| The global energy demand is high and industrial pollution is serious.Currently,energy crisis and environmental pollution are two major problems closely related to human production and life.Since the discovery of photocatalysis,it has gained continuous attention in the development of clean energy and degradation of organic wastewater,and SrTiO3 is a typical perovskite wide band gap metal oxide semiconductor.It has been found to have photocatalytic properties at a very early stage,but it has been difficult to develop and apply in industrial scale due to the existence of problems such as wide band gap and difficult recovery.For these problems of SrTiO3,in this study,the energy band structure and magnetic properties of SrTiO3 are modulated by doping modification method mainly through both theoretical prediction and experimental synthesis,so as to achieve the effect of improving photocatalytic efficiency.This study is mainly divided into two parts:theoretical simulation and experiment,and the main research contents and conclusions are as follows.Firstly,the performance of(P+V)co-doped SrTiO3 photocatalysts was simulated using the GGA+Ud method.The introduction of V doping will reduce the band gap to 1.16 eV,which seriously affects the photocatalytic performance of the system,while the influence of the small ionic radius and high electronegativity of P weakens the orbital hybridization between V-3d orbitals and O-2p,which makes the band gap widths of the(P+V)near-,mid-and far-configuration co-doped systems were reduced to 2.44,1.96 and 1.94 eV,respectively,which enhanced the visible light absorption ability of the system while reducing the generation of photogenerated carrier recombination centers,and finally enhanced the photocatalytic activity of the catalyst.Secondly,in order to obtain the GGA+U method that can more accurately predict the photocatalytic effect of SrTiO3 system,both O-2p and Ti-3d were treated with+U,and a reasonable set of parameters was determined by U-value testing.Then the photocatalytic performance of P co-doped with transition metals(Fe,Co,Cr)and(Al+S)co-doped SrTiO3 was predicted using this system.For the former,Fe and Co doping,while making the catalyst magnetic,also makes the system display semi-metallic properties,which greatly reduces its photocatalytic performance.Due to the high electronegativity of P and the introduction of a hole in the system,the half-metallic properties of the Fe and Co mono-doped SrTiO3 disappears and the band gap remains in a good range.In addition to the co-doping with Fe and Co,the co-doping of SrTiO3 with P and Cr also has a more suitable band gap width and higher magnetic moment,and from the magnetic moment and charge difference density plots,we predict that Cr in the codoped system with P may be in the coexistence of+3 and+6 valence states.For the latter,when the dopants Al and S are single-doped,the band gap widths are 3.11 eV and 1.13 eV,respectively.It can be seen that the Al mono-doped band gap width is too high for visible light absorption and the valence band top exceeds the Fermi energy level,which will be unfavorable for photocatalytic reactions,while the S single-doped band gap width is too low,which will affect the photocatalytic activity.And when the two are co-doped in the ratio of 1:1,the band gap of the system is maintained at the ideal state of 2.16 eV,which provides good visible light absorption performance,which is the result of the joint action of Al and S.Finally,the combination of P modulation of the valence band beyond the Fermi energy level due to metal ion doping and the partial occupation of the valence band beyond the Fermi energy level in the near future by Al doping forms a partially occupied state.Next,the photocatalytic properties of P and Al co-doped SrTiO3 were investigated from both experimental and theoretical simulations.Firstly,P,Al single-doped and(P+Al)co-doped SrTiO3 photocatalysts were synthesized by hydrothermal method.The photocatalytic performance study showed that the co-doped SrTiO3 catalyst exhibited the highest photocatalytic activity and the lowest degradation efficiency of the P mono-doped catalyst in the simulated sunlight degradation of rhodamine B experiment.It was found by SEM scanning that the addition of P impurities would cause the catalyst to indicate the formation of more irregular small particles,which would facilitate the contact between the catalyst and the reactants.The band gap width calculated by UV-vis DRS indicates that P doping increases the band gap width of SrTiO3,while P co-doping with Al decreases the band gap width of the catalyst by 0.06 eV.The co-doped system is more favorable to improve the photocatalytic performance.Then the density of states and differential charge density characterization were performed using the first nature principle,and the mechanism of the effect of charge-compensated co-doping between P and Al on reducing the band width of SrTiO3 catalyst was found.Through the above studies,the modulation of the energy band structure of strontium titanate-based photocatalysts by doping was achieved from both theoretical and experimental perspectives,and the performance of the catalysts was improved.A theoretical and experimental basis is provided for the modification of the doping of calcium titanate-based photocatalysts.Figure[41]Table[6]Reference[91]... |
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