Proparation And Photocatalytic Property Of Visible-light-induced Nanosized Cu₂o-tio₂

As one of the most famous and widely used semiconductors, TiO₂ owns certain outstanding advantages, such as non-toxicity, stability and low-cost, etc. However, its efficiency of utilizing solar energy is heavily limited due to the restricted absorbance of visible light. In this thesis, a narrower band gap semiconductor Cu₂O was used to couple with TiO₂ to form Cu₂O/TiO₂ heterostructure, which exhibited highly enhanced photocatalytic efficiency under visible light irradiation. TiO₂/Cu₂O photocatalysts,Cu₂O-TNTs photocatalysts,Ag/TNTs and Cu₂O-Ag/TNTs photocatalysts were characterized by morphology analysis, specific surface area analysis, absorption spectra and photocatalytic activity in degradation of methyl orange under visible light.Densities of states, band structure, absorption spectrum of TiO₂/Cu₂O were investigated by first principles calculation in this dissertation. The results indicate that band gap of the photocatalyst was narrowed after coupling with Cu₂O. The main reason causing narrowed band gap was a new band gap forming in the TiO₂ band gap.TiO₂/Cu₂O composite photocatalysts with different molar ratio of Cu²⁺/Ti⁴⁺ were prepared by a simple"soak-deoxidize"method, and were characterized by X-ray diffraction, scanning electron microscopy and UV–vis diffuse reflection spectra. The photocatalytic activity of TiO₂/Cu₂O composites was evaluated by degradation of an azo dye, methyl orange (MO) in water under visible light irradiation. The results showed that the photocatalytic activity of TiO₂/Cu₂O composite was obviously improved comparing with that of TiO₂ (P25) and pure Cu₂O. The TiO₂/Cu₂O composite (made by Cu²⁺/Ti⁴⁺ molar ratio of 1:2) showed the best photocatalytic efficiency. The degradation ratio of methyl orange was 86% irradiating under visible-light for 120 min.Titania nanotubes(TNTs) with a diameter of 10nm around, length ranging from dozens to hundreds of nanometers, wall thickness of 2 3nm around can be prepared by hydrothermal method , and own hollow pipe and an open-ending morphology. The specific surface area of nanotubes was 240.60 m²Â·g^-1. The absorption of TNTs located at 380nm, resulting in no methyl orange being degraded under visible irradiation.Cu₂O/TNTs composite photocatalysts were also prepared by the simple"soak-deoxidize"method. 5-10nm Cu₂O particles were deposited on the surface of TNTs. The influence of preparation condition such as stirring time, Ti and Cu elements molar ratio and the precursor were investigated. When the stirring time, of 6h, Ti: Cu elements molar ratio of 2:1 and TNTs calcinated at 400℃as precursor, the samples have specific surface area of 203.45 m²Â·g^-1and light absorption range of 260-520nm, showing significantly improved photocatalytic activity compared with TNTs and P25.Ag/TNTs and Cu₂O-Ag/TNTs composite photocatalysts were prepared by photodeposition method and simple"soak-deoxidize"method. The degradation ratio of methyl orange using Cu₂O-Ag/TNTs was 25% irradiating under visible-light for 180 min. It showed higher visible catalytic activity than TNTs and P25. The improved photocatalytic activity of nano heterojunction system can be attributed to the use of visible light, photoinduced charges increased, and enhanced separation/migration process.