Overall alkaline water electrolysis over active, stable, low loading iridium catalysts sputtered on nickel foam

Cost-effective, active, and durable electrodes are required for the development of the efficient alkaline water electrolysis towards green hydrogen production. Here, we report successful fabrication of such electrodes by means of robust radio frequency magnetron sputtering that produces uniform, crystalline, and phase pure catalytic iridium thin films over nickel foam current collectors. The effect of working pressure of argon gas during sputtering on the physicochemical and electrochemical properties of the as-fabricated electrodes has been investigated. Specifically, it has been established that the employment of working pressure of 3 Pa afforded the electrodes with the lowest mass loading of precious iridium metal (approximate to 0.32%), but exhibiting the best alkaline water electrolysis performance. The electrodes demonstrated favourable overpotentials of 14 mV and 318 mV at current densities of +/- 10 mA/cm2 toward hydrogen (HER) and oxygen (OER) evolution reactions, respectively. Furthermore, as a cathode and an anode for overall water splitting (OWS) in alkaline electrolyte, the electrode exhibited the cell voltage of 1.57 V at 10 mA/cm2 and stably performed electrolysis at different applied current densities. The electrochemical performance of the electrodes has been corroborated by work function measurements using Kelvin probe force microscopy.