Local atomic structural descriptor and crystal field determined Ru1− <i>x</i> Ir <i>x</i> O2 as oxygen evolution catalyst unifying stability and activity

Ru/Ir oxides represent the promising catalysts of oxygen evolution reaction (OER) with better stability than Ru oxides and lower overpotentials than Ir oxides. To elucidate the activity and stability mechanisms of Ru1-xIrxO2 at an acceptable computation cost, the proposed local atomic structural descriptors are used to predicate OER intermediate adsorption ability and solvation effect accurately, and the cluster expansion (CE) method is applied to determine the ground state at given Ir concentration. Further analysis shows that Ru-O-Ir local configuration is the atomic fingerprint of Ru1-xIrxO2 structures, unifying both OER activity and stability. Crystal field analysis reveals that the Ru atom makes the dz2 band center of the Ir site atom upshift to achieve weak *OOH adsorption for high OER activity, while Ir atoms effectively lower the t2g orbital of the Ru atom to stabilize the structures. Our work not only addresses the activity-stability trade-off in Ru/Ir oxides but also advances the fundamental understanding of descriptor-based and CE models.