Mn-Induced Support Stabilization and Ir Electronic Activation Enable Acid-Stable, Low-Loading IrO₂ Water Oxidation

The practical application of low-iridium catalysts for the acidic oxygen evolution reaction (OER) is primarily constrained by the intertwined issues of inadequate activity and stability. Incorporation of Mn into such low-iridium catalysts is effective, yet the underlying mechanism remains unclear. This study addresses the mechanistic role of Mn doping in enhancing the activity and stability of low-loading IrO₂/Co₃O₄ catalysts. By incorporating Mn³⁺ into the octahedral sites of Co₃O₄, Mn induces strong Mn─O covalency that reinforces the spinel lattice and stabilizes ultra-low-loading IrO₂ nanoparticles, delivering a 51 mV reduction in overpotential and a six-fold enhancement in operational stability compared to its undoped counterpart at a current density of 10 mA cm⁻². In situ spectroscopic analyses and theoretical calculations decipher the dual role of Mn: it reinforces lattice integrity through strong covalent Mn─O bonds, suppressing ion leaching, while concurrently activating the Ir sites via interfacial Mn─O─Ir electron transfer, which optimizes intermediate adsorption and promotes the efficient oxide-path mechanism (OPM). This work demonstrates that the targeted dual-regulation of support chemistry establishes a general principle for designing high-performance, low-loading IrO₂ catalysts for acidic OER.