Study On The Electronic Properties Of MoSSe Nanotube And Planar Antimonene

Recently,low-dimensional materials,due to their excellent physical and chemical properties,have shown tremendous application potential in various field.Among them.photocatalyst has become an effective solution for current worldwide energy crisis and environmental pollution problem.Compared with traditional three-dimensional system,those low-dimensional materials possess higher specific surface area,higher carrier mobility and more easily tunable chemical properties,which could improve solar to hydrogen(STH)conversion efficiency,thus they are very promising in photocatalytic application.However,the recombination rate of electron-hole pairs in low-dimensional materials is still too fast to meet the photocatalytic requirement,thus it is still necessary and urgent to investigate new photocatalyst with high efficiency.On the other hand,the precondition of practically applying those low-dimensional materials is preparing high-quality ones.Substrate is essential during preparation and application.Suitable substrate can not only provide support to ensure experimentally preparation of them with high quality and large area,but also protect their electronic structure from substrate itself.Therefore,finding suitable substrate for low-dimensional materials is even as important as finding excellent low-dimensional materials themselves.In this thesis,we study the electronic properties of two low-dimensional materials(Janus MoSSe nanotube and planar antimonene monolayer),discuss the photocatalytical potential of MoSSe nanotube,and provide two suitable inert substrates for planar antimonene.The dissertation falls into five chapters.The first chapter outlines a brief introduction of the state of research and development of low-dimensional materials.The second chapter focuses on the theoretical methods and computational codes based on density functional theory and time-dependent density functional theory.In the third chapter,we systematically research the electronic structure and electron-hole recombination dynamics of Janus MoSSe nanotube.In the fourth chapter,for the lack of suitable substrate for planar antimonene,we discuss the influence that three substrates have on planar antimonene.Finally,we summarized the main conclusions and innovations of this dissertation,followed by an outlook for the future of the research field in the fifth chapter.The main work and results are listed as follows:(1)Transition metal sulfides have shown huge potential in photocatalytic application Here,based on the time-dependent density functional theory and nonadiabatic molecular dynamics,we propose that one-dimensional Janus MoSSe nanotube is a promising photocatalyst with high catalytic efficiency.Our results show that the Janus MoSSe nanotube possesses suitable direct band-gaps and appropriate band edge positions that perfectly meet the requirements of water redox reactions.In particular,it exhibits pronounced optical absorption in the visible region of the solar spectrum.Most importantly,due to the built-in electric field,an ultra-long carrier lifetime of 33 ns has been observed,which is comparable to that of TiO2.Such extremely long carrier lifetime can efficiently reduce the recombination rate of photogenerated electrons and holes,leading to high solar energy conversion efficiency.These advanced properties make the Janus MoSSe nanotube a promising candidate for further water splitting applications.The work provides theoretical basis for experimentally developing new photocatalyst with high efficiency(2)Planar antimonene,as one of the most promising two-dimensional materials,was recently obtained on a Ag(111)substrate.However,its particular electronic properties are severely degraded due to the substrate,making its further study and practical applications challenging.Here,using first-principles calculations,we propose that h-BN and hydrogenated SiC(00001)are extraordinary substrates of planar antimonene.Their interactions with planar antimonene exhibit low binding energies and large interlayer distances,and are typical van der Waals interactions Most importantly,the bands of planar antimonene near the Fermi level are perfectly preserved,with the bands of h-BN and hydrogenated SiC(00001)lying away from the Fermi level.Moreover,such features are inert to the stacking patterns for both systems,making them suitable for practical applications.Our results thus provide ideal platforms for observing the intriguing electronic properties and topological phenomena in planar antimonene,thus greatly broaden its scientific and technological impact.