Oxygen-Evolution Reaction on Nickel Oxyhydroxide’s Surface: Toward a Super Catalyst for Oxygen-Evolution Reaction with Ultralow Overpotentials

This study challenges the conventional understanding of nickel (hydr)oxides as inefficient catalysts for oxygen-evolution reaction (OER) under alkaline conditions. It is demonstrated that nickel oxyhydroxide, characterized by several methods, forms on Ni foam's surface and exhibits OER activity at extremely low potentials. This activity becomes particularly notable at the peak of Ni(II) oxidation to Ni(III), which follows charge accumulation. Remarkably, this mesoporous, super hydrophilic, and high-surface-area catalyst requires a minimal overpotential, as low as 130 mV, with a current density of 200 μA/cm2, and displays a Tafel slope of 77.9 mV/decade in alkaline media (0.10 M KOH). Considering the amount of oxygen produced and the concentration of redox-active Ni ions in the redox peak region, the turnover frequency was calculated to be 1.1 × 10–3 s–1 at a potential of 1.36 V. Achieving these parameters at such a remarkably low overpotential holds significant promise. This study also proposes a mechanism for OER at this low overpotential, based on in situ Raman spectroscopic analysis of the Ni(II) to Ni(III) oxidation peak and the OER region. The observed low overpotential for OER can be attributed to the complex interplay between the OER process and the phenomenon of charge accumulation. All these factors result in an exceptionally low overpotential for OER. Our findings hold profound implications for the development of highly efficient and stable electrocatalysts for OER, particularly in water-splitting applications. This research not only expands our understanding of nickel oxyhydroxide as a potential OER catalyst but also opens avenues for future exploration in electrocatalysis.