Theoretical Study Of The Regulation Of The Properties Of Photocatalytic Water Splitting In Two-Dimensional Materials By Interlayer Interaction

The use of solar energy for photocatalytic water splitting to alleviate deteriorating environmental problems has great potential.Two-dimensional（2D）materials have many advantages and have become extremely promising photocatalysts.For example,the band edge that can be adjusted has a larger specific surface area relative to the bulk systems,and shows more active sites in photocatalysis.Moreover,the photo-generated carrier migration distance of the two-dimensional material is shorter.These excellent characteristics have aroused widespread research interest.It is worth noting that the thickness of the two-dimensional material is an important factor that changes the physical and chemical properties,and the different stacking methods of the two-dimensional material have an important effect on the stability of the system.Coupling between layers plays an extremely important role in the physical and chemical properties of different two-dimensional materials,thereby adjusting their photocatalytic performance.In this thesis,density functional theory is used to study the photocatalytic properties of water splitting by studying the thickness of two-dimensional materials,stacking methods and heterostructures.The main research results are as follows:We systematically studied the influence of the thickness of Bi₄Ta O₈Cl on its photocatalytic oxygen evolution performance.Interestingly,we found that due to the interlayer coupling effect,the thin layer of Bi₄Ta O₈Cl has a more significant photocatalytic performance than the single layer of Bi₄Ta O₈Cl.Compared with the single-layer Bi₄Ta O₈Cl,the thin-layer has a wider light absorption range,a larger transition dipole moment,a stronger reduction potential used to drive the oxygen evolution reaction,and a lower recombination probability of photo-generated electrons and holes.The coupling interaction between the layers improves the photocatalytic performance,thereby promoting the progress of the two-dimensional material in the photocatalytic water splitting reaction.By studying the new two-dimensional material Si₂N₄Mo under different stacking methods,the most stable geometric structure was selected,and then the photocatalytic hydrogen evolution reaction was studied.In order to enhance the photocatalytic hydrogen evolution performance of the new two-dimensional material Si₂N₄Mo,we used two modification methods of N vacancy and B doping to systematically study the two-dimensional material Si₂N₄Mo.Studies have found that by introducing N vacancies into intrinsic Si₂N₄Mo or doping intrinsic Si₂N₄Mo with B,the photocatalytic hydrogen evolution catalytic activity of its two-dimensional materials has a significant enhancement effect.The calculation and analysis of the partial charge density distribution at the top of the valence band and the bottom of the conduction band show that the N vacancy has a significant enhancement effect on the hydrogen evolution reaction.For the intrinsic Si₂N₄Mo,the light absorption of the two-dimensional material doped with B and the Gibbs free energy of the hydrogen evolution reaction have been significantly enhanced.In turn,the photocatalytic performance of the Si₂N₄Mo hydrogen evolution reaction is enhanced.The basic properties of two-dimensional materials C₂N,C₃N,C₃N₄,C₃B and two-dimensional ferroelectric materials In₂S₃,In₂Se₃,In₂Te₃,Al₂S₃,Al₂Se₃,Al₂Te₃,Ga₂S₃,Ga₂Se₂,Ga₂Te₃ are systematically studied.Therefore,the type II ferroelectric heterojunction that can completely dissolve water is predicted,and then ferroelectric heterojunction C₃N₄/Al₂S₃ and C₃N₄/Al₂Se₃ are obtained.The two-dimensional ferroelectric heterojunctions C₃N₄/Al₂S₃ and C₃N₄/Al₂Se₃ have suitable energy band edges and partial charges at the bottom of the conduction band and the top of the valence band can be distributed on the upper and lower surfaces of the heterojunction.It greatly promotes the separation of photo-generated electron-hole pairs,and can also inhibit the recombination of photo-generated electrons and photo-generated holes.Moreover,the inherent ferroelectricity of the ferroelectric heterojunction itself has the same effect on the separation and recombination of photogenerated electrons and holes.And the huge photo-generated electron potential and photo-generated hole potential of the two-dimensional ferroelectric heterojunction can effectively promote the entire photocatalytic total water dissolution process.