Design Of A New Two-Dimensional Polarized Porous Photocatalyst And Applications In Photocatalytic Water Splitting

Using solar energy to photocatalytic water splitting to produce hydrogen,and converting solar energy into hydrogen energy for storage is a promising method to solve the energy crisis.The existing two dimensional（2D）photocatalysts cannot effectively solve the problem of the accumulation of protons（H⁺）and hydroxyl（OH^-）ions on the two respective surfaces generated by the oxidation and reduction reactions,which results in normal photocatalytic water splitting reaction not being able to continue and the reaction is stopped.This paper fully grasps the current development trend and difficulties faced by photocatalytic water splitting research.By using first-principles calculation,predict and design a series of novel metal-free two-dimensional polarized porous photocatalysts.The discovery of metal-free porous photocatalysts not only reduces the cost,but also greatly expands the research scope of photocatalytic water splitting.Meanwhile,the porous nature of this material also solves the problem that the valence band（VB）and conduction band（CB）can continue to produce H₂ and O₂ during the process.The main research contents are as follows:（1）By density functional theory（DFT）calculation,we predict and design a series of novel stable metal-free porous material,including porous carbon（N-diaphene）and porous boron nitride（BN）materials.The thermodynamic stability,electronic band structure and optical properties of these materials were also studied.Finally,the photocatalytic water splitting performance of porous BN materials is mainly studied.（2）The two-dimensional porous BN was demonstrated to water splitting by infrared and visible light to produce hydrogen.The porous nature of two-dimensional BN guarantees the sustainability of the photocatalytic system and improves the efficiency of photocatalytic water splitting.By changing the number of layers and surface passivation of two-dimensional hexagonal BN,we can largely adjust the electronic properties including surface electrostatic potential and band gap.Which affects the material’s absorption range of the spectrum and the hydrogen production capacity of water splitting.The calculation results show the two-dimensional porous BN has good infrared and visible light absorption properties,the solar-to-hydrogen（STH）efficiency of F（BN）₃H,F（BN）₄H,H（BN）₃H,and H（BN）₄H are larger than10%,which breaks the conventional theoretical efficiency limit.Excitingly,the total energy conversion efficiency of H（BN）₄H using the solar energy of the whole solar spectrum to convert into hydrogen is up to 16.2%.Indicating the two-dimensional porous BN material is a potential metal-free photocatalyst for water splitting.