Preparation And Electrochemical Activities For Hydrogen Evolution Of 1T Phase Of Molybdenum Disulfide

Hydrogen is widely regarded as an ideal clean energy carrier for energy conversion and storage.Hydrogen production from electrolysis of water is a sustainable method of hydrogen production.Platinum-based catalysts are highly efficient hydrogen evolution catalysts with almost zero overpotential.However,due to their high price and scarcity,their large-scale applications are greatly limited.Therefore,it is necessary to develop low-cost,high-efficient non-noble metal-based catalysts.Nanostructured molybdenum disulfide（Mo S₂）is a good non-platinum based hydrogen evolution catalyst because of its low cost and high efficiency.Among them,the catalytic active sites of 1T-Mo S₂ are not confined to the edge of Mo S₂,and its active sites on the basal surface are also activated.However,the 1T phase is highly unstable and can be easily transformed into a more stable 2H phase.Therefore,it is very important to make the 1T phase stable without the phase transition.In this thesis,the stable 1T-Mo S₂ was prepared by solvothermal method.The structure,morphology and formation mechanism of the prepared materials were analyzed,and the catalytic properties of 1T-Mo S₂ for hydrogen evolution were investigated.The main contents and results of this paper are as followed:1.RGO-assisted one-pot hydrothermal synthesis was adopted to modulate the metallic 1T phase and 2H phase of Mo S₂ simultaneously.The content of 1T phase in Mo S₂/RGO-180 composites was found to be up to 80%.It also showed excellent electrocatalytic activity.The overpotential was 213 m V（vs RHE）at a current density of-10 m A cm^-2.The Tafel slope was 43 m V dce^-1.After 90 days,the sample did not undergo phase transition and the performance did not show significant attenuation because the interaction between RGO and Mo S₂ could prevent the phase transition of1T-Mo S₂.2.The loosely and ordered assembled MoO₃ was prepared by hydrothermal method,and the assembled 1T-Mo S₂ was obtained after sulfuration.Additionally,sulfuration did not change the morphology.The influence of the relative catalytic activity of the assemblages and crystals were investigated.The content of the 1T phase in the assembled 1T-Mo S₂ was found to be 78%by XPS characterization.The assembled1T-Mo S₂ not only fully exposes the edge active sites,but also activates the active site of the base surface at the same time because of the formation of the 1T phase,and thus has better catalytic performance for HER.The overpotential was 196 m V（vs RHE）at a current density of-10 m A cm^-2.The Tafel slope was 48 m V dce^-1.After 90days,the assembled 1T-Mo S₂ did not undergo phase transition and its performance was not significantly attenuated because the assembly played a crucial role in achieving the stability of 1T-Mo S₂.3.Using the prepared Mo-MOF as the precursor,α-MoO₃ was formed through calcining,and on this basis,it was sulfided by a hydrothermal method to obtain1T-Mo S₂.The octahedral coordination of MoO₃ facilitates the direct formation of the same octahedral coordination 1T-Mo S₂ after sulfuration.The morphology,structural composition and electrocatalytic hydrogen evolution reaction of 1T-Mo S₂ were studied.1T-Mo S₂ exhibited excellent electrocatalytic activity.The overpotential was256 m V（vs RHE）at a current density of-10 m A cm^-2.The Tafel slope was 58 m V dce^-1,and the overpotential(-10 m A cm^-2)was only increased by 9 m V after 1000cycles,indicating good stability.After 90 days,1T-Mo S₂ did not undergo phase transition and its performance was not significantly attenuated.