Study On The Preparation And Performance Of Visible/Near-infrared Light Responsive Semiconductor Photocatalysts

In the 21^st century,energy crisis and environmental pollution are the two themes concerned by all countries around the world.Semiconductor photocatalytic technology,which can effectively solve environmental pollution and energy crisis,has caused wide attention of researchers both at home and abroad.TiO₂,Fe₂O₃ and SiC semiconductor materials are the most commonly used semiconductor photocatalysts,and have been widely used in the field of sterilization,sewage treatment,air purification,water splitting,etc.However,there are many shortcomings existing in these semiconductor photocatalyst materials,such as low solar energy utilization efficiency,high photogenerated carriers'recombination rate,which largely hinder their practical application and commercialization.In this thesis,we modified TiO₂,Fe₂O₃ and SiC photocatalytic nanomaterials through defects doping,semiconductor compositing,upconversion luminescence enhancing and other methods,in order to achieve efficient and stable photocatalysts.The concrete research content is as follows:1)Oxygen vacancy doped TiO₂ film was fabricated by anodic oxidation and hydrogen annealing on TLM substrate.The study investigated the influence of oxygen vacancy on light absorption band structure of TiO₂,the visible-light driven photocatalytic activity was evaluated.The results indicated that the second oxidized nanoporous TiO₂ film has better bonding force with TLM than the first anodic oxidized film.Hydrogen annealing introduces oxygen vacancy into TiO₂,and broadens its optical absorption range.The doping amount of oxygen vacancy can be controlled by changing annealing temperature.The sample shows excellent photocatalytic performance for degrading RhB and decomposing Escherichia coli,Staphylococcus aureus under visible light irradiation.2)RGO-Fe₂O₃-MoS₂ nanocomposites were fabricated through two step hydrothermal method.The study investigated the influence of the loading amount of Fe₂O₃ and MoS₂ on the sample morphology and structure,analyzed its interface contact form and optical performance,evaluated its visible-light driven photocatalytic activity and explored the two main transfer mechanisms of photogenerated carriers.The results indicated that the 3D RGO-Fe₂O₃-MoS₂ nanocomposites possess large surface specific area,good optical absorption ability and high photogenerated carriers'separation.Therefore,the typical heterostructured RGO-Fe₂O₃-MoS₂ nanocomposites show drastically enhanced photocatalytic activity for MB degradation under visible light irradiation,and together with excellent stability.3)3C-SiC nanocrystals were prepared by chemical etching plus ultrasonic oscillation,the influence of chemical etching time on the particle size and optical absorption was explored.Secondly,two different structured Er/Tm/Yb/Y₂O₃upconversion materials were successfully fabricated through chemical coprecipitation and template methods,the effect of Er/Tm,Yb doping amounts,the precursors'concentration and the template usage on its upconversion luminescence properties was investigated.On this basis,compositing the flake-like and the chain-like Er/Tm/Yb/Y₂O₃ upconversion materials with 3C-SiC nanocrystals via dopamine,respectively.The effect of the two different structured Er/Tm/Yb/Y₂O₃ upconversion materials on the optical and photocatalytic performance of 3C-SiC nanocrystals was discussed.The results indicated that the upconversion property of chain-like Er/Tm/Yb/Y₂O₃ is much higher than the flake-like sample.The Er/Tm/Yb/Y₂O₃ can transform 980 nm near-infrared light into blue and green light which can be absorbed by 3C-SiC.Moreover,the chain-like Er/Tm/Yb/Y₂O₃-SiC composites show better photocatalytic activity than flake-like composites under 980 nm laser,and both of them display substantially improved photocatalytic activities in catalyzing decomposition of MB dyes in comparison to pure 3C-SiC NCs under Xe lamp irradiation.