Visible-Light-Active Semiconductor Heterojunctions for Enhanced Photocatalytic Activity

摘要

A clean and sustainable energy source is a basic requirement for addressing the current increase in global energy demand and environmental issues. Because of its potential for solving current energy and environmental problems, semiconductor-based photocatalysis has received tremendous attention in the last few decades. A significant number of studies have been recently reported on the development of new photocatalytic materials, modification of existing materials to enhance light harvesting, and increasing the number of active sites in order to buttress photocatalytic activity. In a semiconductor photocatalytic system, photo--induced electron-hole pairs are produced when a photocatalyst is illuminated by light with frequencies larger than that of its band gap (h&ngr; ≥ Eg). The resulting photo-excited charge carriers can either recombine with no activity or migrate to the surface of the semiconductor without recombination, where they can be involved in redox processes. The photocatalytic efficiency depends on the number of charge carriers taking part in the redox reactions and on the lifetime of the electron-hole pairs generated by the photoexcitation. High recombination of photo excited charge carriers and limited efficiency under the visible light are the two limiting factors in the development of efficient semiconductor-based photocatalysts.;Many strategies have been developed in semiconductor photocatalysis to overcome these drawbacks. Amongst these strategies, heterojunction formation by using two or more semiconductor catalysts is a promising approach to achieve enhanced visible light induced photocatalysis by reducing the photogenerated electron-hole pair recombination. In this study, several visible light active heterojunctions containing two different semiconductors with suitable band gaps and band positions were fabricated, and their photocatalytic activity was tested for hydrogen production from water reduction or environmental remediation.