Construction And HER/OER Electrocatalytic Performance Of Ru(Ir) Decorated Nickel Selenides

As a simple and environment-friendly technology for hydrogen production,water electrolysis is a significant way to realize the goal of“carbon peak and carbon neutral”.However,hitherto,the best hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）catalysts are precious metals such as Pt and Ir O₂（Ru O₂）,which seriously restrict the application and development of hydrogen production technology.Therefore,there is an urgent need to develop catalysts with low content of precious metals and high catalytic activity in HER and OER,promoting the hydrogen production technology.As the semiconductor material,nickel selenides（Ni_xSe_y）,with a narrow band gap and unique electronic structure,become a research hotspot in the field of electrocatalysis.Nevertheless,the electrocatalytic performance is severely limited by low density of active sites.Thus,researchers are dedicated to stimulating the electrocatalytic activity of nickel-based selenide catalysts for efficient water electrolysis to produce hydrogen.In this thesis,the structure of Ni Se₂ is optimized by using a variety of efficient modification strategies.Transition metal selenides decorated with ultralow content of Ru/Ir are synthesized,and the electrochemical properties for HER/OER are tested in alkaline electrolyte.The main research contents are listed as follows:1.Density Functional Theory（DFT）calculations demonstrate that the incorporation of Ru optimizes the adsorption free energy of water molecules and intermediates during HER/OER（^*H,^*OH,^*O and^*OOH）on the Ni atoms,thereby effectively promoting the catalytic kinetics of HER and OER.Under the guidance of this result,the electrode,with ultra-low ruthenium（Ru）decorated nickel selenide nanosheets structure（Ru-Ni Se₂/NF）,is constructed on the three-dimensional conductive substrate nickel foam（NF）by using the“hydrothermal,impregnation,selenization”method.The electrode maintains the excellent three-dimensional nanosheet array structure of the precursor,which can provide enough electrochemical specific surface area and guarantee the exposure of amounts of active sites,available for the boosting of the catalytic activity.It is indicated by the electrochemical test in 1M KOH that the Ru-Ni Se₂/NF electrode merely requires OER and HER overpotentials of 210 and 59 m V,respectively,to obtain the current density of 10 mA cm^-2.In addition,when used as both anode and cathode for overall water splitting in alkaline electrolytes,the voltage of 1.537 V is only needed to drive the current density of 10 mA cm^-2,with excellent stability for 65 h,which is better than most of the reported transition metal selenide catalytic materials.2.In order to prove whether the iridium-based substances have the similar modification effect to ruthenium,and to explore the growth characteristics of nickel selenides without structural induction,iridium（Ir）incorporated two-dimensional nickel diselenide nanoslices with edge-induced growth iridium selenide nanoparticles(Ir Se₂/Ir_xNi_1-xSe₂ NSs/CC)is constructed on the flexible substrate carbon cloth（CC）with the same method as the aforementioned work.The special structure that endows the catalyst system with the larger active surface area and large number of active sites exposed,as well as the synergistic influence of intra-surface doping and nanoparticles around the edge,conducive to promote the electrochemical reaction kinetics.By the electrochemical test in 1 M KOH,it is illustrated that the Ir Se₂/Ir_xNi_1-xSe₂ NSs/CC electrode can drive current densities of 10 and 100 mA cm^-2 with OER overpotentials of merely 220 and 276 m V,respectively.Meanwhile,due to the regulation of Ir atoms in the catalyst system,the synthesized electrode possesses ultra-high stability.It can maintain the current density of nearly 120 mA cm^-2 for 200 h.