Construction of titania–ceria nanostructured composites with tailored heterojunction for photocurrent enhancement

Titania–ceria (TiO2–CeO2) nanostructured composites based on the design of coating the surfaces of anodized TiO2 nanotube arrays with small band gap CeO2 nanoparticles have been constructed and characterized to demonstrate the effectiveness of the TiO2–CeO2 semiconductor heterojunction in enhancing the photocurrent response of TiO2-based photoelectrodes. The TiO2–CeO2 heterojunction was confirmed to possess conduction and valence band offsets (0.81 and 1.59 eV, respectively) which promote the separation of photoinduced electron–hole pairs. The photocurrent densities of the TiO2–CeO2 composites prepared with low annealing temperatures were about 25–40% larger than that of the anatase TiO2 nanotube arrays. When the nanoparticle-on-nanotube architecture of the TiO2–CeO2 heterostructure was maintained under specific processing conditions, the benefits of having a high specific surface area, a small band gap component capable of absorbing visible light, and a favorable heterojunction were achieved together for photocurrent enhancement.