Preparation And Photocatalytic Performance Investigation Of Layered MoS₂/Cu₂O Composites

Molybdenum disulfide is a layered transition metal chalcogenide with typically layered graphene structure. Two-dimensional MoS₂ is a typical two-dimensional material. When the three-dimensional material become into two-dimensional material, due to the strong anisotropy, the quantum size effect and the rapid increase in the specific surface area, MoS₂ have a unique mechanical, optical, electrical, energy storage, catalysis and gas sensing properties, having broad research value in electronic devices, optics, solid lubricants, catalysts, ultra-capacitors, lithium batteries and other fields. Mo S2 is abundant, inexpensive and suitable for industrial mass production in recent years. Band structure of the MoS₂ semiconductor varies with the layers, which can follow our willingness to purposefully control MoS₂ layers for the appropriate band, having a broad research value and application.Due to the semiconductor properties, band controll ability, a large number of active sites of two-dimensional MoS₂, it has widespread concern on the photoelectrochemistry area,especially on the photocatalytic area. Monolayers MoS₂ has a 1.8eV suitable band gap to absorb visible light, the direct band gap structure being conducive to electronic transitions, more strong active dangling bonds, but its preparation and low activity limits its development. MoS₂ is currently widely used as a co-catalyst or composite semiconductor in efficient photocatalytic reaction, but the efficient alone MoS₂ remains to be studied. Compound semiconductors have advantages for its effective separation of electron-hole pairs and the higher the photocatalytic activity. Its design and preparation is the key to find the two or more right semiconductor material which requires the band structure of semiconductor material to match with each other. They can form a heterojunction between the surfaces of the material and have a large number of active sites. Two dimensional MoS₂ have large specific surface area, suitable energy band structure, a lot of unsaturated active sites as being a n-type semiconductor characteristics itself. Cu₂ O is a p-type semiconductor and can respond to visible light. They can well be compound semiconductors. Therefore, it is imperative to look for a simple, easy, inexpensive, gentle preparation method which can purpose fully control level match and form more heterojunction between the two semiconductors for highly active photocatalyst. It has very important guiding meaning for design, basic research and practical applications of highly active photocatalyst. We design and prepare a high active photocatalytic coupled semiconductor by improving our photocatalytic degradation experiment using compounds emiconductor.（1）Based on the principle of improving the photocatalytic activity of compound semiconductors,we uesed hydrothermal synthesis method to grow Cu₂ O nanoparticles on MoS₂ nanosheets to form MoS₂/Cu₂ O. By comparing the photocatalytic activity of fewer-layer MoS₂, Cu₂ O and MoS₂/Cu₂ O, we verify the design rationality of photocatalyst.（2）Based on the relevant contact of photocatalytic activity and heterojunction of MoS₂/Cu₂ O, we prepare MoS₂/Cu₂ O with the same component content by chemical synthesis and physical synthesis, exploring the effect of heterojunction on photocatalytic activity and the effect of preparation method on the formation of the heterojunction.（3）Based on the relationof MoS₂ band gap width and the band potential with its layers, we peel off bulk Mo S2 into MoS₂ suspension with different thickness by liquid exfoliation and gradient centrifugation methods. With the thickness of Mo S2 reduce, the area increases, the band gap becomes larger, the band potential increases, redox potential of photogenerated electron-hole pairses increase. MoS₂/Cu₂ O with the different thickness of MoS₂ are prepared by hydrothermal synthesis and explore the relationship of photocatalytic activity and thickness of Mo S2.（4）Based on known the optimum thickness of MoS₂ of MoS₂/Cu₂ O, we explore MoS₂ content of MoS₂/Cu₂ O which affect the photocatalytic activity. The results show an increasing content of MoS₂ increase heterojunction formation and improves the photocatalytic activity, but too much MoS₂ will reduce its photocatalytic activity.（5）Based on（3） and（4）, the relatively highest photocatalytic activity MoS₂/Cu₂ O is acquired. Their photocatalytic cycle stability and photocatalytic reduction of heavy metal ions have a comparison between MoS₂/Cu₂ O and Cu₂ O. The results show that MoS₂/Cu₂ O is better than Cu₂ O on the stability and the ability of reducing the heavy metal ions.