Synthesis And Catalytic Properties Of Nickel-Based Nanocomposites Catalysts For Hydrogen Evolution Reaction In Neutral Medium

Hydrogen is a key secondary energy carrier for the future,and electrolysis technology has the potential to convert intermittent,fluctuating,and random renewable energy sources（such as wind and solar energy）into hydrogen energy.Achieving the hydrogen evolution reaction（HER）through electrolysis of water in a neutral electrolyte can avoid the adverse effects of acid corrosion and high p H values on the durability of the electrolysis cell and electrocatalyst.However,the low proton concentration and slow HER kinetics in neutral electrolytes make it challenging to develop efficient and sustainable neutral HER electrocatalysts.Nickel-based composite materials have been extensively studied for electrolytic hydrogen evolution due to their low cost,high reserves,good ductility,strong corrosion resistance,conductivity,and thermal conductivity.However,there are issues with high hydrogen overpotential and slow reaction rates in neutral electrolytes,so it is necessary to adjust the reaction interface through reasonable strategies to improve the neutral catalytic kinetics of nickel-based composite materials.This thesis mainly focuses on the design and modification of nickel-based composite materials from two aspects:reaction active area and intrinsic activity,and explores their hydrogen evolution performance in neutral electrolytes in-depth.The main contents are as follows:（1）The self-supporting three-dimensional core-shell nano-rod structure Cu@Ni-Mo-P/CF composite electrode was prepared as a neutral hydrogen evolution electrocatalyst using foam copper as the substrate,copper nanowires as the core of the three-dimensional core-shell structure,and Ni-Mo-P as the shell using immersion,electroreduction,and electrodeposition methods.At current densities of 10 and 100 m A cm^-2,the required overpotentials were only 35 and 195 m V,respectively,and the corresponding Tafel slopes were 50 m V dec^-1,which was significantly better than that of a platinum-carbon electrode.The electrocatalyst could run continuously under constant current for 25 h without obvious decay,demonstrating good stability.In addition,it also showed excellent performance in alkaline electrolytes,requiring overpotentials of 27,136,and 199 m V at current densities of 10,100,and 300 m A cm^-2,respectively,which was better than many reported non-noble metal hydrogen evolution electrocatalysts.Characterization and testing revealed that the modification of Mo elements can effectively regulate the electronic coordination environment of Ni-P,promote electron transfer efficiency,and improve the intrinsic activity of the material.Furthermore,the regulation of the nano-rod structure can increase the electrochemical active surface area and expose more hydrogen evolution active sites,thus showing excellent performance in neutral electrolytic hydrogen evolution systems.The synthesis of the three-dimensional core-shell nano-rod structure Cu@Ni-Mo-P/CF composite electrode provides a new choice and idea for the development of efficient and economical electrocatalysts in neutral and alkaline electrolytes.（2）A Ni-Mo-S nanosheet array was grown in situ on a foam copper substrate using a simple electrodeposition method.In neutral electrolyte,the three-dimensional Ni-Mo-S nanosheet array electrode exhibited overpotentials of 93 and 220 m V at hydrogen evolution current densities of 10 and 50 m A cm^-2,respectively,with a Tafel slope of 121m V dec^-1,which is comparable to that of the commercial precious metal Pt/C electrode.The catalyst was able to operate under constant current for 160 h,with only a 46 m V increase in overpotential,far superior to the stability of Pt/C in neutral electrolyte.Characterization and testing revealed that the modification of the anion S can effectively control the morphology of the nanosheet array,improve the electronic coordination environment of the metal sites,and enhance the material’s hydrogen evolution performance in neutral solution by increasing both the electrochemical active surface area and intrinsic activity.The three-dimensional Ni-Mo-S nanosheet array composite electrode has broad application prospects and tremendous value in neutral electrolyte hydrogen evolution.