Towards sustainable energy. Photocatalysis of Cr-doped TiO2: 4. Electrochemical coupling

The present chain of five papers considers the concept of solar-to-chemical energy conversion using TiO 2 -based semiconductors. The series reports the effect of chromium on the key performance-related properties of polycrystalline TiO 2 (rutile), including electronic structure, photocatalytic activity, intrinsic defect disorder, electrochemical coupling and surface versus bulk properties. This work reports the effect of photoelectrochemical coupling of both pure and Cr-doped TiO 2 on photocatalytic partial water oxidation. The couples are annealed in oxidising and reducing conditions, at p (O 2 ) = 10 5 Pa and p (O 2 ) = 10 −10 Pa, respectively. The performance of the coupled system may be enhanced, or retarded, by the electrical potential barrier that is formed between the couple components as a result of the difference in Fermi levels. In this work, we show that the potential barrier results in the effect of synergy when the charge transport within the couple components is high enough. This is the case for the couples annealed in reducing conditions.