Ensemble atomic sites for acidic oxygen evolution: mechanisms, atomic engineering, and AI-assisted screening

Atomically dispersed metal catalysts (ADMCs), featured with maximized atom efficiency and well-defined active sites, have attracted increasing research interest, especially for addressing the critical challenges of the oxygen evolution reaction (OER), including slow kinetics, limited stability, and dependence on scarce noble metals. From isolated atomic centers to multi-metallic ensemble atomic sites (EAS), spatially coupled metal centers with distinct atomic configurations offer a new platform for tailoring the energetics of OER pathways. EAS provide cooperative interactions that can modulate intermediate binding energies, enable multi-electron transfer, and enhance structural resilience under work conditions. In this review, we summarize recent progress in the mechanistic understanding of EAS in acidic OER (AOER) over the past three years, highlight advances in material synthesis strategies, and explore how artificial intelligence and machine learning are accelerating the discovery of optimal ensembles. We propose future directions for rational catalyst design and advocate the integration of advanced characterizations and data-driven modeling to realize next-generation AOER catalysts.