Preparation Of Transition Metal Chalcogenides Based Heterojunctions And Their Photoelectric Study

Photocatalytic techn ology is capable of using photocatalysts to convert solar energy into chemical energy efficiently,the technology reacts at room temperature to produce hydrogen,reduce carbon dioxide to alleviate or partially solve the energy crisis problem,and also degrade pollutants such as organic dyes and heavy metal ions to achieve self-cleaning and improve the problem of environmental pollution effectively.Two-dimensional materials as photocatalysts have the following advantages:i)They have a suitable band gap width and adjustable band gap,and can absorb light in most of the wavelength bands of the solar spectrum;ii)They have a large specific surface area,which is conducive to improving the light absorption rate;iii)They have a special microscopic layered structure with excellent carrier mobility and carrier dynamics,thereby increasing the transport rate of photogenerated carriers.Therefore,two-dimensional materials have been widely studied by scholars and are considered to be photocatalysts with good catalytic activity in recent years.Transition metal chalcogenate compounds(TMDCs)are among the most popular two-dimensional materials,the most representative of which are molybdenum disulfide(MoS2)and rhenium disulfide(ReS2).In this thesis,we have studied the photoelectrochemical properties of MoS2 and ReS2,and the structure of the semiconductors was changed by constructing MoS2 and ReS2 matrix heterojunctions respectively,and their photocatalytic activity could be improved by this way.The main work is as follows:(1)Preparation of ReS2/graphene heterojunction photoanode and its optoelectronic properties study:ReS2/graphene heterojunction photoanodes were produced,and the photoelectric properties of ReS2/graphene heterojunction photoanodes with different stacking structures were studied by changing the electrophoretic deposition sequence.Based on this,the maximum photocurrent density of ReS2/graphene heterojunction photoanode reaches 2.47 μA/cm2,which is 6.7 times and 2.1 times that of single graphene photoanode and ReS2 photoanode,respectively.The heterojunction of graphene on top and ReS2 below is different from the photocurrent density of the ReS2 photoanode,which is nearly 3 times larger than the heterojunction of another stacking structure.The study of heterojunctions with different stacking structures provides new ideas for the study of heterojunction structures,and promotes the conversion efficiency of optoelectronic devices.(2)Preparation of ReS2/Ti3C2 heterojunction photoanode and its optoelectronic properties study:ReS2/Ti3C2 heterojunction photoanodes of different mixing ratios were prepared by liquid phase peeling method combined with one-step electrophoretic deposition method.The maximum photocurrent density of the ReS2/Ti3C2 heterojunction photoanode is 5.98 μA/cm2,which is 12.7 times and 1.5 times that of the pure Ti3C2 photoanode and The ReS2 photoanode,respectively.By analyzing the ultraviolet-visible absorption spectrum,electrochemical impedance spectrum,and Mott-shottky curve,it is shown that the improvement of photoelectric response performance is mainly due to the superior electronic conductivity and metal properties of Ti3C2,with strong light absorption and effective charge transmission at the interface.By doping non-noble metal conductors in ReS2 in a low-cost and high-efficiency manner,it provides an effective method for improving the photoelectric response performance of two-dimensional optoelectronic devices.(3)Preparation of MoS2/Ti3C2 heterojunction photoanode and its optoelectronic properties study:First,MoS2 nanosheets of different sizes were prepared by gradient centrifugation,and the photoelectric response performance of MoS2 is the best when the centrifugal speed was 2000 r/min.MoS2 and Ti3C2 are selected to construct a heterojunction at a centrifugal speed of 2000 r/min.,and their photoelectrochemical properties were studied.At the ratio of MoS2/Ti3C2(1:1),the photocurrent density is further improved by about 3.4 μA/cm2,which is 1.7 times and 3.4 times that of single MoS2 and Ti3C2,respectively.The experimental results show that suitable size design and rational layered structure control are effective methods to enhance the photoelectric response of the photoelectrode.