Enhanced electrolytic generation of oxygen gas at binary nickel oxide–cobalt oxide nanoparticle-modified electrodes

This study addresses the enhancement of the oxygen evolution reaction (OER) on glassy carbon, Au, and Pt electrodes modified with binary catalysts composed of nickel oxide nanoparticles (nano-NiO_x) and cobalt oxide nanoparticles (nano-CoO_x). Binary NiO_x/CoO_x-modified electrodes (with NiO_x initially deposited) show a high catalytic activity and a marked stability which far exceeds that obtained at the individual oxide-modified electrodes. This enhancement is demonstrated by a marked negative shift (more than ca. 600 mV) in the onset potential of the OER compared to that obtained at the unmodified electrodes. The modified electrodes show a significantly higher long-term stability, over a period of 5 h of continuous electrolysis, without any significant loss of activity towards the OER in alkaline medium. The influence of the solution pH, the loading level, and sequence of deposition of each oxide on the electrocatalytic activity of the modified electrodes is addressed with an aim to maximize the catalytic activity of the modified electrodes towards the OER. SEM imaging is used to disclose the size and morphology of the fabricated nano-NiO_x and nano-CoO_x binary catalysts at the electrode surface.