We report the synthesis of nanostructured nickel oxide (NiO) films, and their implementation as photocathodes in photoelectrochemical (PEC) cells for hydrogen generation by water splitting. NiO nanograins were prepared by electrodeposition of nickel from complexing glycinate solution at different pH from 2 to 13, followed by annealing at 400 degrees C. The characterization of NiO films was carried out by XRD, SEM, UV-vis, PL and electrochemical techniques. XRD study showed that NiO with cubic structure was obtained for all films. SEM micrographs showed a spherical-granular structure for NiO films with a grain size between 400 and 125 nm. The measurements carried out on PEC cell with NiO as photocathodes, under simulated solar irradiation, demonstrated a significant increase of cathodic photocurrent as the pH of electrodeposition solution was increased. Analysis of Mott-Schottky plots for each NiO film showed a remarkable increment of the charge carrier density as the grain size was decreasing. (C) 2016 Elsevier B.V. All rights reserved.