LAUSR

Developing effective descriptors for perovskite oxygen evolution reaction (OER) electrocatalysts is crucial for advancing clean energy technologies, which are often constrained by incomplete theoretical calculations. Herein, using step‐wise strained (−3–3%) NdNiO3 as a model, the density functional theory (DFT) is employed, considering both bulk superlattice model (B‐model) and surface slab models (S‐model) to garner a set of electronic descriptors. The S‐model‐derived metal─oxygen orbital hybridization is found to agree with the X‐ray absorption spectroscopy (XAS) results, which, however, are disentangled from the observed OER activity trend. Further detailed analysis discovers that the alignment of the calculated O 2p band position with the OER redox potential on an absolute scale can serve as a hitherto unexplored descriptor for comprehending the activity of lattice oxygen and its bonding strength to OH*. Combined DFT and XAS data reveals that excessive strain hinders surface oxygen exchange, slows down the rate‐determining step of OH* adsorption, and impairs the durability of the electrocatalyst by altering the random electron occupancy in frontier orbitals. The work sheds light on the rational design of cost‐effective, high‐performance perovskite‐based electrocatalysts.