The hybrid catalyst of g-C3N4-PWO has been prepared through the calcination of the g-C3N4 precursor of dicyandiamide and the polyoxometalates (POMs) precursor of (NH4)(3)PW12O40 (NH4-PW12). The hybrid catalyst of g-C3N4-PWO with well-defined and stable structure exhibits efficient catalytic performance for photocatalytic H2O2 production in the absence of organic electron donor under visible light. The value of electron transfer during the oxygen reduction reaction (ORR) process obtained from the Koutecky-Levich plot for g-C3N4-PWO (n = 1.73) is higher than that for g-C3N4 (n = 1.29), suggesting that the PWO incorporated into g-C3N4 framework can promote the electrons generation. The p-benzoquinone (PBQ) scavenger experiments, the electron spin resonance (ESR) signal and quantitative experiment of superoxide radicals (O-center dot(2)-) results reveal that the negative shifts of the conduction band (CB) level from g-C3N4 to g-C3N4-PWO can enhance the single-electron reduction of O-2 to O-center dot(2)- and further promote the sequential two-step single-electron O-2 reduction reaction to H2O2. (C) 2018 Published by Elsevier Inc.