Cu2O nanoparticles (NPs) were directly formed on g-C3N4 via a one-pot in-situ reduction method. The physical and photophysical properties of these Cu2O NPs modified g-C3N4 photocatalysts were characterized to investigate the effects of Cu2O NPs on the photocatalytic activities of g-C3N4. Close contact was formed between Cu2O and g-C3N4 and the Cu2O NPs were well dispersed on g-C3N4. The visible light photocatalytic hydrogen production activity over g-C3N4 was enhanced by more than 70% with Cu2O NPs modification. It is revealed that the efficient visible light absorption and Type II band alignment induced charge separation by Cu2O NPs modification should be the key factors for improved photocatalytic performance. (c) 2014 Elsevier B.V. All rights reserved.