Preparation And HER Performance Of MXene Supported Composite Electrocatalysts

As the energy crisis of traditional fossil fuels and the global climate change caused by carbon emissions have received increasing attention,the development of environmentally friendly and sustainable clean energy has become a hot spot for people’s attention.Hydrogen energy has the advantages of high energy density,abundant reserves,sustainability and zero emissions after combustion,so it is considered to be the most promising alternative energy source for fossil fuels in the future.In recent years,hydrogen production by electrolysis of water has attracted more and more attention from academia and industry due to its advantages such as large hydrogen production,high purity,no carbon emissions,strong sustainability,and abundant water resources.The hydrogen evolution process requires highly efficient HER catalyst to accelerate the reaction kinetics and improve HER activity.As we all know,the precious metal platinum（Pt）has the best intrinsic catalytic activity for HER,but its low platinum reserves,high cost,and poor stability severely hinder its large-scale industrial application.Therefore,it is of great practical significance to search for high-efficiency,low-cost,and durable non-Pt electrocatalysts.Choosing a good support material to increase the loading of the catalyst can effectively increase the number of catalytic active sites,which is very important for improving the electrocatalytic activity.In this paper,the two-dimensional transition metal compound MXene（Ti₃C₂）is selected as the conductive substrate,and nanofibers and carbon nanotubes are innovatively introduced to prepare composite carrier,combined with relatively low-cost transition metal compound molybdenum disulfide or bimetallic ruthenium（Ru）and cobalt（Co）.The catalytic materials with high hydrogen evolution performance are prepared by impregnation-ultrasonic,vulcanization reduction,high-temperature carbonization,etc.The main contents are as follows:（1）The PAN fiber membrane obtained by electrospinning is placed in the MXene（Ti₃C₂）dispersion liquid,and a highly dispersed continuous MXene composite membrane material with a fiber skeleton structure（Ti₃C₂@PAN）is prepared by the immersion-ultrasonic method.This paper systematically studies the influence of the mass percentage concentration of Ti₃C₂dispersion and the immersion ultrasonic time on the framework structure,and determines the best conditions for preparing Ti₃C₂@PAN.Under these conditions,Ti₃C₂@PAN materials with clear skeleton structure and complete lamella structure can be obtained.In addition,its surface resistance is only increased by 2.3Ω/sqr compared with pure Ti₃C₂（3Ω/sqr）,which shows it still maintains good electrical conductivity.（2）On the basis of the previous research work,this paper selects Ti₃C₂@PAN as the carrier,and prepares the fiber skeleton MXene material loaded with molybdenum disulfide nanosheets by sulfide reduction molybdenum salt and high-temperature carbonization,The influence of the content of molybdenum salt and the carbonization temperature on the structure and performance of the catalyst is also studied.The results show that the electrocatalyst（Mo S₂/Ti₃C₂@CNFs-0.2-900）has good catalytic activity and stability in 0.5 M H₂SO₄ electrolyte.At the current density of 10 m A·cm^-2,the hydrogen evolution overpotential(η₁₀)of the catalyst is 142 m V,and the corresponding Tafel slope is 113 m V·dec^-1.The hydrogen evolution overpotential of the catalyst is 76.17%lower than that of molybdenum disulfide catalyst,and its catalytic activity is obviously improved.The framework support and synergistic carrier of the fiber greatly increase the loading of molybdenum disulfide,promote uniform loading,and greatly increase the number of catalytic active sites.At the same time,the chemical coupling between molybdenum disulfide and the carrier gives the catalyst excellent stability.（3）In order to further improve the electrocatalytic performance,an electrocatalyst supported by bimetallic nanoparticles is designed and synthesized.Nanotubes are selected as carbon-based materials to prepare composite carrier CNTs@Ti₃C₂.Ruthenium salt and cobalt salt are introduced to prepare CNTs@Ti₃C₂ electrocatalyst loaded with cobalt and ruthenium bimetallic nanoparticles under high temperature conditions.The influence of the ratio（ruthenium salt and cobalt salt）and carbonization temperature on morphology and performance is explored.Studies have shown that the catalyst（Co Ru/CNTs@Ti₃C₂-900-0.3）has lower hydrogen evolution overpotential(η₁₀=74 m V)and Tafel slope(80 m V·dec^-1)in acid electrolyte（0.5 M H₂SO₄）and excellent stability.The composite structure of CNTs@Ti₃C₂ reduces the agglomeration of CNTs and the stacking of Ti₃C₂ sheets,and promotes the uniform dispersion of cobalt ruthenium nanoparticles on the carrier,thereby exposing more active sites.These characteristics make Co Ru/CNTs@Ti₃C₂ exhibit excellent electrocatalytic hydrogen evolution performance.