Photocatalytic mechanism of TiO2–CeO2 films prepared by magnetron sputtering under UV and visible light

TiO2–CeO2 films were fabricated by r.f. reactive magnetron sputtering, and pure TiO2 and CeO2 films were also prepared for comparison. The Raman spectra, TEM, XPS, UV–visible and PL spectra were used to characterize the film structure and composition. It is found that the uniform TiO2–CeO2 films consist of TiO2 and CeO2 phases connected by CeO1.62TiO2 phase. The photocatalytic activity under UV and visible irradiation were evaluated by the degradation of methylene blue. The result under UV illumination shows that the TiO2–CeO2 films have better activity than pure TiO2 films, furthermore, the TiO2–CeO2 film is a kind of photocatalyst responded to the visible light. The electron transferring between the TiO2 and CeO2 networks via Ti–O–Ce structure units plays a great role in the photocatalysis. The visible light absorption by the CeO1.62TiO2 phase is the original cause of visible light responded photocatalysis. The holes drifting from CeO1.62TiO2 to TiO2 under inner electric field force can inject photoinduced holes into TiO2 and endow the TiO2–CeO2 composite films with photocatalysis.