Investigation On Preparation And Electrocatalytic Water Splitting Performances Of Transition Metal Sulfides

Electrocatalytic water splitting is an attractive energy conversion scheme that can overcome reliance on depleting fossil fuel reserves and prevent serious global climate degradation.Hydrogen energy,as a clean and efficient energy source,produces no pollution and carbon emissions during its conversion process,with water being the only byproduct.Countless researchers around the world are studying how to improve the performance of water splitting,specifically the electrocatalysts that affect the hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）and reduce the overpotential in the water splitting process.The theoretical voltage of water splitting in the electrocatalytic process is 1.23 V,but in practical experiments,the complex electron and ion transfer processes lead to slow kinetics,low efficiency,and large energy losses.Therefore,developing new efficient electrocatalysts to reduce overpotential and minimize losses in the water splitting process is critical.Precious metals have excellent electrocatalytic properties in the electrocatalytic field,but their high cost and limited reserves make them unsuitable for large-scale applications.Therefore,developing water splitting electrocatalysts that are rich in reserves,highly efficient,and low-cost has become a hot research topic.Transition metal sulfides,as a new type of electrolytic material,have emerged in the water splitting field due to their excellent catalytic activity,adjustable structure,renewability,and environmental friendliness.Moreover,the in-situ growth strategy of self-supported electrodes eliminates the need for additional conductive and adhesive agents,reducing overpotential and minimizing energy loss in the water splitting process.This article uses an in-situ growth strategy to directly generate sulfide nanoparticles on foam Ni/Ni Fe to enhance the efficiency of electrocatalytic water splitting.The desired product was prepared by the"anodic oxidation-sulfurization"method.The intermediate product Ni C₂O₄ was obtained by anodic oxidation,and the desired product Ni S was prepared by sulfurization.The surface nanostructure of the product was determined by SEM,which showed that one-dimensional nano-rod structures of Ni C₂O₄ grew directly on the surface of the foam Ni,and Ni S further increased the surface area and enhanced the catalytic performance by inheriting the one-dimensional nanostructure of Ni C₂O₄.XRD was used to confirm the generation of the desired product.TEM further confirmed its nanostructure,and the polycrystalline structure of the product was verified by HRTEM and SAED.XPS analysis showed the presence of Ni³⁺and Ni²⁺valence states in the sample.After determining the sample composition,electrochemical testing was carried out,and the Ni S/Ni electrode showed excellent electrocatalytic activity in a 1 mol L^-1 KOH alkaline solution compared with the intermediate product Ni C₂O₄/Ni and the substrate foam Ni electrode.The stability of the sample was then determined by stability testing.Ni Fe sulfides were prepared by a"soak-sulfuration"method.Firstly,the intermediate product Ni Fe C₂O₄ was prepared by soaking at 45℃in a water bath,and then Ni Fe S was prepared by sulfuration at different temperatures.XRD testing confirmed that the Fe element in the product was present in a solid solution form in the Ni lattice,which was confirmed again by SAED.SEM testing showed that the foam Ni Fe formed a mesh-like nanostructure on the surface after soaking,and the original mesh structure was transformed into a two-dimensional nano-sheet after sulfuration,which was further confirmed by TEM.The polycrystalline structure of the product was confirmed by HRTEM and SAED.XPS further confirmed the presence of Ni^δ+and Ni²⁺and Fe³⁺in the sample,which were formed from the foam Ni Fe substrate and the Ni Fe S surface oxidation state,respectively.Electrochemical testing of the sample showed that a current density of 10 m A cm^-2 could be achieved at an overpotential of230 m V.After 24 hours of electrochemical testing,the electrochemical performance of the sample changed slightly,indicating good stability of the material.