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

Abstract Modification of TiO2 with copper oxides clusters (CuOx-TiO2) induces visible-light absorption and enhances its activity. In this work, we investigated the CuOx-anatase and CuOx-rutile for the photocatalytic oxidation of gaseous NH3 under visible light. In contrast with the widely reported results that CuOx-anatase displays higher performance than CuOx-rutile in photocatalytic oxidation or reduction, we surprisingly observed that CuOx-rutile is able to oxidize NH3 efficiently under visible light irradiation, while CuOx-anatase shows no activity. Further characterizations showed that visible-light inclines to drive the VB electrons of rutile TiO2 to CuOx at the interface between rutile TiO2 and CuOx, while it drives the electrons of CuOx to anatase TiO2 at interface between anatase TiO2 and CuOx. DFT calculations revealed that the interaction between CuOx and TiO2 is markedly different in CuOx-anatase and CuOx-rutile, which induces the differences in the electronic distribution of interfacial Cu, O and Ti atoms, resulting in the distinct direction of charge transfer.