Here we demonstrate the enhanced photoelectrochemical (PEC) performance and photocatalytic activity towards water oxidation of n-type SrTiO3 (STO) nanocubes coupled with p-type NiO nanoparticles (denoted as p-NiO@n-STO nanoparticle@nanocube), fabricated by calcining Ni(NO3)(2)-loaded STO nano cubes. High resolution transmission electron microscope studies show that intimate p-n junctions are formed between n-type STO and p-type NiO interfaces. As a p-n junction photoanode, the p-NiO@n-STO nanoparticle@nanocube nanostructures exhibit the enhanced PEC activity and photocatalytic water oxidation. The photocurrent density of the p-NiO@n-STO nanostructure electrode reaches 3.5 A cm(-2), which is 7 times higher than that (0.5 A cm(-2)) for pure STO nanocube electrode at 0 V versus Ag/AgCl. The p-NiO@n-STO nanoparticle@nanocube nanostructures also exhibit pronounced photoresponse to generate O-2. The O-2 generation is about 100 mu mol after irradiation 3 h with a 300-W Xenon lamp, which is about 1.7 times higher than that (60 mol) of pure STO nanocubes. The intimate p-n junctions between p-NiO and n-STO interfaces accelerate holes migration from valence band of n-STO to that of p-NiO and reduction of the recombination of electron-hole pairs by the internal electrostatic field in the interface, which are believed to be the main reasons for enhanced PEC response and water-splitting performance of the as-prepared p-NiO@n-STO nanoparticle@nanocube nanostructures. The present work demonstrates that the p-n junction p-NiO@n-STO heterostructures have great potential applications in the field of photoelectrical devices and photocatalysis for water splitting. (C) 2016 Elsevier B.V. All rights reserved.