Controlled Synthesis Of Nickel-based Nanocatalytic Materials And Their Surface Reconstruction And Electro-catalytic Performance

As a new type of renewable energy,hydrogen energy has the characteristics of zero carbon emission,high energy density,and high energy conversion efficiency.It is an important energy to achieve the goal of getting rid of fossil energy and promote the rapid development of low-carbon economy.Water electrolysis is an advanced hydrogen production technology,which has the advantages of simplicity,quickness,and green.It can effectively solve the hydrogen energy industry’s demand for purity and cheapness.Oxygen evolution reaction（OER）is a key step in the process of water electrolysis,but the reaction pathway is complex,the kinetics are slow,and the energy consumption is much higher than the theoretical value.Therefore,it is essential to synthesize a catalyst with excellent performance for accelerating the reaction process and improving the energy conversion efficiency.Focusing on industrial applications,the development of OER catalysts with high activity,low price,and suitable for large current density is the top priority of the development of water electrolysis technology.At the same time,it is also feasible to find a reaction with a lower theoretical potential to replace the oxygen evolution reaction.In recent years,the Chemicals-assisted hydrogen electrocatalytic evolution reaction using small molecular substances such as urea and hydrazine hy-drate as sacrificial agents has received extensive attention from researchers.The oxi-dation reaction can purify wastewater rich in urea and hydrazine hydrate,which has both economic and environmental benefits.However,Chemicals-assisted hydrogen electrocatalytic evolution reaction also suffers from slow kinetics and the cost of pre-cious metal catalysts.Therefore,the first priority is to develop efficient,low-cost,and non-noble metal catalysts.The outer orbital electronic structure of nickel is similar to that of noble metals,and its compounds,as a class of promising catalytic materials,can realize the equivalent replacement of noble metal catalysts.Based on the above research background,this paper takes nickel-based nanocata-lytic materials as the entry point,and synthesizes efficient and stable nickel-based cat-alysts through functional strategies,such as interface engineering,heteroatom doping,vacancy engineering and reconstruction engineering.The specific research contents are as follows:1.Using Nickel foam as the substrate,smooth nanosheets were in situ grown on its surface as the precursor,and then the precursor was phosphated in N₂ atmosphere by chemical vapor deposition（CVD）.Finally,Fe₂P/Co₂P/Ni₂P heterojunction is formed.By systematically studying the electronic structure,surface composition and morphology of the catalyst before and after OER reaction,the relevant factors affecting the catalytic activity were determined.The results show that the material exhibits ex-cellent OER catalytic activity due to the abundant heterointerface,porous structure,and oxyhydroxide active species formed by surface reconstruction.When the current density reaches 500 and 1000 m A·cm^-2 in 1.0 M KOH,the overpotential is 281 and318 m V,respectively.This work provides a unique idea for designing high-perfor-mance OER electrocatalysts suitable for large current density,which will help further promote large-scale applications of water electrolysis for hydrogen production.2.Through the functional optimization strategy of heteroatom doping,Fe doped Ni₃S₂ nanosheets were supported on nickel foam.Combined with various characteri-zations,it is proved that the doping of Fe atoms not only optimize the electronic struc-ture of Ni₃S₂,but also activates the lattice oxygen oxidation mechanism,thereby accel-erating the reaction kinetics and improving the catalytic activity.After the OER reac-tion,the surface of the catalyst undergoes surface reconstruction,and the Ni²⁺is con-verted into the active site Ni³⁺for the Urea oxidation reaction（UOR）.3.Mo Ni alloy nanoparticles supported on carbon cloth were synthesized by electrodeposition method,and then etched with acetic acid and treated with cyclic volt-ammetry（CV）.Mo and Ni vacancies were introduced into Mo Ni alloy.Combined with various characterizations,the effects of Mo vacancies and Ni vacancies on the catalytic activity were systematically investigated.The research results show that the etching effect of acetic acid causes part of Ni to be leached from the surface of the catalyst to form Ni vacancies,while during the CV treatment,Mo continues to be leached out,which causes the surface of the catalyst to reconstruct and create a large number of Mo vacancies.Mo vacancies and Ni vacancies not only synergistically optimize the elec-tronic structure of the catalyst,but also act as active sites to promote the reaction,and the catalytic activity of the material is greatly improved.The hydrazine oxidation as-sisted hydrogen generation（OHz S）system built with this material as a bifunctional catalyst has excellent low-potential hydrogen production characteristic.