Coordination Asymmetry Stabilizes a Low-Iridium Cobalt Spinel Oxide Anode for Durable Proton-Exchange Membrane Water...

Low-iridium cobalt spinel oxides are promising anode catalysts for proton-exchange membrane water electrolyzers (PEMWEs), but their practical application remains limited by the structural instability of Ir-O-Co motifs at high current densities. Here, we show that the simultaneous incorporation of Mn and Ir into the octahedral (O_h) sites of Co₃O₄ to form Ir_0.1Co_1.93Mn_0.97O₄ markedly enhances both acidic oxygen evolution activity and durability. In contrast to the single-doped analogues, in which Mn is predominantly stabilized as Jahn-Teller-active Mn³⁺ in Co₂MnO₄ and Ir exists as less oxidized Ir^>4+ in Ir_0.1Co_2.9O₄, Ir_0.1Co_1.93Mn_0.97O₄ exhibits an optimized local coordination environment with Jahn-Teller-suppressed Mn⁴⁺ and high-valence Ir^>4+ species at the O_h sites. This distinctive local coordination chemistry enhances structural robustness while promoting catalytic activity under operating conditions. In a practical PEMWE, Ir_0.1Co_1.93Mn_0.97O₄ sustains stable operation for 2800 h at 0.5-1.0 A cm^-2, outperforming most reported low-Ir-loading catalysts. This work highlights the importance of coordination asymmetry in the design of durable electrocatalysts for clean energy conversion.