Preparation And Photocatalytic Performance Of Strontium Titanate-based Semiconductor Heterojunction

With the rapid growth of the world’s population and the continuous advancement of industrialization,the increasingly serious energy crisis and environmental problems have aroused widespread concern of the human society.Therefore,the development of green new energy is imminent.Hydrogen Energy,because of its combustion pollution-free,renewable,environmentally friendly and is considered as a new energy with great potential.In many hydrogen production methods,the use of semiconductor photocatalytic decomposition of water to hydrogen,with its pollution-free,low-cost and become the current research hotspot.Perovskite-based photocatalysts,especially strontium titanate-based photocatalysts,have attracted much attention due to their excellent energy level structure,unique photophysical and electrochemical properties.Strontium titanate is an n-type semiconductor,which is non-toxic,low cost,excellent photochemical stability and large energy span,so it is very suitable for photocatalytic hydrogen production,at the same time,the photocarrier recombination rate of the monomer material is high,so the photocatalytic hydrogen production is difficult to meet the actual needs.In order to solve the above problems,an effective improvement method is proposed and the photocatalytic performance of SrTiO₃-based semiconductors is improved successfully.The specific work is as follows:（1）Firstly,SrTiO₃ nanoparticles were prepared by solvothermal method,and then the Cd S/SrTiO₃ heterojunction was prepared by oil bath method,the effect of the loading of Cd S nanoparticles on the performance of photocatalytic hydrogen production was studied.The results show that the loading of Cd S nanoparticles can enhance the response range of SrTiO₃ nanoparticles to visible light,and the formation of heterojunction can promote the photocarrier separation,prolong the lifetime of photocarriers,and finally enhance the photocatalytic performance.After tested for photocatalytic hydrogen production,the optimum hydrogen yield of Cd S/SrTiO₃heterojunction was 272.86μmol/g?h,which was 4.5 times of pure SrTiO₃.（2）On the basis of above research,p-type Co₃O₄ films were deposited on the surface of Cd S/SrTiO₃ core-shell heterojunction.The results show that the hydrogen production performance of the as-prepared ternary Co₃O₄/Cd S/SrTiO₃ core-shell pn junction exhibits an obvious photocatalytic enhancement of～15-fold compared to single SrTiO₃ nanospheres.This improvement can be mainly ascribed to the narrow band gaps of Cd S and Co₃O₄ increasing the visible light response,and the double pn junctions quickly diffusing photogenerated charge carriers into water.Additionally,the ultrathin Co₃O₄ lamellas can shorten the photoelectron transport path.Therefore,the performance of photocatalytic hydrogen production is improved effectively.（3）In order to optimize the practical application of SrTiO₃-based photocatalyst,Mn O_x/Cd S/Ti³⁺-SrTiO₃ core-shell heterojunction is fabricated via a continuous solvothermal-annealing-chemical-photodeposition method,and achieve a decent overall water splitting performance of about～176.07（H₂）/86.03（O₂）μmol/g?h,which can be mainly ascribed to the well matched HER/OER process and formation of heterojunction.There,the Ti³⁺/O_v with new potential can increase the solar efficiency,accelerate the photo-generated electrons diffusion and reduced water splitting activation barrier,the Mn O_x with mixed chemical valance Mn³⁺/Mn⁴⁺ions can activate the hole-related species and promote the H₂O₂ decomposition,and the formation of core-shell Cd S/Ti³⁺-SrTiO₃ heterojunction can improve the charge carrier separation/transport.Additionally,the core-shell structure can inhibit the photocorrosion to maintain good photocatalytic stability.