First-principles Study Of Photocatalysts For Water Splitting

In recent years,since the environmental pollution and energy crisis have become more and more serious,people are eager to obtain a new type of pollution-free energy to replace non-renewable fossil fuels such as coal and oil.And hydrogen energy is undoubtedly our best choice.So far,the reaction of the red-hot carbon with the water vapor and the methane CN₄ purified from the natural gas and petroleum reacting with the water vapor have been two main ways to produce the hydrogen H₂ in the industries.In addition,the photolysis of water is produced to be a cleaner and cheaper way to produce hydrogen.And the first breakthrough was that in 1972 Fujishima and Honda used TiO₂ electrodes to achieve the complete decomposition of water.Since then,people have opened the door to the research on the use of various semiconductor materials as photocatalytic materials to produce hydrogen.In this paper,we mainly investigate the possibility of two two-dimensional materials acting as catalysts for photo-hydrolytic hydrogen production by using density functional theory?DFT?.On the one hand,by studying the electrical and optical properties of two-dimensional?2D? nonmetallic nano-film g-HTAP,we found that it has good structural stability and optical absorption efficiency.By simulating the g-HTAP in the hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?,we found that the two-dimensional film has good hydrogen production performance,while the driving force of oxygen evolution process is slightly insufficient,which can ensure the smooth progress of hydrogen production by adding sacrificial agents.On the other hand,we also investigated the photocatalytic properties 2D hetero-junction materials PtS₂/MoSe₂.Because some photocatalytic materials may only satisfy the hydrogen evolution or oxygen evolution reaction,it is impossible to realize the whole photolysis water process.For example,MoSe₂ is a good hydrogen evolution material but not a good oxygen evolution material.We have found an oxygen evolution material PtS₂,which has only 3%mismatch rate with MoSe₂.Based on the idea of heterojunction devices,we can design them to form a van der Waals type hetero-junction PtS₂/MoSe₂.Through studying the electrical and optical properties of PtS₂/MoSe₂ hetero-junctions,we find that PtS₂/MoSe₂ hetero-junctions belong to z-type hetero-junctions,and their optical absorption efficiency is significantly higher than that of the components.The energy level of the z-type hetero-junction completely covers the redox potential of water,which can be used for photolysis.