Fabrication And Photoelectric Performance Of ?Sb,N? And ?C,S? Codoped SnO₂ Based On Density Functional Theory

The problems of energy insufficiency and environmental disruption become more and more critical with the consumption of fossil energy.Solar energy utilization and carbon dioxide conversion by photoelectric catalysis are effective ways to solve the above problems.SnO₂ is a key material for solar energy utilization and carbon dioxide conversion because of its high electron mobility,good chemical stability and low preparation cost.However,the band gap of pure SnO₂ is wide and its carrier recombination rate is high,which limits its application.In order to overcome these shortcomings,a large number of studies have reported that the band structure and carrier separation rate of SnO₂can be controlled by simple and controllable element doping method.The modified SnO₂ has good photoelectric performance and can be better applied in the field of photocatalysis.In order to improve the photoelectric performance of SnO₂,donor-acceptor pair doping and double-hole-assisited coupling doping were attempted.Firstly,?Sb,N?and?C,S?co-doped SnO₂ were designed by first-principle calculation.The electronic structure and photoelectric performance of the co-doped materials were investigated,and the mechanism of dopants in the two doping methods was discussed.At the same time,different ratios of?Sb,N?and?C,S?co-doped SnO₂ were prepared and their photoelectric performance were tested.The main contents of this paper are as follows:1.In the first part,donor-acceptor pair Sb and N was selected to modify SnO₂.The geometric configuration and electronic structure of pure and?Sb,N?co-doped SnO₂ were studied by first-principle calculation.The results show that the band gap of SnO₂ is reduced 0.865 eV by new energy levels of Sb and N at the bottom of conduction band and the top of valence band respectively.In addition,the charge compensation effect between Sb and N enhances the carrier separation rate of SnO₂.Based on the first-principles calculation results,pure and different ratios of?Sb,N?co-doped SnO₂ electrodes were prepared by hydrothermal method and characterized.The experimental results show that the photoelectric performance of SnO₂ is significantly improved by?Sb,N?co-doping,of which 5%?Sb,N?co-doped SnO₂ has the best photoelectric performance.The maximum photocurrent?9?A/cm²?and the minimum electrochemical impedance were obtained in the 5%co-doped samples.The theoretical calculation and experimental results indicate that the photocatalytic performance of SnO₂ is improved by?Sb,N?co-doping and donor-acceptor pair doping method can be used to prepare high active SnO₂-based photoelectric materials.2.In the second part,double-hole-assisited coupling doping of carbon and sulfur in SnO₂ was explored.The geometric configuration and electronic structure of pure and?C,S?co-doped SnO₂ were studied by first-principles calculation.The results prove that the interaction between carbon and sulfur atoms is caused by lattice distortion.C and S introduce new energy levels at the top of the valence band,which reduces the band gap by 0.622 eV.In addition,the full energy levels can inhibit the formation of charged defects,thus improving the photoelectric performance of SnO₂.In order to explain the interaction mechanism between dopant C and S,double-hole-assisited coupling mechanism of dopants in SnO₂ was also investigated.Meanwhile,based on the theoretical calculation results,pure and different ratios of?C,S?co-doped SnO₂were prepared,and their photoelectric performance was tested.The experimental results show that the photoelectric performance of SnO₂ is significantly improved by?C,S?co-doping,of which 5%?C,S?co-doped SnO₂has the best photoelectric performance.In this ratio,the maximum photocurrent value?6.8?A/cm²?and the minimum electrochemical impedance are obtained.The results show that?C,S?co-doping can prepare high active SnO₂-based photoelectric materials,which also provides a new idea for the modification of other similar semiconductor materials.