Synthesis And Performance Of Mselenide(M=Nickel,Cobalt,Molybdenum) And Its Composites

Nowdays,as the reserve of traditional energy sources becomes more tense and environmental pollution becomes more serious,hydrogen energy has received wide attention as a new and clean energy source.The hydrogen produced by electrolyzed water has the advantages of abundance and high purity,and has broad application prospects.However,the large-scale application of this method in industry is greatly restricted by the need to use very rare precious metal platinum catalysts.Therefore,research and development of a low-cost catalyst that can be used in industry on a large scale has become a research hotspot in this field.This thesis intends to improve the catalytic activity of the transition metal selenide with a highly conductive carbon material by using a spray drying method.Firstly,the composite modification of carbon nanotubes（CNT）with single transition metal group selenide catalysts was studied.Then the composite modification of CNT with cobalt/molybdenum bimetallic selenide catalysts was studied.Finally,the composite modification of graphene and dextrin to cobalt/molybdenum bimetallic selenide catalysts was studied.The main research contents and conclusions are as follows:1.Through the spray drying process and subsequent selenization process,pure NiSe₂,CoSe₂,MoSe₂ and their CNT composites were prepared.Their hydrogen evolution reaction performance was tested.The results show that the catalytic activity of all samples has been greatly improved after CNT composite,especially the nickel diselenide/carbon nanotube composite（NiSe₂/CNT）,whose Tafel slope is only 29 mV dec^-1,which is almost the same as the commercial Pt/C material.It also has excellent stability.The improvement in catalytic performance is mainly due to the introduction of CNT,which weakens the agglomeration phenomenon in the material growth process,and greatly increases the electrochemical active area and conductivity of materials.2.Cobalt/molybdenum bimetallic selenide composite carbon nanotubes（CoSe₂-MoSe₂/CNT,abbreviated as CS-MS/CNT）were prepared by spray drying and subsequent selenization,and their hydrogen evolution reaction performance was studied.Compared with CoSe₂/CNT,MoSe₂/CNT and CoSe₂-MoSe₂ materials prepared under the same conditions,CS-MS/CNT composite have the best hydrogen evolution reaction efficiency,with a Tafel slope of 40.9 mV dec^-1 and an onset potential of-164 mV.The excellent hydrogen evolution reaction properties of CS-MS/CNT materials are attributed to the unique growth mechanism of bimetallic selenides and the introduction of highly conductive carbon nanotubes,which reduce the aggregation and increase the conductivity.3.Co/Mo bimetallic selenide composite graphene and dextrin composite（CoSe₂-MoSe₂/rGO-C,abbreviated as CS-MS/rGO-C）were prepared by spray drying and subsequent selenization process.Compared with CoMoO₄,CoSe₂-MoSe₂,CoSe₂-MoSe₂/C and CoSe₂-MoSe₂/rGO materials prepared under the same conditions,CS-MS/rGO-C has better hydrogen evolution reaction efficiency in both 0.5 M H₂SO₄and 1 M KOH electrolytes.In 0.5 M H₂SO₄ electrolyte,the Tafel slope of CS-MS/rGO-C composite is 51.3 mV dec^-1,the onset potential is-195 mV,the double-layer capacitance value is 6.49 mF cm^-2,and the electron transfer resistance is65.8Ω.In 1 M KOH electrolyte,the Tafel slope of CS-MS/rGO-C composite is 83.2mV dec^-1,the onset potential is-215 mV,the double-layer capacitance value is 1.62mF^-2,and the electron transfer resistance is 55.7Ω.The excellent properties are mainly attributed to its unique hollow porous spherical structure constructed by dextrin and the introduction of graphene,which not only increases the electrochemical active area of the material,but also enhances the conductivity of the material.