Structure Design,Controlled Synthesis And Electrocatalytic Performance Modulation For W/Mo-Based Nanostructure Catalysts

With the rapid development of industrial economy,the modern society faces the dual pressure of energy shortages and environmental pollution,so exploitation and utilization of new and sustainable energy has received attention.As a new type of renewable energy with high calorific value,renewable,zero emission and high utilization rate,hydrogen has been considered a most promising clean and environmentally friendly energy sources.Electrolytic hydrogen evolution reaction has become one of the most ideal ways to solve energy problems due to its high efficiency and high hydrogen purity.Nevertheless,the sluggish electrode reaction kinetics and high cost block its rapid development.To improve the efficiency of electrolytic water hydrogen evolution,it is crucial to exploit electrocatalysts with high activity,high stability and low cost.The transition metals tungsten and molybdenum have been widely studied due to its high content in the crust,low cost,good electrical conductivity,high carrier transfer rate,etc.However,the morphology regulation and surface modification of tungsten/molybdenum-based catalysts in electrocatalytic hydrogen evolution still need to be solved urgently,as well as designing an easy large-scale synthesis method to maintain the high catalytic activity and high stability of the catalysts.Based on the structural design and controllable synthesis strategies（morphology regulation,doping,defect engineering and heterostructure construction）,several tungsten/molybdenum based electrocatalysts with high activity,high stability and low cost were prepared in this paper.It provides a new theoretical basis for the large-scale use of tungsten/molybdenum-based electrocatalysts in energy conversion.The main research results are as follows:（1）We employed an economical,environmentally friendly,and facile pyrolysis method to prepare a novel ruthenium（Ru）-transition metal carbide(WC_1-X)nanoparticles catalyst,which uniformly distributing and firmly embedded into the urea-derived highly porous nitrogen-doped carbon framework.The morphology,structure,and surface properties were characterized by a series of physical tests.The results indicated that the Ru and WC_1-Xsynergistic effect and the enhanced conductivity were main reasons for improving HER performance.In particular,Ru/WC_1-X@NC exhibits excellent electrocatalytic performance for HER under alkaline conditions,reaching a current density of 10 m A cm^-2with only a low overpotential of 24 m V in 1 M KOH,the Tafel slope of 45 m V dec^-1,as well as shown good electrocatalytic hydrogen evolution performance in neutral and acidic solutions.The Ru/WC_1-X@NC electrocatalyst has a relatively low cost and exhibits excellent electrochemical HER performance comparable to commercial Pt/C,indicating that the catalysts is one of the ideal substitutes for commercial Pt/C.（2）Based on the morphology regulation and heterojunction construction,we synthesized an electrocatalyst-WP/Mo P with excellent performance in both acidic and basic solutions by a simple solid-phase method.The morphology,structure and surface characteristics were tested by XRD,SEM,HRTEM and XPS,etc.The results found that the addition of W not only modulates the catalyst morphology,making it from irregular nanoparticles into 20μm nanorods.The as-prepared WP/Mo P nanomaterials also exhibit highly efficient and stable electrocatalytic hydrogen evolution performance with an overpotential of 138 m V at-10 m A cm^-2and Tafel of 114 m V dec^-1in alkaline solution,the overpotential of 193 m V at-10 m A cm^-2and 104 m V dec^-1of Tafel in acidic solution.After 20 h stability test in acidic or alkaline solution,the current density did not decrease significantly,indicating its durable catalytic performance and structural stability.The excellent electrocatalytic performance of the catalyst may be attributed to the formation of a heterostructure,and the heterointerface is more favorable for electron transfer and material transport,thereby enhancing its electrocatalytic efficiency.This research has the advantages of simple synthesis method,environmentally friendly,and inexpensive,which provides a new attempt to design other heterojunction electrocatalysts.（3）A low-cost and high-performance Mo S₂-based HER catalyst was prepared by a simple etch-ultrasonic process.Two-dimensional Mo S₂flakes were obtained by an expandable top-down exfoliated method from natural molybdenite,and the electrocatalytic hydrogen evolution performance was improved.The overpotential was 274 m V at-10 m A cm^-2and Tafel was 154 m V dec^-1in alkaline solution,the overpotential was 346 m V at-10 m A cm^-2and Tafel was 180 m V dec^-1in acidic solution.In particular,few-layered Mo S₂can be prepared by acid etching and isopropanol ultrasonic treatment,with an overpotential of 142m V in alkaline solution and 300 m V in acidic solution both at-10 m A cm^-2.Most importantly,this simple and controllable preparation process enables laege-scale production,which provides new opportunities for other two-dimensional electrocatalytic materials in energy conversion research.