Preparation Of WC/C Nano Catalyst And Its Electrocatalytic Performance For Hydrogen Evolution

Hydrogen energy is a kind of clean energy with high combustion calorific value.The research,development and utilization of hydrogen energy is of great significance to solve the increasingly serious problems of energy shortage and environmental pollution.Electrolyzed water is one of the most effective methods to prepare hydrogen.It has aroused great interest of researchers to explore efficient and cheap electrocatalysts to reduce the hydrogen evolution overpotential of electrolyzed water,thereby reducing energy consumption and improving the efficiency of hydrogen evolution reaction.Tungsten carbide based electrocatalyst has been proved to have good electrocatalytic activity for hydrogen evolution due to its similar d-band electron density state with Pt.However,there are still some problems in the preparation process,such as the larger particle size of WC catalyst,the easier agglomeration of WC catalyst,the lower catalytic activity and the higher W-H bond binding energy.In order to solve these problems,nanostructured nitrogen sulfur doped tungsten carbide nanoparticles were designed to inhibit particle aggregation,increase the contact surface between electrolyte and electrode materials,expose more active sites,and optimize the electronic structure of tungsten carbide,so as to improve its electrocatalytic hydrogen evolution performance.The details are as follows:（1）WC/C composite catalysts were prepared by one-step carbonization of glucose and ammonium tungsten（AMT）in molten salt.The effects of carbonization temperature,mass ratio of salt to sugar,mass ratio of tungsten source to carbon source on the structure,microstructure and hydrogen evolution performance of the catalyst were studied.Furthermore,dicyandiamide and cysteine were added as nitrogen and sulfur sources to explore the effects of nitrogen and sulfur doping on the structure,microstructure and hydrogen evolution performance of the composite,and finally reveal the key factors affecting the electrocatalytic activity.The electrochemical test results show that the n-s-doped WC/C electrocatalyst has excellent HER performance.In 0.5 M H₂SO₄solution,the required overpotential is 112 mV and the Tafel slope is54.4 mV/dec when the current density is 10 mA/cm².Moreover,the electrocatalyst has remarkable long-term electrocatalytic stability.The Tafel slope is 68.8 mV/dec in1 M KOH solution,and the required overpotential is 122 mV when the current density is 10 mA/cm².It also has significant long-time electrocatalytic stability in 1 M KOH solution.This method can be used to synthesize other transition metal carbides instead of platinum based catalysts.（2）Using biomass pomelo peel powder as carbon source,AMT as tungsten source and glucose as carbon source,the biomass carbon based composite catalyst material（WC/C）with tungsten carbide nanoparticles loaded on carbon sheet was prepared by one-step carbonization in molten salt under the same process parameters.Furthermore,dicyandiamide and cysteine were added as nitrogen and sulfur sources to explore the effects of nitrogen and sulfur doping on the structure,microstructure and hydrogen evolution performance of the composite,and finally reveal the key factors affecting the electrocatalytic activity.The results of electrochemical tests show that the biomass carbon based n-s-doped WC/C electrocatalyst has excellent HER performance.When the current density is 10 mA/cm²,the required overpotential is158 mV and the Tafel slope is 68 mV/dec.The new hydrogen evolution catalyst was successfully prepared by replacing the traditional carbon source with biomass carbon source.