| As intermittent renewable energy sources are rapidly developing and gaining popularity,there is a growing demand for affordable and efficient energy storage technologies.Hydrogen is the most promising clean energy source for future energy carriers,and the electrolytic water to hydrogen production process is green and sustainable,with abundant raw materials that can achieve true zero carbon emissions.As the most effective electrocatalytic hydrogen precipitation（HER）catalyst,platinum（Pt）-based noble metal catalysts can catalyze the occurrence of electrolytic water reactions at conditions very close to the thermodynamic theoretical potential.However,precious metal resources are scarce and expensive to support the development of large-scale electrolytic hydrogen production technology.Therefore,there is an urgent need to develop and prepare efficient and inexpensive non-precious metal catalysts for hydrogen production from electrolytic water.Two-dimensional（2D）layered transition metal sulfides,especially molybdenum disulfide（Mo S2）,exhibit high catalytic activity for hydrogen precipitation and have attractive prospects as hydrogen precipitation catalysts.However,Mo S2 is a semiconductor with poor electrical conductivity and few edge sites as active sites for hydrogen precipitation,which largely limits the electrolytic water precipitation performance of Mo S2.The preparation of Mo S2 with many active sites and good electrical conductivity becomes the key to promote the application of such non-precious metal hydrogen precipitation catalysts.The photochemical process is quite different from the conventional thermochemical process,which usually has mild reaction conditions and forms species such as photo-living radicals to trigger unique reaction pathways and reaction kinetics,which are expected to form nanomaterials with unique structures and properties for material preparation.Therefore,in this thesis,Mo S2 nanostructures were prepared by photochemical method,and the transition metal doping and modulation of the photochemical reaction process were used to obtain highly active Mo S2-based catalysts for hydrogen precipitation from electrolytic water.The details of the study and the results are as follows:（1）Molybdenum disulfide with 1T/2H mixed phase structure was prepared by photochemical method using ammonium tetrathiomolybdate as the precursor reactant,and transition metals（Fe,Co,Ni）were introduced in situ,and experimental results demonstrated that the addition of metallic cobalt salts resulted in the formation of Co S2/Mo S2 composite catalyst,in which Co S2 could significantly reduce the interfacial charge transfer resistance of the composite catalyst,and the interaction between Co S2 and Mo S2 interaction leads to the increase of 1T-Mo S2 content,the increase of conductivity and the number of active sites of the composite catalyst,and the electrochemically active surface area of the optimized composite catalyst is nearly 16 times higher than that of commercial molybdenum disulfide,which significantly improves the HER catalytic activity of the Co S2/Mo S2 composite catalyst.At present,the stability of this Co S2/Mo S2 composite catalyst is poor,and it was found that the easy shedding of Co S2 from the Mo S2 surface is the main reason for the decrease of catalyst activity.（2）During the photochemical synthesis,the kinetics of the reduction of Mo6+by photoliving species and its binding with S2-will seriously affect the formation of Mo S2 and its structure.Therefore,in order to improve the Mo6+rate and regulate the kinetics of Mo S2synthesis,Mo S2 catalysts containing sulfur defective sites were synthesized by photochemical method using ammonium tetrathiomolybdate and ammonium molybdate tetrahydrate as precursors,and the electrocatalytic HER activity was significantly increased by modulating the ratio of the two and the amount of sacrificial agent.The electrochemical HER performance test results of the optimized sample Mo S2-UV-100-S40 showed that the overpotential of Mo S2-UV-100-S40 at 10 m A cm-2 was only 293 m V with a Tafel slope of 42 m V dec-1. |
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