Interfacial anchoring versus surface exposure: Tuning IrOx–Co3O4 interaction for stable industrial water splitting

Developing efficient and durable electrocatalysts that minimize or eliminate Ir usage is essential for large-scale hydrogen production through proton exchange membrane water electrolysis. In this work, two IrO_x–Co₃O₄ catalysts with distinct interfacial configurations were constructed to clarify the effect of structural coupling on activity and stability. The embedded IrO_x–Co₃O₄ was prepared via a galvanic replacement-induced embedding process, while the surface-exposed IrO_x–Co₃O₄ was obtained through photo-reduction deposition. Structural analyses confirm the formation of strong Co–O–Ir linkages in embedded IrO_x–Co₃O₄, in contrast to discrete surface IrO_x nanoparticles in the exposed sample. Electrochemical measurements show that exposed–IrO_x delivers a lower overpotential of ≈ 331 mV at 10 mA cm⁻² but suffers from fast Ir dissolution, whereas embedded IrO_x maintains stable operation with a voltage of 1.78 V at 1 A cm⁻² for over 200 h in a PEM cell. In-situ Raman and DEMS results reveal that embedded IrO_x follows a dominating classical adsorbate-evolution mechanism (AEM), while exposed IrO_x–Co₃O₄ involves a lattice-oxygen-mediated mechanism (LOM), leading to its inferior stability. This work highlights that strengthening Co–O–Ir interface effectively suppresses Ir loss and provides a general strategy for designing robust Ir-based catalysts for acidic water electrolysis.