In this work, we fabricate a ternary nanocomposite photoelectrode consisting of TiO2 nanoparticles, polyoxometalate (P2W18) and copper quantum dots (Cu QDs) so as to create a synergistic effect of the ternary nanocomposite on photovoltaic and photoelectrocatalytic performances. Both the high electron mobility from low cost Cu QDs and the high electro-hole separation efficiency from P2W18 could evidently improve the photoelectrochemical performance of TiO2. Transient photocurrent and current-voltage curves measurements demonstrate that both the photocurrent response and power conversion efficiency of the P2W18/Cu/TiO2 film were markedly enhanced in comparison with that of the only TiO2 film and the P2W18/TiO2 film, respectively. Furthermore, the photoelectrode also exhibited significant photoelectrocatalytic activity for formic acid oxidation. The substitute of copper quantum dots for noble metals in electrode is a favorable innovation for the practical application of photoelectrochemical devices. (C) 2014 Elsevier Ltd. All rights reserved.