after doping resulting enhancement of intermediates oxygen species adsorption thus improving the OER activity.Besides,the energy barrier of the four-electron reaction steps changes after doping.Particularly,the rate-determining step changes from the 2nd reaction step（*OH→*O）to the 3rd（*O→*OOH）after Bi doping.The calculated energy barrier of the rate-determining step reveals the theoretical activity which conforms with the experimental results.