Preparation Of Co_xM_y(M=O,S)/Carbon Composite Material And Research On Electrocatalytic Hydrogen Evolution Of Material

Hydrogen is widely regarded as a new energy source with great application prospects because of its high combustion calorific value and environmental friendliness.As a method of preparing hydrogen,electrolyzed water has the advantages of high purity of hydrogen and no generation of by-products.If the problem of low efficiency of electrolyzed water can be solved,large-scale industrial electrolysis of water can be realized to produce hydrogen.In this paper,with the goal of developing electrocatalytic hydrogen evolution electrode materials with excellent research performance,two different cobalt based-carbon composite materials have been successfully prepared,and their microscopic morphology,phase composition and electrochemical performance have been analyzed and characterized.The specific research content is as follows:(1)A one-step high-temperature calcination method is used to prepare the electrode material of cobalt tetroxide loaded on nitrogen-doped carbon nanotubes(Co₃O₄-NCTs),and the catalyst is applied to the research of electrocatalytic hydrogen evolution in alkaline solution.Oxygen vacancies will cover electrochemically active sites and reduce the electrochemical performance of the material.Therefore,there are few reports on oxides in the field of hydrogen evolution in electrolysis of water.Based on this,the first experiment of this article studied the Co₃O₄ nanomaterials as the active center of the electrocatalyst,supplemented by the use of large surface area N-doped modified carbon nanotubes(NCTs)as the carrier,using its synergistic effect to increase the electrochemically active sites of the oxide.In order to examine the influence of heat treatment temperature on the prepared samples,this article carried out a series of characterization and analysis on samples at different temperatures.Scanning electron microscopy(SEM)and transmission electron microscopy(TEM)confirmed that the Co₃O₄-NCTs obtained at 700?had the best microscopic morphology,showing that Co3O4nanoparticles were uniformly loaded on carbon nanotubes.X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)confirmed that Co₃O₄ had been successfully synthesized.Raman and specific surface area analysis showed that the material The degree of graphitization and specific surface area.The electrochemicalresearch results showed that Co₃O₄-NCTs prepared at 700?have excellent electrocatalytic hydrogen evolution performance.Including ultra-low Tafel slope(32.3 m V dec-1,close to the theoretical limit),good stability(through 500CV cycles and 48 hours of I-T chronoamperometry test,Co₃O₄-NCTs curve change rate is still low),and relatively better turnover frequency(TOF,calculated by the BET method to obtain the highest TOF value of Co₃O₄-NCTs/700)and low charge transfer resistance R_ct.(2)CoS₂ quantum dots(CoS₂QDs)were prepared by sulfur modification with ZIF-67 as the precursor and loaded on reducing graphene oxide(r GO)to successfully prepare CoS₂QDs@r GO composite materials.The formation of ZIF-67 and quantum dots was confirmed by SEM and TEM.XRD and XPS confirmed that the quantum dots were CoS₂quantum dots.Raman demonstrated that graphene oxide was successfully reduced.CoS₂QDs@r GO has good electrochemical performance in alkaline solutions:to achieve a current density of 10 m A cm^-2,the overpotential required is 298 m V,the Tafel slope is 78 m V dec^-1and a relatively better electrochemical double-layer capacitor(C_dl,calculated by formula using CV curves obtained at different sweep speeds)and low charge transfer resistance R_ct.CoS₂QDs@r GO has such performance,we think it is because ZIF-67 is used as the material precursor.In each step of the reaction,the structure and size of the material are excellently controlled.Meanwhile,the organic combination of zero-dimensional materials and three-dimensional materials also effectively improves the electrocatalytic activity of the materials.In addition,compared with the traditional quantum dot preparation process,the method proposed in this experiment is simpler and more effective,allowing more routes for the preparation of quantum dots.