First-Principles Study Of Photocatalytic Properties Of Three Van Der Waals Heterostructures:GaN/InS,GeC/PtSe₂ And PtS₂/g-C₃N₄

Inrecent years,due to the intensification of environmental pollution and energy crisis,renewable green energy has gradually become the focus of current research.Solar energy and hydrogen energy are harmlessness and safety among many renewable green energy sources,and are considered the most important and ideal green energy.Based on this,the use of solar photocatalytic water splitting to produce hydrogen has attracted great interest from academia and industry and is considered to be one of the most feasible industrial production methods.Two-dimensional semiconductor materials are widely used in the field of photocatalysis because of their unique photoelectric properties,but their photocatalytic activity is greatly reduced due to their shortcomings such as high carrier recombination rate and poor optical performance.Therefore,the photocatalytic process of splitting water requires suitable structures,such as van der Waals（vd W）heterostructure.Inthis paper,based on first-principles calculation,the structural stability,carrier migration mechanism,photoelectric properties,and photocatalytic mechanism of GaN/InS,GeC/PtSe₂,PtS₂/g-C₃N₄ vd W heterostructures have been systematically studied.The main research results are as follows:（1）The structure and electronic properties of monolayer GaN and InS materials are analyzed,and the GaN/InS vd W heterostructure is constructed.The geometry,photoelectric properties and photocatalytic mechanism of the heterostructure are studied in detail.The results show that the GaN/InS heterostructure has an indirect band gap and type-II band alignment.And the band edge position of heterostructure meets the requirements of photocatalytic water splitting,which can effectively separate photogenerated carriers and improve their lifetime.Inaddition,due to the GaN layer is negatively charged and the InS layer is positively charged,the heterostructure interface is induced to generate a built-in electric field from InS to GaN,which inhibits the recombination of photogenerated carriers.Compared with its monolayer materials,the GaN/InS vd W heterostructure has better optical properties and solar-to-hydrogen conversion efficiency in the visible light region,effectively improving the utilization rate of solar energy.These excellent properties make the GaN/InS vd W heterostructure promising to be an efficient photocatalyst.（2）The monolayers GeC and PtSe₂ materials are analyzed and GeC/PtSe₂ vd W heterostructure is constructed.The structural stability,photoelectric properties and photocatalytic activity of the heterostructure are calculated and analyzed in detail.The results show that the GeC/PtSe₂ vd W heterostructure can exist stably at room temperature,and has a type-II band alignment and suitable band edge position,which meets the requirements of complete water splitting.Inaddition,the interface o the GeC/PtSe₂ vd W heterostructure forms a built-in electric field from GeC to PtSe₂,which induces the heterostructure to form a direct Z-scheme charge transfer mechanism,effectively improving the redox capacity.The direct Z-scheme GeC/PtSe₂ vd W heterostructure has excellent optical properties,high solar hydrogen conversion efficiency and efficient catalytic activity.These results show the GeC/PtSe₂ vd W heterostructure has broad application prospects as a complete water-splitting photocatalyst.（3）The monolayers PtS₂ and g-C₃N₄ materials are analyzed and the PtS₂/g-C₃N₄ vd W heterostructure is constructed.The geometry,photoelectric properties and photocatalytic mechanism of the heterostructure are calculated and analyzed in detail.The results show that the PtS₂/g-C₃N₄ vd W heterostructure has a type-II band alignment,and a built-in electric field from g-C₃N₄ to PtS₂ is formed at the interface,which induces the formation of a direct Z-scheme charge transfer mechanism in the heterostructure and is conducive to accelerating the migration of photogenerated carriers.At the same time,the PtS₂/g-C₃N₄ vd W heterostructure also has a good edge position,which is sufficient to induce the redox reaction of decomposed water.Compared with monolayers PtS₂ and g-C₃N₄,the PtS₂/g-C₃N₄ vd W heterostructure has better optical performance and solar hydrogen conversion efficiency.Inaddition,biaxial strain effectively improves the optical performance of the heterostructure and redshifts the spectrum.Finally,the calculation of free energy for redox reactions also shows that the heterostructure has high photocatalytic activity,which proves that the PtS₂/g-C₃N₄ vd W heterostructure can be used as a promising photocatalyst for hydrogen and oxygen production.