Paracrystalline IrCoO_x stabilization by rutile SnO₂ towards durable acidic oxygen evolution

The development of oxygen evolution reaction catalysts featuring high activity with long-term durability in acidic media remains a major challenge for proton exchange membrane water electrolysis. Herein, we report a strategy to stabilize highly active paracrystalline IrCoO_x phase by integrating it with rutile SnO₂, achieving an optimal activity-durability balance. The formation of paracrystalline phase, directly visualized by in-situ heating transmission electron microscopy, enhances lattice oxygen activation and oxygen evolution kinetics. Owing to their shared P4₂/mnm space group, the resulting IrCoO_x-2@SnO₂ catalyst demonstrates a mass activity of 1192 A g_Ir^-1 (114 times that of IrO₂), and a durable operation for 3880 h at 2 A cm^-2 in electrolysis cell, representing a very competitive stability under the identical conditions. The SnO₂ was proven to stabilize the paracrystalline phase by mitigating metal dissolution, agglomeration, and Ir over-oxidation, while favorable interfacial water dynamics enables reversible oxygen species cycling and efficient proton transfer, collectively contributing to the satisfactory durability.