The Preparation And Electrochemical Hydrogen Evolution Properties Of Transition Metal Compounds

As one of the most important means to generate the clean energy H2,electrochemical decomposition of water has attracted widespread attention in society and has been studied in depth.Catalyst is a crucial factor in the efficiency of hydrogen production.Due to their unique structure and electronic properties,layered transition metal compounds have been extensively studied for their controllable hydrogen evolution properties.In this paper,a simple hydrothermal method and a systematic chemical vapor deposition were used to synthesize the corresponding compounds on metal substrates.The experimental results show that the catalysts with high hydrogen evolution activity can be obtained by proper regulation of the growth conditions.Firstly,the MoS2 thin films with large specific surface area were prepared on Mo foil by hydrothermal method,and there were sulfur vacancies in the products.To further enhance the activity of MoS2 films,the electrochemical deposition method was used to decorate platinum nanoparticles on the surface.Theoretical and experimental results indicate that the HER performance of synthesized MoS2 films with S vacancy can be further enhanced by the slight addition of Pt decoration,which can introduce new gap states and more catalytic sites in real space with suitable free energy.The resulted Pt/MoS2/Mo hybrid electrocatalyst exhibits apparent hydrogen evolution activity with an onset potential close to 0 V and a small overpotential of only 58 mV to produce a current density of 10 mA/cm2.Then we studied the catalytic activity of WS2 which has similar properties to MoS2.The vertical ultrathin WS2 nanosheets that have a large specific surface area were grown on W foil by chemical vapor deposition.There were lots of stepped structures and exposed edge sites due to the difference of WS2 layer in various regions,some defects also exist on the basal plane,besides.All these factors can contribute to the improvement of the catalytic hydrogen evolution performance of WS2.The onset potential of the product is about 30 mV,and an operating potential of only 106 mV for 10 mA/cm2.On the basis of the previous work,we adopted chemical vapor deposition to synthesize the composite material as electrocatalyst.The Mo2C/MoSe2 composite on Mo foil was obtained by oxidation,selenization and carbonization of Mo foil in sequence.The electrochemical hydrogen evolution performance test results showed that the composite catalyst had excellent hydrogen evolution performance under both acidic and basic conditions.The onset potentials of catalyst in acidic and basic electrolyte are about 48 mV and 0 V,respectively,and the overpotential of 98 mV and 43 mV are needed when the current density achieve 10 mA/cm2.