MnxCo3-xO4 spinel oxides as efficient oxygen evolution reaction catalysts in alkaline media

The design of efficient electrocatalysts for oxygen evolution reaction (OER) is an essential task in developing sustainable water splitting technology for the production of hydrogen. In this work, manganese cobalt spinel oxides with a general formula of MnxCo3-xO4 (x = 0, 0.5, 1, 1.5, 2) were synthesised via a soft chemistry method. Non-equilibrium mixed powder compositions were produced, resulting in high electrocatalytic activity. The oxygen evolution reaction was evaluated in an alkaline medium (1 M KOH). It was shown that the addition of Mn (up to x <= 1) to the cubic Co3O4 phase results in an increase of the electrocatalytic performance. The lowest overpotential was obtained for the composition designated as MnCo2O4, which exhibited a dual-phase structure (similar to 30% Co3O4 + 70% Mn1.4Co1.6O4): the benchmark current density of 10 mA cm(-2) was achieved at the relatively low overpotential of 327 mV. The corresponding Tafel slope was determined to be similar to 79 mV dec(-1). Stabilities of the electrodes were tested for 25 h, showing degradation of the MnCo2O4 powder, but no degradation, or even a slight activation for other spinels. (C) 2020 The Author(s). Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.