Efficient Separation of Photoexcited Charge at Interface between Pure CeO and Y-Doped CeO with Heterogonous Doping Structure for Photocatalytic Overall Water Splitting.

Enhancement of photoexcited charge separation in semiconductor photocatalysts is one of the important subjects to improve the efficiency of energy conversion for photocatalytic overall water splitting into H and O. In this study, we report an efficient separation of photoexcited charge at the interface between non-doped pure CeO and Y-doped CeO phases on particle surfaces with heterogeneous doping structure. Neither non-doped pure CeO and homogeneously Y-doped CeO gave activities for photocatalytic H and O production under ultraviolet light irradiation, meaning that both single phases showed little activity. On the other hand, Y-heterogeneously doped CeO of which the surface was composed of non-doped pure CeO, and Y-doped CeO phases exhibited remarkable photocatalytic activities, indicating that the interfacial heterostructure between non-doped pure CeO and Y-doped CeO phases plays an important role for the activation process. The role of the interface between two different phases for activated expression was investigated by selective photo-reduction and oxidation deposition techniques of metal ion, resulting that the interface between two phases become an efficient separation site of photoexcited charge. Electronic band structures of both phases were investigated by the spectroscopic method, and then a mechanism of charge separation is discussed.