| The solar energy utilization is a promising method to solve the problem of energy crisis. In the current methods of solar energy utilization, solar photocatalytic water splitting is one of the most feasible method, which can convert the solar energy to chemical energy. In the field of environmental and energy, using the solar photocatalytic water splitting for hydrogen production has the broad application prospects. In the past few decades, people have putted a large amount of energy in this field, and made many great achievements. Many semiconductor material with photocatalytic properties such as TiO2, CdS, ZnS, NaTaO3 and KNbO3 and so on have be found. But, these materials have two serious defects in the field of photocatalysis:firstly, the bandwidth of most of the high active semiconductor materials is very wide, only absorbing the high-energy ultraviolet light. Unfortunately, the ultraviolet-light part accounts for only 5.0% in the sunlight, which inevitably makes the solar energy utilization rate of these semiconductor extremely low. secondly, the recombination rate of electron-hole is very high, leading to the low semiconductor quantum efficiency. Therefore, in order to realize the practical application of solar photocatalytic water splitting for hydrogen production, solving this two problems has been the focus of all the scientists.In recent years, our group has focused on the using up-conversion luminescent material to improve the photocatalytic efficiency. This is mainly because the up-conversion luminescent material can convert the low energy visible light into high-energy ultraviolet light, which can provide more ultraviolet for semiconductor photocatalyst. In addition, due to the cocatalyst promoting the electron-hole pairs separation so, we also introduced some cheap material as cocatalyst to replace traditional precious metal cocatalyst to improve the photocatalytic efficiency of the semiconductor.In this thesis, the semiconductor Ta2O5 as photocatalyst, we study in detail some influence factors on up-conversion luminescent agent-Ta2O5-cocatalyst system. In the paper, firstly, the Ta205 catalyst was synthesized by sol-gel method. Secondly, the up-conversion luminescent agent Tm3+,Yb3+:NaYF4 was synthesized by solvothermal method and the Er3+:YAlO3 was synthesized by sol-gel method. Thirdly, the cocatalyst system, reduced graphene oxide (RGO)-MoSe2 was preparaed by the method of hydrothermal method. Lastly, the infrared-light photocatalytic activity Tm3+,Yb3+:NaYF4/MoS2-Ta2O5 and visible-light photocatalytic activity Er3+:YAlO3na2O5/MoSe2-RGO and Er3+:YAlO3/Ta2O5-CaIn2S4/MoSe2-RGO compounds were prepared by the method of particle mixing and impregnated. Throught the XRD, SEM, TEM, UV-vis spectra, PL, EDX and XPS respectively characterized the preparation of luminescent materials and photocatalyst. In addition, we also studied the influence of mass ratio of up-conversion luminescent agent and Ta2O5, heat treatment temperature, heat treatment time and initial acidity of the solution on photocatalytic system.Through the research of up-conversion luminescent agent-Ta2O5-cocatalyst system, we could find that compositong the up-conversion luminescent material with traditional photocatalyst and loading the appropriate cocatalyst to prepara the new photocatalyst could not only improve the utilization efficiency of sunlight but also provide a new way for future large-scale solar photocatalytic water splitting for hydrogen production. |
PDF Full Text Request