Preparation Of Indium-based Semiconductor Materials And Their Photocatalytic Properties

With the application of antibiotics in disease treatment and livestock breeding,their metabolites enter the water environment and accumulate in the water as they are not easily degraded,causing a serious threat to human health and destroying the ecosystem.Photocatalytic technology has the advantages of being able to use clean and renewable solar energy,safe and efficient without secondary pollution,and complete mineralization of pollution,which is widely used in the field of degrading organic pollutants.The development of environmentally friendly,stable and efficient visible light-driven photocatalysts is its primary concern.In₂O₃has disadvantages such as low absorption of visible light and fast rate of photogenerated charge complexation.Metal organic frameworks（MOFs）have the advantages of large specific surface area,regular voids and abundant active sites,which can be used as precursors and modified to enhance the photocatalytic performance of In₂O₃.In this paper,MIL-68（In）-NH₂was used as a precursor to improve the photocatalytic activity of In₂O₃by elemental doping,composite semiconductor materials to construct heterojunctions and derivatization.The crystalline phase structure,morphological structure,surface chemistry and optoelectronic properties were analyzed by characterization techniques.The degradation rate of tetracycline hydrochloride（TCH）in water was used as the criterion for the photocatalytic performance.The reasons for their enhanced photocatalytic performance and possible degradation mechanisms were investigated to provide an effective modification method for improving the photocatalytic performance of metal oxides.The main elements are:1.Tubular carbon-covered cobalt-doped bi-crystalline phase In₂O₃（denoted as CoInO-x）was synthesized by one-step calcination of the metal-organic framework cobalt-doped MIL-68（In）-NH₂precursor.CoInO-x photocatalytic activity was investigated by degradation of TCH.Under visible light irradiation,TCH removal by CoInO-500 was 90.1%obtained by calcination at 500℃,significantly higher than that of In2O3.In₂O₃.CoInO-500 had 11.02 times the reaction rate constant of In₂O₃and maintained a good photocatalytic performance after 4 cycles.The experiment investigated the effects of CoInO-500 dosing,pH and inorganic anions on the photocatalytic performance.Explanation of possible mechanisms of photocatalytic degradation through reactive radical trapping experiments and Mott-Schottky tests.Enhanced photocatalytic performance is mostly attributed to the cobalt doping creating impurity energy levels and narrowing the forbidden bandwidth of In₂O₃,improving the response to visible light and suppressing photogenerated charge complexes.Carbon covering can serve as a bridge for charge transport,accelerating the rapid transport of photogenerated charges.2.In₂O₃/Bi₅O₇I heterojunctions（IB-y,y is the mass ratio of In₂O₃/Bi₅O₇I）were prepared by calcination of a mixture of MIL-68（In）-NH₂/BiOI.Bi₅O₇I nanosheets were dispersed on the surface of hollow tubular In₂O₃.Within 60min of visible light irradiation,the degradation rate of IB-12 for TCH was90.1%,which was 20.7 and 24.2 times higher than that of In₂O₃and Bi₅O₇I,respectively.IB-12 photocatalytic activity was increased because In₂O₃and Bi₅O₇I constructed heterojunctions,which inhibited the compounding of photogenerated charges,narrowed the band gap and broadened the response to light.The influences of IB-12 dosing,pH and co-existing ions on the photocatalytic performance were investigated.IB-12 was able to maintain a high catalytic activity after four cycling experiments,indicating its good cycling stability.Possible photocatalytic degradation mechanisms were deduced by capturing reactive radicals experiments,electron paramagnetic resonance（EPR）characterization and photoelectrochemical tests.