The effect of nickel salt source and anion of electrolyte on electro-driven water oxidation activity using nickel hydroxide thin film

In this approach, we demonstrate a very simple, easy and fast electrodeposition method to form nickel hydroxide (Ni(OH)2) thin film which is able to catalyze the water electro-oxidation reaction. Cyclic voltammetry and bulk electrolysis with Ni(OH)2 film in aqueous solution (pH 10.0) exhibited good catalytic current. The nickel oxide film was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and voltammetric methods. The results shows that Ni(OH)2 film is a robust heterogeneous water oxidation catalyst which has been used in long time without missing efficiency. The effect of several parameters in electro-synthesize of nickel hydroxide such as the kind of nickel salts, supporting electrolyte, pH and electrodeposition time of nickel hydroxide were investigated on water oxidation efficiency. The film exhibits an overpotentials of 60 mV and 540 mV at the onset of catalytic current in borate supporting electrolyte at around 1 mA cm-2 and 10 mA cm-2 in pH 10.0, respectively. The catalytic performance of the material is demonstrated by long-term electrolysis at 1.1 V versus saturated calomel electrode (SCE) with a stable current density ~ 4.5 mA for pH 10.0 (for at least 5 h), and a Faradaic efficiency of almost 97% is obtained.