Preparation And Electrocatalytic Water Decomposition Performance Of Self-supported Transition Metal-based Electrode

Hydrogen energy has attracted much attention due to its high quality energy density and zero carbon emission.Water electrolysis is an ideal hydrogen production technology,but the actual operating voltage of the electrolyzer is much higher than the theoretical limit voltage due to the high activation barrier and sluggish kinetics of hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）.Suitable catalyst can effectively reduce the reaction overpotential and energy consumption of hydrogen production.At present,the high cost and scarce resources of commercial noble metal catalysts seriously hinder the large-scale application of hydrogen production from water electrolysis.Transition metal-based catalysts are the research focus in the field of electrocatalytic water decomposition,but their HER/OER bifunctional catalytic performance still needs to be improved.Therefore,this thesis takes transition metal materials as the research object.The self-supported transition metal-based electrode materials were developed and their electrocatalytic performance of water decomposition was studied by using self-supported substrate,adjusting the composition of catalyst and optimizing the microstructure.The main research contents and conclusions of this thesis are as follows:（1）Spheroid Ni-Fe bimetallic oxide and nano-flake Ni-Co bimetallic phosphide were successively grown on 3D porous foam nickel（NF）by two-step galvanostatic deposition,thus constructing a unique 3D/2D composite structure.The effects of deposition current and time on the microstructure and electrocatalytic water decomposition performance of the material were investigated.Under the optimized conditions,Ni Fe O_x/Ni Co P_x obtained a HER overpotential of 101 m V and an OER overpotential of 214 m V at the current density of 10 m A cm^-2.The alkaline electrolytic cell assembled by Ni Fe O_x/Ni Co P_x as cathode and anode had a cell voltage of 1.55 V,lower than the commercial Pt/C||Ir O₂.The results showed that Ni Fe O_x/Ni Co P_x successfully retained the OER performance of Ni-Fe oxide and HER performance of Ni-Co phosphide,realizing the synergistic catalytic effect between the two components.（2）A carbon composite trimetal alloy/phosphide composite（Ni Fe Mo-x P-C）supported on nickel foam was prepared by hydrothermal-H₂/Ar reduction method.The effects of sodium hypophosphite addition on the phase,morphology and electrochemical properties of the materials were studied.The results showed that the appropriate phosphorus content was beneficial to the exposure of active sites,and could accelerate the reaction kinetics and charge transfer process.When the phosphorus content was 10.46 wt.%,the obtained Ni Fe Mo-0.4P-C had an overpotential of 87 m V and 196 m V of HER and OER,respectively,and an electrolytic water voltage of only 1.50 V at 10 m A cm^-2.In addition,as the voltage did not rise during the 50 h chronopotentiometry test,it had a good long-term stability.The results demonstrated that alloy/phosphide composite can be successfully prepared by this method,which is beneficial to realize the catalysis of different components at the same time and improve the compatibility between HER and OER active sites,thus obtaining electrode materials with good bifunctional electrocatalytic performance.