Local Hollandite Phase Inducing Oxygen Path Mechanism Enables Durable PEM Electrolysis.

Abstract

Large-scale proton-exchange-membrane water electrolyzers (PEMWEs) are urgently needed for green hydrogen production, however, their development is largely hindered by the use of high-loading iridium in the anode. While amorphous IrO_x catalysts with high activity exist, they typically follow either the lattice oxygen mechanism compromising stability, or the adsorbate evolution mechanism suffering from a high overpotential limit. Oxide path mechanism (OPM) offers a promising alternative by enabling direct ^*O─^*O coupling, but its activation in the pure IrO_x system remains challenging given the long distance between adjacent Ir atoms. Herein, we report a class of (La)IrO_x porous amorphous catalyst with OPM pathway, featuring local unconventional hollandite phase and abundant water molecules inside its lattice tunnels. We demonstrate that such a unique short-range ordered structure can induce shortened Ir-Ir_edge distance and highly-active Ir^≥5+ species, both contributing to desirable OPM for greatly enhanced catalytic performances. The as-assembled PEMWE achieves a cell voltage of 1.62 V at 1 A cm^-2 with a low loading of 0.2 mg_Ir cm^-2, and can operate stably over 500 h at industry-level current density. The accelerated stress test further validates its durability advantage at even lower 0.1 mg_Ir cm^-2 loading, which validates its potential as a viable anode solution for durable low-iridium PEMWEs.