Mesoporous Mn–Fe oxyhydroxides for oxygen evolution

Abstract

The development of high-performance and Earth-abundant catalysts is imperative for the oxygen evolution reaction (OER), and mesoporous oxyhydroxides show huge potential as advanced catalysts toward the OER due to a large specific surface area and porous structure. Here, we adopt a facile template method to synthesize bimetallic Mn–Fe oxyhydroxides. meso-Mn₁Fe₁O_x shows a large BET specific surface area of 212.4 m² g⁻¹ and an average pore diameter of 13.1 nm, which favor the exposure of many active sites for the reaction. meso-Mn₁Fe₁O_x exhibits excellent OER performance with a low overpotential of 275 mV at 10 mA cm⁻², a small Tafel slope of 52 mV dec⁻¹, and good long-term stability, and is superior to most Mn-based electrocatalysts. Kinetic studies indicate that Fe and Mn sites should synergistically catalyze the OER. Theoretical calculations reveal that the surface doping of Fe onto MnOOH can moderately destabilize the surface bridge O atoms and promote the generation of surface oxygen vacancies that can act as highly active sites for the OER.