Preparation And Properties Of MoS₂/VO₂ Nanocomposites

Molybdenum disulfide is a new two-dimensional layered structure of transition metal sulfides.It has large specific surface area,and the exposed edge structure has active site that adsorbs hydrogen atoms,which can reduce the activation energy of the electrochemical reaction and accelerate the electron transfer rate.Therefore,it can be used as catalyzer in electrochemical reactions.However,the common MoS₂ exhibits low conductivity and a small number of active sites which limit its application in catalysis.How to design the exposure of more active sites and enhance the transfer rate of effective charge has become the focus of research.In addition,providing enough electrons from the electrode to active sites is equally important for increasing the number of exposed active sites,the transfer of proton/electron is directly related to the efficiency of the hydrogen evolution of the electrocatalysis system.Mechanical deformation is an effective method of supplying electrons to the active site of the catalyst.In this paper,The main method of preparing MoS₂/VO₂ heterojunction composite is hydrothermal method.Firstly,VO₂ nanorods with good phase transition properties were prepared and then composited with MoS₂ nanosheets to form heterostructures.It can be used to study the effect of phase transition properties of VO₂ on the electrocatalytic hydrogen evolution behavior of MoS₂/VO₂heterostructures.The specific research content is as follows:?1?Preparing VO₂ nanorods by hydrothermal method.The effects of reaction temperature and tungsten doping content on the phase and growth morphology of VO₂were investigated.The electrical properties of tungsten doped VO₂ nanorods by using PPMS and DSC.The results show that the phase transition temperature is about 52?,and the resistivity decreased after the phase change by two orders of magnitude.?2?MoS₂/VO₂ hybrids were prepared by hydrothermal method.The growth behavior of MoS₂ nanosheets on tungsten-doped VO₂ nanorods was investigated by adjusting the H₂SO₄ concentration and the MoS₂ content.The study found that the MoS₂/VO₂ hybrid?MoS₂ content 60%?grown in 45 mM H₂SO₄ had the best morphology.The XPS test results show that the MoS₂/VO₂ hybrids material has a lower valence shift than the pure MoS₂ nanosheet with a valence band offset of about0.2 eV.MoS₂ forms a heterostructure with VO₂,which can facilitate the transfer of effective electrons in the MoS₂/VO₂ hybrid.?3?The electrocatalytic hydrogen evolution performance of the MoS₂/VO₂heterostructure was tested by an electrochemical workstation.Tests show that samples treated by H₂SO₄ exhibit enhanced hydrogen evolution performance in all samples.Among them,45-MoS₂/VO₂?MoS₂ content is 60%?hybrid has the best HER performance,with an onset potential of 188 mV and a Tafel slope of 93 mV/dec.The enhanced hydrogen evolution performance is mainly due to the existence of rich active sites at the treated interface,while the synergy between MoS₂ and VO₂accelerates the electron transfer rate.In addition,upon the phase transition of VO₂,its onset potential and Tafel slope decreased to 99 mV and 85 mV/dec,respectively.This is attributed to the enhanced charge transfer efficiency and the effect of interfacial strain on the change of the electronic structure of MoS₂.