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In this work, efficient NiO nanoparticles/TiO 2 nanorods p-n heterojunction structure photocatalyst is constructed by reasonable design of two-step calcination technology and examined for hydrogen production activity from methanol-water mixture. In the NiO/TiO 2 heterojunction structure small NiO nanoparticles are evenly distributed on the surface of TiO 2 and tightly connected together with TiO 2 , as it was determined by microscope characterization techniques, which conducive to the interface transport of photogenerated carriers. The novelty of this paper is the detailed characterization of NiO/TiO 2 photocatalysts by electrochemical technics as Transient photocurrent response, Mott-Schottky plots, linear sweep voltammograms and Electrochemical impedance spectroscopy and their correlation with photoactivity. The rationally designed NiO/TiO 2 p-n heterojunction promotes the transfer of photogenerated electrons and inhibits carrier recombination. The highest hydrogen production was exhibited in the presence of the 2-NiO/TiO 2 composite during 3 h of UV irradiation (701 μmol/g cat.), which exceeded the activity of pure TiO 2 by more than 1.3 times. The loss of photocatalytic hydrogen yield is negligible after repeating cycle reactions. Finally, a possible p-n heterojunction photocatalytic reduction mechanism has been discussed and apparent quantum yield was calculated. [Display omitted] • NiO nanoparticles/TiO 2 nanorods p-n heterojunction photocatalyst was constructed. • NiO/TiO 2 exhibited higher photoactivity for H 2 production in comparison with TiO 2. • Correlation of photoelectrochemical measurements with photoactivity of NiO/TiO 2. • NiO/TiO 2 p-n heterojunction inhibits carrier recombination. • Apparent Quantum Yields were calculated. [ABSTRACT FROM AUTHOR]