Influence of process parameters on electrochemical and physical properties of sputtered iron-doped nickel oxide thin films

The iron-doped nickel oxide films used as oxygen evolution catalysts in the photoelectrochemical production of hydrogen from solar energy were deposited by means of RF reactive magnetron sputtering from a Ni-Fe alloy target in oxygen and argon atmosphere. The effects of processing parameters on the film properties, such as overpotential, composition, surface morphology and preferred orientation, were investigated. The electrochemical experiment, structural and compositional measurements indicate that the relative lower substrate temperature, higher RF power, higher working pressure and oxygen content are necessary to gain lower overpotential. The lowest overpotential of 251 mV is obtained at a current density of 80 mA/cm2. The existence of iron, which acts as activity site, and Ni3+ ion is responsible for lowering overpotential. By analyzing SEM and XRD data, it is also noticed that an improvement in crystallinity, appropriate grain size and less crystalline phase contribute to an increased electrocatalytic activity in oxygen evolution reaction. These results mentioned above indicate that iron-doped nickel oxide is promising as an oxygen catalyst.