Extremely Active and Robust Ir-Mn Dual-Atom Electrocatalyst for Oxygen Evolution Reaction by Oxygen-Oxygen Radical Coupling Mechanism

A novel Ir-Mn dual-atom electrocatalyst is synthesized by a facile ion-exchange method by incorporating Ir in SrMnO₃, which yields an extremely high activity and stability for the oxygen evolution reaction (OER). The ion exchange process occurs in a self-limitation way, which favors the formation of Ir-Mn dual-atom in the IrMnO₉ unit. The incorporation of Ir modulates the electronic structure of both Ir and Mn, thereby resulting in a shorter distance of the Ir-Mn dual-atom (2.41 Å) than the Mn-Mn dual-atom (2.49 Å). The modulated Ir-Mn dual-atom enables the same spin direction O (↑) of the adsorbed ^*O intermediates, thus facilitating the direct coupling of the two adsorbed ^*O intermediates to release O₂ via the oxygen-oxygen radical coupling mechanism. Electrochemical tests reveal that the Ir-SrMnO₃ exhibits a superior OER’s activity with a low overpotential of 207 mV at 10 mA cm^-2 and achieves a mass specific activity of 1100 A g_Ir^-1 at 1.5 V. The proton-exchange-membrane water electrolyzer with the Ir-SrMnO₃ catalyst exhibits a low electrolysis voltage of 1.63 V at 1.0 A cm^-2 and a stable 2000-h operation with a decay of only 15 μV h^-1 at 0.5 A cm^-2.