In this study, we have found that CuOx modified alpha-Bi2O3 is an excellent photocatalytic material for the visible-light-driven degradation of various organic compounds including RhB, MO, 2,4-DCP, and gaseous IPA. A detailed study on the mechanism of the photocatalytic reaction was performed by measuring the photogenerated (OH)-O-center dot and H2O2 under visible light irradiation. The results indicate that modifying CuOx on the surface of alpha-Bi2O3 significantly promotes the separation of the photogenerated electrons and holes of alpha-Bi2O3. The important role of CuOx was further investigated by detecting the valence states change of Cu before and after the photocatalysis, using ESR and XPS. It was found that, the Cu states within the CuOx clusters are the coexistence of Cu(II) clusters, CuO and Cu. As a result, the enhancement of photocatalytic activity by CuOx modification can be attributed to a CuOx-assistant electron transfer process (CuOx-AETP), which involves in two electron excitation paths and a Cu cycle of different valence states. (C) 2014 Elsevier B.V. All rights reserved.