Synthesis Of Semiconductor Photocatalysts With Visible-light Response And Their Photocatalytic Performance

As an effective solution of solving the problems of resource crises and environmental pollution, semiconductor photocatalysis has attracted extensive attention in recent years. Among those studies, the comprehensive utilization of solar energy and the increase of quantum efficiency are two main challenges for the design of new types of semiconductor photo catalysts. As a traditional and widely used photocatalyst, TiO2 can only use UV energy because of its wide band-gap; therefore, the synthesis of TiO2-based photocatalysts with visible light activity is critical for the application of TiO2. It has been demonstrated recently that silver phosphate shows strong visible light response ability. The apparent quantum yield is greater than 80%(ca.480 nm) in Ag3PO4 suspension. However, the photocatalytic efficiency and stability of Ag3PO4 need to be greatly enhanced. Hence, in this dissertation, the enhanced visible-light-driven photocatalysts with a wide photo-response range and quick separation of photo-generated carries (electrons and holes) have been developed by two-step treatment of TiO2 and surfactant-assisted co-precipitation of Ag3PO4. The thesis contains two parts:1. The fluorination mesoporous TiO2 (F-TiO2) was prepared by hydrofluoric acid (HF) hydrothermal etching of commercial P25. The as-prepared F-TiO2 was subjected to subsequent treatment with H2 Dielectric Barrier Discharge (DBD) plasma; finally, the mesoprous F-TiO2-x with abundant oxygen vacancies was obtained. F-TiO2-x possesses a unique crystalline core/amorphous shell structure (TiO2@TiO2-x).F-TiO2 shows an enhanced visible-light response under visible-light irradiation compared with P25. Due to the core/shell structure and more oxygen vacancies, F-TiO2-x exhibits wide range response and enhanced visible light photocatalytic activity compared with F-TiO2. The abundant oxygen vacancies (Ti3+) and F in F-TiO2 or F-TiO2-x lead to new localized level. Therefore, the photocatalyst has a narrowed band gap and improved visible-light absorption, as a result, high photocatalytic activity is achieved.2. During the co-precipitation of Ag+ and PO43-, sodium dodecyl sulfate (SDS) was introduced in the aqueous system to prepare SDS-Ag3PO4 hybrid with more photocatalytic cites. The degradation rate of methylene blue (MB) was almost three times faster in SDS-Ag3PO4 suspension under visible-light illumination than that of Ag3PO4 obtained by the co-precipitation in the presence of SDS. The excellent photocatalytic activity of the SDS-Ag3PO4 hybrid was attributed to its enhanced adsorption of dyes, a low recombination rate of photo-generated carriers and an improved optical absorption.