Bifunctional photocatalysis of TiO2/Cu2O composite under visible light: Ti3+ in organic pollutant degradation and water splitting

Photocatalytic experiment results under visible light demonstrate that both TiO2 and Cu2O have low activity for brilliant red X-3B degradation and neither can produce H-2 from water splitting. In comparison, TiO2/Cu2O composite can do the both efficiently. Further investigation shows that the formation of Ti3+ under visible light has great contribution. The mechanism of photocatalytic reaction is proposed based on energy band theory and experimental results. The photogenerated electrons from Cu2O were captured by Ti4+ ions in TiO2 and Ti4+ ions were further reduced to Ti3+ ions. Thus, the photogenerated electrons were stored in Ti3+ ions as the form of energy. These electrons trapped in Ti3+ can be released if a suitable electron acceptor is present. So, the electrons can be transferred to the interface between the composite and solution to participate in photocatalytic reaction. XPS spectra of TiO2/Cu2O composite before and after visible light irradiation were carried out and provided evidence for the presence of Ti3+. The image of high-resolution transmission electron microscopy demonstrates that TiO2 combines with Cu2O tightly. So, the photogenerated electrons can be transferred from Cu2O to TiO2. (C) 2011 Elsevier Ltd. All rights reserved.