Potentiostatic electrodeposition of nanostructured NiO thin films for their application as electrocatalyst

• Glycine is used as a suitable complexing agent to maintenance ions Ni2 + in aqueous solution at pH > 6.
• A new method of synthesis of NiO by electrodeposition from Ni(II)-glycine-water system at different pH values is reported.
• Grain size and band gap energy of NiO films depend on electrolytic solution's pH.
• Nanostructures of NiO obtained in alkaline conditions are more suitable for PEC water splitting.
• Higher photoresponse is due to vacancies and the smaller grain size of NiO.

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 °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.

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