Bioinspired Oxygen-Evolution Reaction: Achieving Oxygen-Evolution Reaction on Layered Manganese-Oxide Surface with Extremely Low Overpotential

Despite the common belief that manganese (hydr)oxides in the absence of other metal ions require high overpotential to catalyze the oxygen-evolution reaction (OER) in alkaline conditions, our study has uncovered surprising results. Layered manganese oxide demonstrates noteworthy OER activity at the Mn(III) to Mn(IV) oxidation peak following charge accumulation. This activity is achieved with remarkably low overpotential (120 mV) in a 1.0 M KOH solution. Initially, the Faraday efficiency is a modest 20%, which can be attributed to initial charge storage. However, as the reaction continues (200 s), the efficiency significantly increases to over 80%. We also propose a detailed mechanism for OER in this low-overpotential regime, supported by in situ visible and Raman spectroscopies of the Mn(III) to Mn(IV) peak and the surrounding OER region. By examining the amount of oxygen generated and the concentrations of redox-active Mn ions near the redox peak, a turnover frequency of 3.8 × 10–3 s–1 at 1.35 V was calculated. The reduced overpotential observed during the OER can be attributed to the complex interplay between the OER process and charge accumulation as it was observed in nature, with these factors collectively enabling a notably low overpotential. These findings provide significant insights for the design and development of highly efficient and stable electrocatalysts for OER in water-splitting applications, potentially revolutionizing approaches to energy conversion and storage. Our findings have significant implications for the development of highly efficient and stable electrocatalysts for OER in water-splitting applications.