Preparation And Properties Of Electrocatalytic Hydrogen Evolut Ion Materials Based On Group ⅥB

In order to make up for the scarcity and expensiveness of noble metal electrocatalysts,as well as the defects of low electrical conductivity,poor stability and corrosion resistance,the research direction is aimed to the study the preparation and hydrogen evolution performance of VIB electrocatalyst materials.In this dissertation,this kind of catalyst was prepared by the common hydrothermal method,microwave method,ultrasonic method and microwave high-pressure ultrasonic three synergistic methods.By elemental doping,modifying conductive carbon materials,and adjusting the proportion of transition metal elements,the electrical conductivity of this type of electrocatalyst could be improved to increase specific surface area,thereby improving its electrocatalytic water splitting performance.The elemental structure of the electrocatalyst was analyzed by X-ray diffractometer,X-ray photoelectron spectroscopy and Raman spectroscopy;The morphology was characterized by field emission scanning electron microscopy and transmission electron microscopy;Electrocatalysts were characterized for a series of their electrochemical performance.Taking the research in this paper as an example,it could provide a certain value for the improvement of water electrolysis of the VIB electrocatalyst.1.Microwave hydrothermal synthesis of Ce-doped composites of molybdenum selenide and carbon nanotubes（MoSe₂@CNTs）as an efficient non-noble metal electrocatalystThe authors doped MoSe₂@CNTs transition electrocatalysts with cerium with different cerium-molybdenum ratios through the synergistic method of microwave hydrothermal stirring,and this catalytic material showed good performance in both acidic and alkaline electrolytes.The electrocatalytic hydrogen evolution performance,especially in the ratio of Ce:Mo（1:5）,showing the best electrochemical activity and long-term stability in acidic alkaline electrolyte,which was 108 mV and 166 mV at current density of 10 mA/cm²,respectively.Due to the layer-by-layer MoSe₂structure,combing of MoSe₂and CNT,the as-prepared electrocatalysts exhibited effectively increased active sites for electrocatalytic reactions and accelerated charge transfer from the active site to the conductive carbon nanotubes.And this study provided a reference opportunity for the design and fabrication of efficient catalysts with multiple synergistic effects.2.Microwave-ultrasonic synergistic synthesis of MoS₂electrocatalyst for hydrogen evolutionThe MoS₂electrocatalyst was prepared by the ultrasonic/microwave synergistic method,and the effects of power density and reaction time on the morphology and hydrogen evolution performance of MoS₂electrocatalyst were investigated.The microwave radiation heating is beneficial to refine the MoS₂electrocatalyst precursor particles in a large area and improve the dispersion degree between the particles.At the same time,the chemical effect of ultrasonic waves could provide sufficient energy for the ions to be nucleated in the reaction solution to promote the MoS₂electrocatalyst.At the same time,the cavitation and mechanical effects of ultrasonic waves could play a better stirring effect,and its strength was far greater than that of ordinary stirring,which hinders the growth of MoS₂electrocatalyst particles with high efficiency,and the length of the reaction time.The nucleation and growth of monolayer MoSe₂grains were effectively controlled.The three parts of work together obtained the electrocatalysts with small particle size,good dispersion and complete structure.Under the optimal parameter selection,MoS₂electrocatalyst had excellent hydrogen evolution performance and long-term stability in acidic and alkaline electrolytes.The overpotentials were 176mV and 154 mV at 10 mA/cm²,respectively.3.Molybdenum-doped composites of nickel carbide and carbon nanotubes（Ni₃C@CNT）electrocatalyst performance for water splittingA method for the preparation of molybdenum-doped Ni₃C@CNT electrocatalysts with different concentrations using Ni-MOF solution as precursor solution,ammonium molybdate tetrahydrate and p-phenylenediamine as raw materials was studied.The obtained electrocatalysts exhibited good oxygen evolution and hydrogen evolution activity in both simulated seawater electrolyte and alkaline electrolyte.The electrochemical test results showed that the molybdenum doping concentration of 1%showed better electrochemical activity than other samples.In the alkaline electrolyte,The overpotential for oxygen evolution were 202 and 198 mV at a current density of 10 mA/cm²in the alkaline electrolyte and simulated seawater electrolyte,respectively.Through systematic testing and characterizations,it was found that the improved HER and OER electrocatalytic activities of the catalyst were derived from the intense interaction between the carbon nanotubes and Ni-based catalyst and the synergistic effect.In addition,the Mo-doped N_i3C@CNT electrocatalysts could increase the active sites and conductivity of N_i3C@CNTs.