Preparation Of Iron-based Bimetallic Hydroxide And Their Compositions And The Electrocatalytic Properties On The Oxygen Evolution Reaction

Hydrogen as an energy source has many advantages,such as environmental friendliness,high efficiency,and rich application scenarios,and will become an important medium for the energy structure change of the industry.Water electrolysis for hydrogen production is expected to be one of the mainstream methods for hydrogen production.However,in actual production,the efficiency of water electrolysis is low,which is mainly limited by the oxygen evolution reaction on the anode,thus affecting the development of hydrogen production process by water electrolysis.Therefore,finding a suitable oxygen evolution catalyst is particularly important for the development of water electrolysis.Bimetallic hydroxides have attracted much attention in electrochemical field,especially in oxygen evolution reaction electrocatalysis.Herein,different bimetallic hydroxides were prepared on nickel foam（NF）substrate and the structure related electrocatalytic properties were studied.Compounding with other materials and doping with metal cations were applied to improve the oxygen evolution performance.It mainly includes the following three parts:1.Synthesis of NiTe and Ni Fe-OH composite catalysts for oxygen evolution reaction by two-step deposion method.NiTe nanorods were first prepared on NF to form NiTe/NF composite by hydrothermal method.Followed by growing another layer of Ni Fe-OH on the NiTe nanorods by electrodeposition to obtain the composite catalysts NiTe@Ni Fe-x/NF（x is the deposition time of Ni Fe-OH）.It is found that the three-dimensional core-shell structure of the catalysts formed by the combination of NiTe and Ni Fe-OH have large specific surface areas,which is beneficial to exposure and accessibility of the active sites.When the deposition time was 900 s,the catalyst NiTe@Ni Fe-900/NF had the best oxygen evolution performance with an overpotential of 251 m V to reach 50 m A/cm² and a Tafel slope of 59.67 m V/dec.2.Synthesis of CoFe-OH and CoNi-OH composite catalysts for oxygen evolution reaction by two-step electrodeposition method.CoFe-OH was first electrodeposited on NF with the deposition time of 500 s to form CoFe-500/NF catalyst with the optimized loading content of CoFe-OH.Subsequently,CoNi-OH was electrodeposited on CoFe-500/NF to obtain the composite catalyst CoFe-500@CoNi-y/NF（y is the deposition time of CoNi-OH）.It is found that the hierarchical structure formed by CoFe-OH and CoNi-OH imporves the electrochemical active area of the catalyst,which is beneficial to exposure of the active sites and improvement of the electrocatalytic properties.CoFe-500@CoNi-150/NF shows the best electrocatalytic performance with the overpotential of 221 m V to achieve 10 m A/cm²,and the Tafel slope of 34.56 m V/dec.The effect of the deposition sequence of CoFe-OH and CoNi-OH on the electrocatalytic performance for oxygen evolution reaction was investigated.3.Synthesis of Cu-doped CoFe-OH catalysts for oxygen evolution reaction by one-step electrodeposition method.The total amount of metal ions of Co,Fe and Cu in the electrolyte keeps constant,Co_1-xFe_1-xCu_2x/NF（x=0.01,0.02,0.03,0.04,0.05）with different Cu doping content were obtained.Among the studied catalysts,Co_0.96Fe_0.96Cu_0.08/NF exhibits the best electrocatalytic activity with the overpotential of226 m V to achieve 10 m A/cm²,and the Tafel slope of 34.03 m V/dec.It is suggested that Cu doping can adjust the electronic structure and improve the conductivity of the catalyst,therefore to improve the electrocatalytic activity of the catalysts.