A First Principle Design For The Two-Dimensional Semiconductor Photocatalysts

In recent years,photocatalytic technologies have gradually received attention in the fields of developing green energy and the fight against environmental pollution,but there are still several key problems including narrow solar spectral response range,low quantum efficiency,carrier recombination within the material,and weak surface reaction activity that restrict its development and application.Therefore,the development of new materials with a wide response range of the solar spectrum,fast carrier separation,and migration ability,and high catalytic activity plays an important role in the development of photocatalytic technologies.According to the advantages,of short carrier migration distance,high specific surface area,and easy-to-control electron properties,two-dimensional materials have become an ideal choice for constructing new photocatalyst systems.Theoretical design of high-efficiency two-dimensional photocatalysts to guide experimental preparation is increasingly important due to the improvement of theoretical calculation methods and the computer level.In this paper,we have systematically investigated the influence of heteroatom co-doping,element ratio modulation and heterostructure building strategies on the structural stability,electronic properties,light absorption properties and surface reactivity of several new two-dimensional photocatalysts based on the first principle calculations.The main research results are as follows:（1）The investigation of two co-doping strategies involes charge compensation（N+F）and double anion（N+P）on the photocatalytic performance of Janus monolayer Mo SSe.N+F co-doping is thermodynamically stable to be prepared in experiments,and also does not introduce the unoccupied intermediate states that can avoid the appearance of photo-generated carrier recombination centers.For the electron properties,N+F co-doping narrowed the band gap of the monolayer Mo SSe to 1.28～1.57 e V,and the visible light responding ability was enhanced.However,the strong redox ability to photocatalytic water-splitting was maintained due to the existence of the polarization electric field of the Janus monolayer material.Besides,N+F co-doped Mo SSe exhibits the excellent ability to hydrogen evolution reaction because of the ideal H*adsorption energy caused by the introduction of N atoms.（2）A theoretical study of monolayer In₂X₂Y（X/Y=S,Se,Te;X≠Y）photocatalyst.We built a series of In₂X₂Y configurations by replacing one of the surface X atomic layers in monolayer In₂X₃with the Y atomic layers.The stable monolayer In₂S₂Se in thermodynamic and kinetic with high-efficiency photocatalytic water oxidation performance was screened out.Although the band gaps of the two isomers produced by the different replaced atomic layers are2.29 and 1.21 e V,the polarizing electric field makes the requirement for straddling the water redox potential are met under the premise of the visible light response.The element Se leads to the reduction of the thermodynamic barrier in the oxygen evolution reaction so that both isomers can drive the oxygen evolution reaction to proceed spontaneously.In addition,the difference in the effective mass of photogenerated electrons and holes of the monolayer In₂S₂Se is larger than that of its parent material In₂S₃,which can further prevent the recombination of photogenerated carriers.（3）A theoretical research on direct Z-scheme Arsenene/SnSSe heterojunction.In order to utilize the advantages of the polarized electric field in Janus monolayer materials and the strong redox capability of the Z-scheme heterojunction,we selected the monolayer Arsenene and the monolayer SnSSe with similar lattice parameters and matching band energy levels to construct a heterojunction.The results suggested that the two heterojunctions formed by the different interface contact types can exist stably,and both have the characteristics of the Z-scheme heterojunction.The two heterojunctions have indirect bandgap structures of 0.53 and 0.80e V,respectively,and the absorption intensity for visible light and ultraviolet light is significantly enhanced after the formation of the heterojunction.In addition,the net electric field formed by the coupling of the built-in electric field and the polarization electric field origin from SnSSe runs through the entire heterojunction system and is still out-of-plane.No matter the stacking type,the direction of the net electric field always points to the side of the S atomic layer in SnSSe,which could reduce the recombination by promoting the separation and directional migration of photogenerated carriers in SnSSe and Arsenene.This work demonstrates the unique advantages of a Z-scheme heterojunction photocatalytic system with a polarizing electric field.