Construction Of Self-supporting NiCu-based Sulfide Electrode And Its Catalytic Performance Toward Electrochemical Water Splitting

With the rapidly development of industrial civilization,humans have become increasingly dependent on traditional energy sources.Meanwhile,environmental problems such as the global energy crisis and the greenhouse effect caused by the excessive use of fossil energy have become urgent problems that humans need to solve.Constructing a future new energy system and developing conversion and storage technologies for green and sustainable energy have become hot issues in countries around the world.As a clean energy carrier with the most potential for sustainable development,hydrogen energy has the advantages of no pollution,high combustion calorific value,and various preparation methods.The electrolysis water hydrogen production technology has the characteristics of high hydrogen production purity and no pollution in the preparation process.It is considered to be an environmentally friendly hydrogen production technology with great potential for large-scale application.The process of electrolyzed water is divided into two half reactions of cathodic hydrogen evolution reaction（HER）and anodic oxygen evolution reaction（OER）.However,the problems of high overpotential and high energy consumption in the reaction process seriously limit its application in industry.Thus,it is of great practical significance to find a cheap,efficient and stable catalyst to overcome the energy barrier during the reaction.Based on metal micro-alloying and rapid solidification,a self-supporting three-dimensional multi-level porous catalytic electrode is further prepared by chemical or electrochemical dealloying methods.The strategy for constructing active sites on it is expected to play a crucial role in the field of water electrolysis.Therefore,this article will focus on the construction of porous metal sulfide and its application in catalytic electrolysis toward water.The main research contents include:（1）Micro-alloying with vacuum induction melting furnace to prepare ternary alloy with atomic ratio of Mn₇₀Cu_30-xNi_x（x=0,1,3）.Then,dealloying treatment to selectively dissolve Mn element is performed to form porous CuNi precursor with different porosities.Followed by that,the porous CuNi electrode is hydrothermally sulfurized to obtained nanoparticles with a large specific surface area in situ on the surface of porous channel ligament.XRD,SEM,TEM and XPS results show that the active site is mainly single crystal polyhedron Cu₂S.Electrochemical results reveal that,S-np-Cu29Ni1 electrode has the best catalytic performance toward water electrolysis in 1.0 M KOH solution.When the current density drives a high current density of 100 m A cm^-2 in the process of hydrogen evolution（HER）,it only needs an overpotential of 173 m V.Moreover,only an overpotential of 356 m V is required to reach 100 m A cm^-2during the oxygen evolution（OER）reaction.It also possesses excellent stability and durability in the process of water electrolysis.The excellent catalytic performance is attributed to the large specific surface area owing to the multi-level pore structure and the electron transport channels,as well as the alloying effect deriving from the bimetallic active sites.（2）In this section,Al is used as the active component to produce ternary Al-Ni-Cu alloy（Ni/Cu atomic ratio is 1:1,1:2,2:1）ribbon in vacuum induction apparatus.Followed by partial dealloying and hydrothermal sulfurization treatment,a self-supporting electrode consisting of Al-doped S-np-NiCu bimetallic sulfides was prepared.Microstructure characterization shows that with the change of Ni/Cu atomic ratio,an obvious structural evolution from a uniform nanosheet to nanoplate occurs,greatly contributing to the increasement of the active specific surface area of the electrode.The electrochemical performance in 0.5 M H₂SO₄ solution depicts that when the Ni/Cu atomic ratio is 2:1,the current density of the self-supporting S-np-Ni21Cu7 electrode reaches50 m A cm^-2 under an overpotential of merely 245 m V.The Tafel slope of the corresponding electrode is fitted to 65.2 m V dec^-1,indicating fast kinetics for hydrogen evolution reaction.Meantime,the S-np-Ni21Cu7 electrode also exhibites excellent stability and durability in long-term water electrolysis process.