Preparation And Electrocatalytic Water Splitting Performance Of Nickel Foam-Based MoS₂ Composite Electrode

Hydrogen energy is considered an ideal substitute for fossil fuels due to its high energy density and environmental friendliness.Compared with the traditional hydrogen production process,water electrocatalysis for hydrogen production owns the advantages of environmental protection and high efficiency,so it has received extensive attention from researchers.Researchers have recently devoted themselves to developing multifunctional non-precious metal catalysts to replace noble metal materials represented by ruthenium oxide/iridium oxide（Ru O₂/Ir O₂）and platinum（Pt）.However,most non-precious metal catalytic systems suffer from poor electrical conductivity and mechanical stability,limiting their catalytic performance.Therefore,developing new non-precious metal materials with good mechanical stability and high electrical conductivity is a current research focus.Based on this,this research intends to synthesize molybdenum disulfide（MoS₂）-based three-dimensional self-supporting electrode materials with good mechanical stability and electrical conductivity by hydrothermal method and further improve the conductivity and catalytic performance of MoS₂ by compounding with graphene and rare-earth doping.Finally,a novel electrocatalytic material system with excellent performance has been obtained.The specific work content is as follows:（1）A self-supporting three-dimension catalytic system composed of MoS₂ nanoarrays attached to the NF substrate has been successfully fabricated by a one-step hydrothermal process.And various hydrothermal reaction parameters on the microstructure of the nanocrystals were systematically investigated.Results revealed that the catalyst with the initial Mo/S=1/2 delivered an overpotential of 160 m V(η₁₀)for hydrogen evolution reaction（HER）,and its corresponding Tafel slope was 133m V dec^-1.Besides,the catalyst also exhibited an overpotential of 254 m V(η₁₀)with the corresponding Tafel slope of 108.1 m V dec^-1 for oxygen evolution reaction（OER）.（2）A graphene-coated nickel foam material was prepared by chemical vapor deposition.Subsequently,MoS₂ with a nano-flower-like structure was deposited on the surface of graphene by a hydrothermal synthesis process.Graphene plays a protective role on the nickel foam skeleton,and the material exhibits good mechanical stability both in the alkaline and the acidic media.In an alkaline medium,the MoS₂/Gr/NF-24 h shows improved electrocatalysis performance,requiring an overpotential of 136 and 288 m V for HER and OER reactions,respectively.Moreover,in the acidic medium,the MoS₂/Gr/NF-24 h composite exhibited an overpotential of 91 m V at a current density of 10 m A cm^-2,and the corresponding Tafel slope was 97 m V dec^-1.（3）To further improve the electrochemical activity of MoS₂,MoS₂ was doped with rare earth elements,including cerium（Ce）,lanthanum（La）and neodymium（Nd）.Their potential effects on the crystal phase and microstructure of MoS₂ were systematically investigated.The results showed that the Ce doping significantly improved the electrocatalytic activity of the material.In the case of the HER,the Ce-MoS₂/Gr/NF exhibited an overpotential of 106 m V(η₁₀)and 74 m V(η₁₀)under acidic and alkaline mediums,respectively;and its corresponding Tafel slope was 85.9 m V dec^-1 and74.4 m V dec^-1,respectively.