Synthesis And Electrocatalytic Performance Of Transition Metal Sulfides/Mo₂N

Electrocatalytic water splitting has gradually become a research hotspot as a stable hydrogen production technology.This phenomenon includes anodic oxygen evolution reaction（OER）and cathodic hydrogen evolution reaction（HER）,but the high energy barrier and slow kinetic process during the reaction process hinder the large-scale application of electrocatalytic water splitting in hydrogen production technology,thus,it is of great significance to develop catalysts with efficient electrocatalytic water splitting catalytic activity.Transition metal-based sulfur compounds,as substitutes for rare and noble metal-based electrocatalysts,have received extensive attention because of abundant reserves,low cost and green environmental protection.However,poor electrical conductivity and few active sites hinder their application in the field of electrocatalytic water splitting.Therefore,in this thesis,the HER and OER properties of transition metal sulfides are improved by constructing composite materials to achieve interfacial regulation.Firstly,Mo₂N/Co S₂ composites are formed by uniformly loading Co S₂ particles on the surface of porous Mo₂N by the hydrothermal method.The construction of a highly conductive interface in the composite material promotes the kinetics and thermodynamics of the HER reaction and reduces the overpotential of the reaction.Mo₂N/Co S₂exhibits excellent HER electrocatalytic performance in acidic and basic solutions,and its performance is better than most of the reported transition metal sulfide electrocatalysts.At high current densities(>100m A cm^-2),the required overpotential is lower than that of commercial Pt/C electrocatalysts.The theoretical calculation results show that the charge at the interface of the composite is redistributed,reducing the hydrogen absorption adsorption energy required for the HER reaction,and the adsorption energy required by different active sites increases with the increase of the distance from the interface.In the photovoltaic-driven water splitting experiment,HER catalyst Mo₂N/Co S₂ converts solar energy into hydrogen energy with a Faradaic efficiency of 97.8%and an energy conversion efficiency of 5.1%,indicating the bright application of Mo₂N/Co S₂ composite in the field of photoelectric catalytic water splitting prospect.In addition,Mo₂N/Ni S electrocatalytic water splitting catalyst was prepared by the same method,and Mo₂N/Ni S exhibited excellent electrocatalytic HER and OER performance in alkaline solution.When the current density is 10 m A cm^-2,the required overpotentials of Mo₂N/Ni S-5:1 material are 254 m V（HER）and 298 m V（OER）,respectively,which are much lower than that of single-component Mo₂N and Ni S.Moreover,Mo₂N/Ni S-5:1 exhibits excellent long-term stability in the two-electrode water electrolysis experiment.A total water splitting catalyst Mo₂N/Ni S material converts solar energy into hydrogen energy with a Faradaic efficiency of 96.3%and an energy conversion efficiency of 8.4%.The highly conductive interface significantly reduces the electrochemical impedance during the catalytic process and increases the electrochemical active area of the material.The synergistic effect of multiple factors enables the material to have both good HER and OER activities.