In this work, the oxygen-doped C3N4@TiO2 (O-C3N4@TiO2) composites with quasi-shell-core nanostructure were fabricated by coating a monolayer or multilayers of O-C3N4 onto the surface of TiO2 nanoparticles. Compared with the C3N4@TiO2 quasi-shell-core nanocomposite, the O-C3N4@TiO2 quasi-shell-core nanocomposite exhibits a significant promotion of the photoelectrochemical and photocatalytic performance of TiO2, owing to the interfacial chemical bonds formed between the hydroxyl residues on TiO2 surface and the oxidizing groups on O-C3N4 surface induced by oxygen doping. The experimental results of UV/Vis diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, photoluminescence spectroscopy and excited state electron attenuation spectroscopy further reveal that this interfacial chemical bonds formed between O-C3N4 and TiO2 can become effective transfer channels for the photogenerated electrons, help to capture the electrons from the valence band of O-C3N4 and rapidly quench the photogenerated holes of TiO2, thereby effectively reducing the recombination efficiency of the photogenerated electrons and holes. (C) 2014 Elsevier Ltd. All rights reserved.