| With the growth of economy,the demand for traditional fossil energy and excessive consumption of fossil fuels have brought about various environmental pollution problems and energy crisis,which have caused serious damage to economic and social development.The emergence of these problems urgently urges people to develop environmentally friendly and sustainable new energy sources.Among them,hydrogen has attracted much attention because of its high combustion heat,no pollution to the environment and wide sources.Among many hydrogen production technologies,the preparation of hydrogen from electrolytic water is considered to be one of the effective hydrogen production technologies because of its simple operation and pollution-free advantages.At present,platinum-based precious metals have the best performance among many hydrogen evolution catalysts,but their large-scale application is limited by their low natural reserves and high prices.Transition metal sulfides have become a hot research in recent years due to their abundant natural resources and low price.Molybdenum disulfide(Mo S2),a typical representative of transition metal sulfides,has excellent electrocatalytic hydrogen evolution performance.However,molybdenum disulfide,as a semiconductor material,has poor conductivity and is easy to agglomerate,which reduces the active sites of hydrogen evolution,which is not conducive to its electrocatalytic hydrogen evolution performance.In the field of hydrogen evolution,graphene has been extensively studied for its good conductivity and large specific surface area,which provides a good platform for the synthesis of hydrogen evolution catalysts with excellent conductivity.Therefore,in order to improve the existing problems of molybdenum disulfide,a series of research work has been carried out around transition metal sulphide materials in order to synthesize transition metal sulphide composites with good conductivity and few and single layers.It mainly includes the following two parts:1.Ni S2/MoS2-RGO nanocomposites with nanorod structure were successfully synthesized by solvothermal method and high temperature vulcanization.The electrocatalytic hydrogen evolution properties of Ni S2/Mo S2-RGO nanocomposites were investigated in the whole p H range.Specific research contents are as follows:Ni Mo O4-RGO,a precursor,which was synthesized by using the mixture of secondary water and anhydrous ethanol as solvent and graphene oxide as the base of rod-like nickel molybdate.Ni Mo O4-RGO and sublimated sulfur were evenly mixed at 1:20 and vulcanized at high temperature to obtain the target material,named Ni S2/Mo S2-RGO.The hydrogen evolution performance of the composite was investigated by electrochemical test.The electrochemical test results showed that the composite Ni S2/Mo S2-RGO exhibited excellent electrocatalytic performance as an electrocatalyst in the whole p H range(acidity,alkalinity and neutrality).When the p H of the electrolyte solution is 0,7 and 14,the current density of Ni S2/Mo S2-RGO reaches 10 m A/cm2in the process of hydrogen evolution.The overpotential of Ni S2/Mo S2-RGO is 172 m V,144m V and 229 m V,respectively.The slope of Tafel is 51 m V/dec,82 m V and 103 m V/dec,respectively.The successful preparation of the composite and the hydrogen evolution reaction in the whole p H range provide us with a new application idea.2.Nickel nanoparticles were synthesized by hydrothermal method and chemical reduction method and loaded on molybdenum disulfide and graphene oxide composites(Ni-Mo S2/RGO).The presence of nickel nanoparticles makes molybdenum disulfide have more defective structures,which is conducive to the exposure of more active sites.The electrochemical hydrogen evolution of the obtained composite was tested in 0.5 M H2SO4medium.The analysis showed that the overpotential required for the material to reach current density of 1 m A/cm2 was 146 m V,and the smaller Tafel slope was 65 m V/dec.The mechanism of the electrocatalytic hydrogen evolution reaction of the material was revealed to be Volmer-Heyrovsky.After 8 h stability test,the activity of hydrogen evolution reaction did not decrease obviously,which showed that the material had excellent cyclic stability. |
PDF Full Text Request