Optimizationon Photocatalytic Performance Of Several Gallium Boratesand Indium Borates

Hydrogen production from water on photocatalysts is a green process to convert solar energy, and the advantage is the presumable simplicity and low cost of real applications.Nowadays, developing novel photocatalysts or modifying already reported catalysts are the main subjects in this research field.This thesis reported several gallium-containing borates and indium borate due to their d10 electron configuration.Our major project is to discover new semiconductors to expand the list of photocatalysts of water splitting, and in addition, we also intend to modify previous-reported photocatalysts to enhance their activities, during which we could obtain some general principles for improving the catalytic properties of such kind of materials. We hope it could be helpful to other researchers. We also test several gallium-containing borates by degradation of methylene blue.Besides, some preliminary exploration onseveral borates containing tantalum and niobium as new photocatalysts were carried out due to their d0 electron configuration.The main results obtained through our study are listed as below.1. MGa2B2O7(M=Ba,Sr),CaGaBO4,MBiGaB2O7(M=Ca,Cd),YGa3(BO3)4 were synthesized and characterized. the photocatalytic properties of the obtained gallium borates were investigated.The activity of these materials for degradation of methylene blue were not very high,only YGa3(BO3)4 could produce hydrogen under UV irradiation.2. The photocatalytic properties of PbGaBO4 under UV irridiation in 20% methanol solution were studied. The band gap was experimentally estimated to be 3.8 eV by the UV-vis absorption spectrum, the top of the valence band (VB) and the bottom of the conducting band (CB) are contributed by O p, Ga s and Pb p orbitals, respectively. Photocatalytic H2 evolution of PbGaBO4 synthesized by high tempreture method loaded with lwt%Pt-lwt%Ru is 4 times of parent compounds (41.9?mol/g/h and 10. 1?mol/g/h,respectively), H2 evolution rate of PbGaBO4 synthesized by gallium excitation method loaded with lwt%Pt-lwt%Ru is 4.5 times of parent compounds (36.4?mol/g/h and 8.1?mol/g/h, respectively).double cocatalysts were effective optimization method,which could promote the separation of photoinduced charge carrier, responsible for the remarkable increase in photocatalytic activity.Besides, PbGaBO4 was unstable in aqueous solution,Pt or Ru cocatalyst could prevent the compound from decomposing.3. The photocatalytic properties of YGa3(BO3)4 were studied. Photocatalytic H2 evolution of YGa3(BO3)4 is 1.5?mol/g/h under UV irradiation in 20% methanol solution,and the H2 evolution of 2%Pt-loaded samples was 4.4?mol/g/h,both were stable in photocatalytic system. Although its activity is not very high, it is possible to be improved by some methods, such as loading cocatalytic and doping various transition metal cations.4.InBO3 obtained by hydrothermal method showed fine morphology. The band gap was experimentally estimated to be 5.2 eV by the UV-vis absorption spectrum, the top of the valence band (VB) and the bottom of the conducting band (CB) are contributed by O p and Ga s orbitals, respectively, the efficiency of producing hydrogen was about 18.2?mol/h/g in methanol-water solution(20 ml methyl alcoho1,50ml water).after annealing at 350? in oxygen flowing for 5 hours,H2 evolution was improved to 29.5?mol/h/g, when NiOx 1 wt% as cocatalyst was loaded to samples by impregnation,hydrogen generated 51.6?mol/h/g,the efficiency of producing hydrogen was increased by optimization measures. Moreover, we attempt to substitute In3+ by Ga3+ from 10% to 30% in order to improve hydrogen production. However, the rate of photolysis decreased with the doping content increased.5. The photocatalytic properties of K3Nb3B2O12 and KTaB2O6 were studied, which was 11.9?mol/g/h and 1.9?mol/g/h under UV irradiation in 20% methanol solution, respectively. These materials have great potential applications, which provide some suggestions for borates containing tantalum and niobium in photocatalyst fields, and have guiding significance for the following experiments.