Investigation On Electronic Structure And Photocatalytic Performance Of Two-Dimensional Chalcogenide Compounds And Their Composites

Environmental pollution and energy scarcity are two important issues facing the development of society and human survival.The development of pollution control technologies and the search for green new energy have been highly valued by people.Photocatalytic technology has shown great potential in utilizing solar energy to decompose aquatic hydrogen and degrade pollutants,which has attracted wide attention from scientists all over the world.Compared with the traditional pollution degradation method,photocatalysis technology has the advantages of high efficiency,green and no secondary pollution,and is the most potential environmentally friendly technology.In order to realize the industrial application of photocatalytic technology,the key is to develop a new high-efficiency photocatalyst.A semiconductor heterojunction is a combination of two or more semiconducto r materials that are optimally combined to form a composite material that not only maintains the superior properties of the components but also achieves their synergistic optimization performance.In this paper,the electronic structure and optical propert ies of two-dimensional chalcogenide compounds and their composites?such as WS₂/TX₂CO₂?TX=Ti,Zr?and GaS/GaSe heterojunctions?were studied by first-principles calculation.The results are as follows:?1?The electronic structure and optical properties of the two-dimensional layered nanomaterials WS₂,Ti₂CO₂,Zr₂CO₂ and WS₂/TX₂CO₂ heterojunctions were systematically calculated.Studies have shown that compared to single-layer materials,the two-dimensional WS₂/TX₂CO₂ heterojunction changes the band structure and the bandgap decreases due to the coupling between the interface atoms.The small bandgap allows the WS₂/TX₂CO₂ heterojunction composite to extend the corresponding range of the spectrum to the entire visible region,even the infrared region,thereby increasing solar energy utilization.The interface formed by by WS₂ and TX₂CO₂ is a type II heterojunction,which are beneficial to the separation of photogenerated electron and hole,thereby improving the photocatalytic efficiency.In addition,compared with the WS₂/TX₂CO₂-II heterojunction,the WS₂/TX₂CO₂-I heterojunction has stronger interfacial interaction,adsorption energy,charge transfer and stability,indicating that the properties of the composite are closely related to the way of stacking and appropriate materials,and it is also important to select appropriate materials and stacking mode.These results provide a new perspective and insight for the application of 2D TMDs and MXenes composites in the field of photocatalysis,and also provide a theoretical reference for the design and development of new 2D heterojunction composites.?2?The effects of interface on the electronic structure,charge transfer and optical properties of two-dimensional layered chalcogenide GaS/GaSe vdW composites were investigated.The calculation results show that the GaS/GaSe vdW heterojunction composite has smaller band gap?1.40 eV and 1.44 eV?and the interface forms a type II heterojunction,which is beneficial to improve solar energy utilization and photocatalytic quantum efficiency.In addition,compared with the WS₂/TX₂CO₂-II heterojunction,the WS₂/TX₂CO₂-I heterojunction has stronger interfacial interaction,adsorption energy,charge transfer and stability,indicating that the properties will be different with different stacking modes despite the same materials.This provides a reference for us to design and construct a new two-dimensional heterojunction composite,and also provides a theoretical basis for the application of two-dimensional chalcogenide in the field of photocatalysis.