Structural impacts on the degradation behaviors of Ir-based electrocatalysts during water oxidation in acid

Large-scale hydrogen production by electrocatalytic water splitting still remains as a critical challenge due to the severe catalyst degradation during the oxygen evolution reaction (OER) in acidic media. In this study, we investigate the structural impacts on catalyst degradation behaviors using three iridium-based oxides, namely SrIrO₃, Sr₂IrO₄, and Sr₄IrO₆ as model catalysts. These Ir oxides possess different connection configurations of [IrO₆] octahedra units in their structure. Stable OER performance is observed on SrIrO₃ and attributed to the edge-linked [IrO₆] structure and rapid formation of a continuous IrO_x layer on its surface, which functions not only as the "real" catalyst but also a shield preventing continuous cation leaching (with <1.0 at.% of Ir leaching). In comparison, both Sr₂IrO₄ and Sr₄IrO₆ catalysts demonstrate quick current fading with structure transformation to rutile IrO₂ and formation of inconducive SrSO₄ precipitates on surface, blocking the reactive sites. Nevertheless, over 60 at.% of Ir leaching is detected from the Sr₄IrO₆ catalyst due to its isolated [IrO₆] structure configuration. Results of this work highlight the structural impacts on the catalyst stability in acidic OER conditions.