Two-dimensional 1T-phase Mn_xIr_1-xO₂ for high-performance acidic oxygen evolution reaction

Proton exchange membrane water electrolysis (PEMWE) is regarded as the most promising technique for the sustainable production of green hydrogen due to its multiple advantages such as high working current density and high hydrogen purity. However, the anodic oxygen evolution reaction (OER) has a significant impact on the overall efficiency of the electrolytic water reaction due to its sluggish kinetics, which has prompted the search for catalysts possessing both high activity and durability. Iridium oxide exhibits excellent stability under acidic conditions but has poor catalytic activity, leading to its inability to meet the strict requirements of large-scale industrial applications. In this work, we have successfully synthesized two-dimensional (2D) 1T-phase manganese-iridium oxide (1T-Mn_0.8Ir_0.2O₂) nanosheets by a molten-alkali mechanochemical method. In 0.5 M H₂SO₄, the 1T-Mn_0.8Ir_0.2O₂ achieves an overpotential of 274 mV with a low Tafel slope of 70.77 mV dec^-1, and durable stability of 75 h at 10 mA cm^-2. Its mass activity at 1.5 V vs. reversible hydrogen electrode (RHE) is 390 mA mg_Ir^-1, 39.6 times higher than that of commercial iridium oxide. When applied in a practical PEMWE system, 1T-Mn_0.8Ir_0.2O₂ retains a high current density of 1000 mA cm^-2 at a cell voltage of 1.7 V for 500 h. The 1T-Mn_0.8Ir_0.2O₂ catalyst can achieve high performance and endurance of PEMWE with only a small amount of Ir, providing a feasible approach to alleviate the problems of low Ir reserves and high prices.