Study On The Preparation Of Nickel/Copper-based Self-supported Non-noble Metal Composite Catalysts And Their Electrocatalytic Performance For Water Decomposition

With the continuous depletion of fossil fuels and the worsening of environmental climate,electrolytic water splitting for hydrogen production is considered an effective approach to overcome the energy crisis and reduce carbon dioxide emissions.During the process of electrolytic water splitting,the anode undergoes the oxygen evolution reaction（OER）,and the cathode undergoes the hydrogen evolution reaction（HER）.High-efficiency electrocatalysts play a crucial role in improving the slow reaction kinetics in electrolytic water splitting.Noble metal electrocatalysts are considered efficient HER and OER catalysts due to their low overpotential.However,their high cost and low natural abundance limit their widespread application.In contrast,non-noble metal materials have garnered extensive attention due to their abundant content,low cost,tunable composition,and excellent catalytic activity.Traditional non-noble metal electrocatalysts for electrode construction use a drop-casting process,which is complex,time-consuming,and not conducive to electron transfer between active sites.Constructing self-supported electrocatalysts in situ modification involves growing active materials directly on a conductive substrate.This not only reduces costs and simplifies operations but also forms unique nanostructures on the substrate surface,exposing active surface sites and promoting charge transfer,further improving catalytic performances.However,the intrinsic activity of single-component in situ modified catalysts is limited,and their stability during the gas generation process in water decomposition needs further improvement.In this study,through self-supporting in situ modification,a series of low-cost,efficient,and stable non-noble metal composite electrocatalysts were prepared using strategies such as heterojunction interfaces and heteroatom doping.The electrocatalytic performances and related mechanisms were discussed,providing important references for the promotion and application of non-precious metal composite materials in electrolytic hydrogen production.The main research results are as follows:1.A self-supported Carbon Quantum Dots（CQDs）loaded and Cu-Mo dual-doped CQDs-Cu-Mo-Ni₃S₂@NF composite material was in situ constructed on Nickel Foam（NF）through a simple hydrothermal method.This section explored in detail the effects of different Cu/Mo molar ratios,L-cysteine content,and reaction temperature on the synthesis of materials.Characterization techniques were used to study the phase structure,morphology,and other characteristics,and its electrocatalytic performance was evaluated through electrochemical tests.The results showed that CQDs-Cu-Mo-Ni₃S₂@NF,which had a highly porous ultra-thin nanosheet interwoven network structure,as a working electrode,exhibited a low overpotential of 131 m V for HER in an alkaline environment at the current density of 10 m A cm^-2.The current density hardly decreased before and after the stability test,demonstrating good stability with durability of at least 30 h.The study found that the synergistic effect between CQDs and Cu-Mo bimetallics was the main reason for its excellent electrocatalytic performance.In addition,the co-catalyst CQDs not only induced charge redistribution in hybrid materials but also protected the transition metal substrate from oxidation/hydroxylation,ensuring superior durability of the electrocatalyst.Its excellent conductivity further enhanced the overall catalytic activity of the catalyst.Density Functional Theory（DFT）analysis revealed that this synergy included optimized water molecule adsorption/desorption,weakening of the strong S-H bond interaction on Ni₃S₂ surface,and providing sufficient active centers.2.N,Fe-Ni₃S₂@NF composite material with abundant pores was prepared by in situ etching growth and one-step calcination on NF using different amounts of Fe（NO₃）₃·9H₂O,Thiourea（TAA）,and calcination temperature.N,Fe-Ni₃S₂@NF catalyst,as a working electrode for water electrolysis,exhibited a low overpotential of121 m V at the current density of 10 m A cm^-2 for HER,a Tafel slope of 41.2 m V dec^-1,and a long-term durability of nearly 140 h.DFT calculations showed that N,Fe co-doping strategy optimized Gibbs energy of hydrogen intermediates,enhancing the intrinsic activity of the catalyst.This“integrated”growth method in situ avoided the use of binders effectively,which enhanced the mechanical strength and conductivity of the catalyst.By introducing TAA with both sulfurization and nitrogenation functions,nitrogenation and sulfurization of transition metal active centers were achieved,forming a more stable N,Fe co-doped Ni₃S₂ in situ modification catalyst,effectively enhancing its activity and stability.3.Self-supported Ni₂Co₁ LDH-Ce O_x/Ni₃S₂@NF composite material was constructed by synthesizing Ce O_x-modified nickel-cobalt layered double hydroxide（Ni Co LDH）on NF through a simple hydrothermal method.Experimental results showed that Ni₂Co₁ LDH-Ce O_x/Ni₃S₂@NF material had a nano-sheet interwoven vertical array structure.In 1 mol L^-1 KOH medium,when the current density was 100m A cm^-2,the overpotentials for HER and OER were 250 m V and 300 m V,respectively,with Tafel slopes of 92 m V dec^-1 and 52 m V dec^-1,and durability of at least 45 h and50 h,respectively.The high porosity of Ni₃S₂@NF nano-network framework combined with oxygen-deficient Ce O_x nanoparticles modification of Ni Co LDH nano-sheets resulted in excellent electrochemical performance and stability of Ni₂Co₁ LDH-Ce O_x/Ni₃S₂@NF structure.The study found that the synergistic effect significantly redistributed the electron cloud,generated surface-induced potential,reduced the overpotential,and activation energy of the catalytic reaction.DFT calculations also showed that the introduction of Ce O_x reduced the Gibbs free energy,i.e.,the main energy barrier of HER and OER pathways on Ni₂Co₁ LDH-Ce O_x/Ni₃S₂@NF,and the construction of multi-component electrocatalysts synergistically promoted HER and OER processes.4.The self-supported composite（CW@Cu^ⅡO/Cu^ⅡS/Cu（OH）₂）was prepared by in situ etching directly on the copper wire（CW）using CW as a substrate and a source of Cu.Due to its structure with rough and porous surface morphology and fast charge transfer kinetics,this self-supported catalyst demonstrated the ability to generate hydrogen and oxygen at a lower potential,displaying an overpotential of 290 m V at 10m A cm^-2 for OER.For HER,it exhibited an overpotential of 267 m V at 50 m A cm^-2.Besides,the pore structure of the catalyst remained well before and after reaction,contributing to its stability.The rough surface structure with abundant heterogeneous interfaces promoted synergistic effects among the active components and improved its conductivity.Consequently,this electrocatalyst demonstrated excellent catalytic performance.