First Principles Investigation On The Regulation Of Electronic And Photocatalytic Properties Of Two-dimensional Materials

With the advent of the‘Post-Moore’era,the electronic properties of two-dimensional materials cannot fulfill all the requirements of nano electronic device materials in the future,such as spin electronic devices that can be applied in the field of magnetic storage.At the same time,with the increasingly serious environmental pollution,the use of low-dimensional materials for photocatalytic decomposition of water to produce renewable green energy is an important way to achieve carbon neutralization.Therefore,it is of great significance for human development to regulate the photoelectric properties of two-dimensional materials and design new materials with specific uses.Based on the first-principles calculations,the electronic and optical properties of two-dimensional materials are regulated through reasonable material design,such as doping and adsorption,construction of van der Waals heterostructures,construction of new Janus materials,etc.the specific research contents are as follows:（1）Adsorption is one of the effective means to control the electronic properties of low-dimensional semiconductor materials.Black phosphorene and arsenene doped with transition metals show unique electronic properties.Pristine black phosphorene and arsenene have no magnetism.After doping with transition metals,Fe-,Co-,Au-black phosphorene and Ti-,Cr-,Ni-arsenene turn out to be magnetic semiconductors.Moreover,the black phosphorene and arsenene system doped with transition metal elements has the potential to catalyze the oxidation of carbon monoxide after adsorbing a single O₂ molecule.This provides a new idea for us to manufacture low-cost carbon monoxide catalyst and application in spintronics.（2）At present,the research on improving the electronic properties of Mo Si₂N₄ by molecular adsorption is relatively scarce.Here,TCNQ and TCNE are selected as electron acceptors and TTF as electron donor.Theoretical calculation shows that Mo Si₂N₄ becomes an effective p-type semiconductor with band gaps of 0.15 e V and 0.11 e V after adsorbing TCNQ and TCNE,respectively.While adsorbed TTF,the case becomes an n-type semiconductor with band gap of 0.56 e V.The applied electric field effectively regulates the carrier injection concentration of the adsorption system,which greatly improves the performance of Mo Si₂N₄in nano-electronic devices.（3）Van der Waals heterostructures Mo S₂/Mg（OH）₂,WS₂/Mg（OH）₂,Mo S₂/BSe,WS₂/BSe,Mo SSe/Blue P were designed.The theoretical results show that the formed heterosteuctures are type II heterosteucture,which all exhibit potential photocatalytic ability to decompose water.In addition,the van der Waal heterstructures based on transition metal sulfides also show better photoelectric properties than the component materials,without changing the electronic properties of the component materials.For example,Mo SSe/Blue P has an energy conversion efficiency of 19.9%at 2%strain.Heterostructure with good stability and excellent photoelectric properties provides an inspired idea for designing efficient photocatalytic materials.（4）Janus materials Pd₄S₃Se₃,Pd₄S₃Te₃ and Pd₄Se₃Te₃ have been designed.The materials have excellent kinetic and thermodynamic stability,and show high carrier mobility and solar-to-hydrogen evolution efficiency,breaking the limitation of traditional photocatalytic materials that the band edge numerical difference is greater than 1.23 e V.This work provides a brand-new idea for designing new photocatalyst.