Intrinsically robust cubic MnCoOx solid solution: achieving high activity for sustainable acidic water oxidation

Abstract

This article reveals the promising potential of MnCoO_x solid solutions as an effective catalyst for the oxygen evolution reaction (OER). The solid oxide solution was synthesized by utilizing redox deposition of KMnO₄ and Co(NO₃)₂ on a carbon paper (CP) support with varying Co/Mn ratios. XRD and TEM analyses confirmed the homogeneous distribution of Co and Mn species in MnCoO_x. According to OER tests in acid electrolyte, the catalytic efficiency of Mn₁Co₅O_x surpassed that of Co₃O₄, MnO_x, and IrO₂, demonstrating overpotentials of 275 and 569 mV at a current density of 10 and 100 mA cm⁻², respectively. The investigation emphasizes the crucial roles of Co³⁺ and Mn⁴⁺ cations as well as oxygen vacancies (O_v) sites in facilitating the OER mechanism. These essential characteristics were duly observed in a Mn₁Co₅O_x solid solution catalyst. Furthermore, the introduction of a Mn dopant contributed to the durability of Mn₁Co₅O_x in acidic OER, thereby exhibiting outstanding catalytic stability for nearly 300 hours at 100 mA cm⁻² current density. In addition, DFT studies provided insight into how Mn₁Co₅O_x enhances the catalytic performance of the OER. In conclusion, this study offers valuable insight into designing efficient OER catalysts using MnCoO_x solid solutions as a promising candidate.