Study On MoS₂ And Its Composite For Enhanced Photo-and Electrochemical Hydrogen Evolution Reaction

As the environmental pollution and the energy crisis becomes more and more serious,people start to realize the importance of building a new renewable energy system with green and sustainable energy.Hydrogen,as a kind of clean and renewable energy,has entered into the horizon of people,and its simple and efficient preparation method has been a hot topic among scholars at home and abroad.Among them,photoelectricatalytic hydrogen evolution reaction,because of its simple reaction operation and high production efficiency,become an important way in hydrogen production.The catalyst is a significant portion of material in photoelectrocatalytic hydrogen evolution reaction,however,the low photoelectric conversion efficiency and low activity of the photoelctrocatalyst in hydrogen evolution reaction have been restricting the development photoelctricatalytic hydrogen production.Therefore,the development of photoelectrocatalyst which own a high activity,high light utilization,low cost for hydrogen production has become a research hotspot.Molybdenum disulfide catalyst,benefited by its special structure layer and the appropriate band gap,becomes a two-dimensional non-noble metal cathode catalysts and is expected to replace Pt-based catalysts.However,it still has some shortcoming for low visible light utilization,high carrier recombination rate and less active site.In order to solve these problems of molybdenum disulfide,we explored the preparation method of molybdenum disulfide,and designed two kinds of molybdenum disulfide composite system according to the different method and then investigated the photoelectricatalytic performance via the in-depth research.The research contents of this paper are as follows.1.Firstly,ZnO@MoS2 nuclear-shell nanorod array was prepared by hydrothermal method in which ZnO nanorod arrays were produced,and followed by electrodepostion of MoS2 at constant potential.And then,by Scanning electron microscope(SEM),transmission electron microscope(TEM)and the X-ray powder diffraction(XRD),we verify the nuclear-shell structure.UV-visible absorption spectra(UV-vis)and Photoluminescence(PL)experiment,indicate the expansion of the scope of its light absorption and light absorption,the light absorption and light-electric induction performance of ZnO@MoS2 have been greatly improved.Electrochemical measurements(cyclic voltammetry(CV),linear sweep voltammetry(LSV)and electrochemical impedance spectroscope(EIS)we found that the light induced current is up to 0.3076 mA cm-2 under 0 V bias.Besides,ZnO@MoS2 composite possess a graet electrochemical activity surface area(23.3 mF cm-2),which lead to the increase of reactive sites.the performance of photoelectric activity of hydrogen evolution finally has been further improved,and the overpotential decreased to 330 mV at current density of 10 mA cm-2 under under light illumination2.With ammonium molybdate as molybdenum source and sodium tungstate as tungsten source and L-cysteine as the source of sulfur,MoS2/WS2 nanocomposite is successfully synthesized by one-step microwave hydrothermal method on ITO glass.The structure of MoS2/WS2 composite has been investigated through HRTEM,XPS analysis,and we found that there are a few 1T-MoS2 phase,which result in the augment of active site in MoS2/WS2 composite.In addition,When the WS2 is introducted and uniform distribute in MoS2,it become a heterjunction,which will help to speed up the carrier transmission,thus improve the photoelectrocatalyst activity of hydrogen evolution reaction.On the basis of the previous step,we fabricated different MoS2/WS2 heterostrucutures which are decorated with Bi2S3 nanorods through different stacking sequences(MoS2/WS2(bottom layer)+Bi2S3(top layer)and Bi2S3(bottom layer)+MoS2/WS2(top layer),respectively).Scanning electron microscope(SEM),transmission electron microscope(TEM)and the X-ray powder diffraction(XRD)indicate that the hybrid structure with different stacking sequences of composite structure are composed of Bi2S3 nanorods and MoS2/WS2 nanosheet.By UV-visible absorption spectra(UV-vis)and Photoluminescence(PL)experiment,we found that both of the different stacking sequences of composites can promote visible-light utilization and accelerate the electron transportation.Electrochemical measurements(cyclic voltammetry(CV),linear sweep voltammetry(LSV)and electrochemical impedance spectroscope(EIS)under light illumination or in dark)indicated that the MoS2/WS2+Bi2S3 possessed higher photoelectrocatalytic activity towards HER than that of Bi2S3+MoS2/WS2 due to its proper energy band alignment that facilitates the effective carrier separation,the lower charge transfer resistance,higher electrochemically active surface area as well as the fast electron transfer kinetics.Inspired by those observations,we believe that MoS2/WS2+Bi2S3 is a potential candidate photoelectrocatalyst for production of H2.