Oxygen Evolution Reaction Activity in IrO _x/SrIrO₃ Catalysts: Correlations between Structural Parameters and the...

Understanding how structural properties affect the oxygen evolution reaction (OER) of a catalyst can reveal important information not only on the catalytic mechanism but also on the general design strategy of OER catalysts. We report a variation of ∼0.15 V in the overpotential of the recently discovered IrO _x/SrIrO₃ OER catalysts, which directly correlates with the structural parameters of the as-synthesized SrIrO₃ epitaxial films. This variation is caused by both extrinsic area enhancement and intrinsic electronic structure modification driven by defect formation. These correlations not only indicate that microscopic film defects play an important role in the activity of the IrO _x/SrIrO₃ catalyst but also provide readily accessible parameters predictive of the activity post-transformation to IrO _x/SrIrO₃. Establishing strong associations between the catalytic activity and key structural and electronic parameters, rather than synthetic variables, provides important guidance to control and study these complex catalysts independent of the synthetic technique.