Applicable Descriptors under Weak Metal-Oxygen d–p Interaction for the Oxygen Evolution Reaction

The oxygen evolution reaction (OER) plays a crucial role in water electrolysis and renewable energy conversion processes. Descriptors are utilized to elucidate the structure-performance relationships of OER catalytic materials, yet each descriptor exhibits specificity to particular systems. Currently, there is a lack of effective descriptors to describe the relationship between electronic structure and OER performance in ionic systems. This study reveals for the first time that widely used OER descriptors, the d-band center and charge transfer energy, are limited in their effectiveness for oxide systems dominated by ionic bonds, in which ionic interactions significantly enhance or suppress the catalytic activity. Furthermore, composite descriptors tailored for ionic systems are proposed, with findings extended to complex multi-component and high-entropy oxides. The results indicate that the metal d-band unoccupied states parameter and the active states parameter can serve as effective OER descriptors for ionic catalytic materials. This work addresses the gap in OER descriptors for ionic systems, offering a new theoretical foundation and guidance for the development of efficient OER catalytic materials.