Preparation Of Ruthenium Selenide-based Nanocomposites And Their Performance Of Electrocatalytic Hydrogen Evolution

Hydrogen（H₂）is the molecule with the highest energy density per unit mass.Although the hydrogen element is abundant on Earth,the reserves of free hydrogen molecules are quite limited.Efficient and sustainable production is the key to the widespread utilization of H₂.Electrocatalytic water splitting technology,which can utilize electricity generated from intermittent renewable energy sources to produce hydrogen,has shown great promise in large-scale and green hydrogen production.Currently,platinum group metals are considered to be the best electrocatalysts for hydrogen evolution reaction（HER）.However,the high cost and limited reserves of these materials hinder their widespread application.For mass production of H₂ via electrocatalytic water splitting,low-cost and abundant Pt substitutes must be found.Besides noble metals,transition metal selenides（TMSs）are also the most studied HER catalysts.Among different types of materials,TMSs have outstanding catalytic properties,high stability,and unique ability to accelerate HER.In fact,TMSs have similar structures to the corresponding sulfides,but with higher electrical conductivity,which is due to the fact that Se is more metallic.Therefore,TMSs are an ideal class of HER electrocatalysts for efficient water electrolysis.At present,the main methods for the modification of TMSs electrocatalysts include phase transition and interlayer engineering,alloying,element doping,heterojunction,and composite nanostructures.In this paper,RuSe₂ nanomaterials were prepared by microwave-assisted reduction and hydrothermal co-reduction,and phase transition control,Co,N-doped carbon nanosheets（Co-N-C）and reduced graphene oxide（r-GO）were used.The composite method improves its performance.Through the morphology structure and electrochemical characterization,the reasons why the modification method improves the electrocatalytic HER performance are discussed.The main contents are as follows:（1）Using Se powder and Ru Cl₃ as raw materials and ethylene glycol as dispersant,a 1T and 2H mixed phase RuSe₂ electrocatalyst with high crystallinity was prepared by microwave-assisted reduction method and used for electrocatalytic hydrogen evolution in alkaline solution.By controlling the annealing temperature,the content and crystallinity of 1T phase in RuSe₂ were synergistically adjusted.When the annealing temperature is 500°C,RuSe₂-500has a 1T phase content of 45.46%and a crystallinity of 86.75%,and also has the best HER performance,with an overpotential of only 29 m V at a current density of 10 m A cm^-2.The Tafel slope is 64 m V dec^-1.The high 1T phase content enhances the electrical conductivity,accelerates the electron transfer rate,and the increase in crystallinity also increases the electrochemically active specific surface area,so RuSe₂-500 has the best HER performance.（2）In this part,we use Co-N-C as a catalyst support to form a heterostructure with RuSe₂ by a hydrothermal method and use it for electrocatalytic hydrogen evolution in alkaline solution.After loading on Co-N-C,the HER performance of RuSe₂ is significantly improved.The overpotential of RuSe₂/Co-N-C-5 is only 26.4 m V at a current density of 10m A cm^-2,and the Tafel slope is 53.2 m V dec^-1.It has a stability of 17 h at a current density of m A cm^-2.This is mainly due to the fact that the Co-N-C substrate is suitable for exposing more active centers and has better electrical conductivity.The doping of Co and N also endows the carbon nanosheets with additional water adsorption and dissociation functions.Benefiting from the synergistic effect induced by Co functionalization and unique heterointerface to enhance the HER performance of RuSe₂.（3）Preparation of RuSe₂/r-GO composites and study of alkaline electrocatalytic HER performance.Using a hydrothermal co-reduction method,graphene oxide was reduced and composited with RuSe₂ nanoparticles for HER in alkaline solution.The effect of the addition of graphene oxide on the HER performance of RuSe₂/r-GO was also investigated.Among them,the overpotential of RuSe₂/r-GO-5 in alkaline solution at a current density of 10m A cm^-2 is only 35.5 m V,and the Tafel slope is 56.1 m V dec^-1.Long-term cycling tests and chronoamperometry tests also show that it has lasting stability.After RuSe₂ was coupled with r-GO,the defect-rich r-GO provided a large number of active sites for RuSe₂ and enhanced the electrical conductivity,thereby enhancing the intrinsic electrocatalytic hydrogen evolution activity of RuSe₂.