In the present study, CuO/gC(3)N(4)/Bi2O3 composite is constructed as a ternary visible light active photocatalyst. Since CuO plays a critical role in enhancing the photocatalytic activity of the formed composite, its structural properties are particularly studied using synchrotron X-ray absorption spectroscopy (XAS), including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). XANES confirms the presence of Cu species with +2 oxidation state in the form of CuO. EXAFS furthermore confirms that each Cu cation is coordinated to four O anions in an approximately square planar configuration. The length of the Cu-O coordination is estimated to be 1.92 angstrom, slightly shorter than that of bulk CuO (1.95 angstrom). The CuO/gC(3)N(4)/Bi(2)O(3 )composite exhibits highly enhanced photocatalytic activity in the 2,4-dichlorophenol decomposition under visible light. The enhanced photocatalytic activity is due to the increased population of electrons and the successful consumption of the photoproduced electrons by the dissolved oxygen through the one-electron transfer reaction. (C) 2018 Elsevier Inc. All rights reserved.