Study On Modification Of Anatase TiO₂ Microspheres Composed Of Porous Single Crystals

TiO₂ has attracted much attention due to the good chemical stability,high activity,low cost,easy availability and non-toxicity.It has been considered as the one of the most important photocatalytic materials with the promising potential in practical applications.However,the photo response is basically limited in the range of ultraviolet light owing to the wide band gap of TiO₂ with the low solar utilization.Simultaneously,the high recombination rate of photo-generated electrons and holes suppress the photocatalytic activity of TiO₂.Therefore,the modification of TiO₂ photocatalyst as an important method for enhancing photocatalytic activity can improve the visible light absorption and restrain the recombination of electrons and holes.In this paper,the different modification methods of TiO₂ photocatalyst were studied including doping,porous treatment,noble metal deposition and surface disorder.Nonmetal element N doping can narrow the band gap by forming the mid-state in the band gap of TiO₂ resulting in the increasing visible light absorption.The surface areas of crystals are greatly increased through porous treatment which provides plenty active sites and shortens the transmission distance of photo-generated electrons.The separation efficiency of photo-generated electrons and holes can be improved by noble metal deposition on the surfaces of crystals to enhance the photocatalytic activity.The surface disorder forming disorder layers can enhance the visible light absorption.The effects of different modification on the photocatalytic performance of TiO₂ were also studied in this work and the as-prepared samples were characterized in detail by XRD,SEM,XPS,UV-Vis,etc.The main work and results are listed as follows:1.The micron-size anatase TiO₂ single crystals with different N doping amount were synthesized by liquid doping using chemical recovery solution as raw materials,in which the supernatant Ti N can be utilized as N source,the supernatant TiO₂ as main Ti source and the HF as the morphology control agent.The proportion of the facets of the as-synthesized crystals with active {001} and {110} facets changed with the increase of doping amount.The photocatalytic activity was examined through the degradation of methylene blue?MB?and phenol solution under visible light irradiation and the optimal N doping amount was determined in the research range.Simultaneously,this work laid a foundation for the following modification research of porous anatase crystals.2.The anatase TiO₂ microspheres composed of porous single crystals with in-situ tunable N doping were prepared by doping using liquid N source.The morphology,composition and optical response of the samples were characterized in detail using XRD,SEM,UV-Vis,PL and other measurements.Compared with the bulk crystals or undoped porous microspheres,N-doped porous microspheres exhibited higher photocatalytic performance.With the increase of N doping amount,the photocatalytic activity gradually enhanced.This is due to the synergistic effect of porous structure and N doping.3.Noble metal Ag loaded on the surfaces of porous TiO₂ crystals was performed by chemical reduction method and the samples with different Ag-loaded amount were characterized.The photocatalytic activity of all samples was investigated by the degradation of MB under UV light irradiation.At last,the optimal Ag-loaded amount was ascertained.The conclusion can be drawn: appropriate Ag-loaded amount can improve the photocatalytic performance of materials through increasing the visible light absorption and promoting the separation of carriers.4.The TiO₂ anatase microspheres composed of porous single crystals were synthesized using?NH4?2Ti F6 as precursor and the porous samples were treated with surface hydrogenation.Then,all samples were characterized and their photocatalytic activity was evaluated by the degradation of methyl orange?MO?.According to the measurements,the samples after hydrogenation displayed the best photocatalytic performance.This paper provides a new thinking and novel method for improving the photocatalytic performance of TiO₂ crystals as well as further practical applications by the research on modification of TiO₂ microspheres.