Wrinkled Ir-MnOx nanospheres as pH-universal electrocatalysts for oxygen evolution reaction

Abstract

The oxygen evolution reaction (OER) is an essential anode reaction paired with various energy conversion processes including hydrogen evolution, CO₂ reduction and nitrate reduction under diverse pH conditions, and its sluggish kinetics limits the overall energy efficiencies of those processes due to the lack of highly efficient OER electrocatalysts. Herein, we report wrinkled Ir-doped MnO_x (Ir-MnO_x) nanospheres as advanced OER electrocatalysts over a wide pH range (0–14). Benefiting from the wrinkled nanospherical morphology with a large specific area and optimal electronic structure, the resulting Ir-MnO_x shows low overpotentials of only 270, 295, and 360 mV at 10 mA cm⁻² under acidic, alkaline and neutral conditions, respectively. Specifically, a high Ir mass activity of 1335.7 A g_Ir⁻¹ at 1.5 V vs. RHE under acidic conditions can be achieved. Systematic experiments and operando spectroscopy characterization as well as density functional theory (DFT) calculations reveal that integrating Ir into MnO_x leads to a modulated electronic structure for optimal intermediates adsorption, and their synergy prevents the migration/aggregation of Ir species and the peroxidation of MnO_x substrates, jointly beneficial to improve the OER activity and stability.