Distinct photocatalytic charges separation pathway on CuOx modified rutile and anatase TiO2 under visible light

Modification of TiO 2 with copper oxides clusters (CuO x -TiO 2 ) induces visible-light absorption and enhances its activity. In this work, we investigated the CuO x -anatase and CuO x -rutile for the photocatalytic oxidation of gaseous NH 3 under visible light. In contrast with the widely reported results that CuO x -anatase displays higher performance than CuO x -rutile in photocatalytic oxidation or reduction, we surprisingly observed that CuO x -rutile is able to oxidize NH 3 efficiently under visible light irradiation, while CuO x -anatase shows no activity. Further characterizations showed that visible-light inclines to drive the VB electrons of rutile TiO 2 to CuO x at the interface between rutile TiO 2 and CuO x , while it drives the electrons of CuO x to anatase TiO 2 at interface between anatase TiO 2 and CuO x . DFT calculations revealed that the interaction between CuO x and TiO 2 is markedly different in CuO x -anatase and CuO x -rutile, which induces the differences in the electronic distribution of interfacial Cu, O and Ti atoms, resulting in the distinct direction of charge transfer.