Advances in Stabilizing Spinel Cobalt Oxide-Based Catalysts for Acidic Oxygen Evolution Reaction.

Oxygen evolution reaction (OER) is pivotal to sustainable energy storage and conversion technologies. Yet, its sluggish kinetics in acidic media and reliance on expensive noble metal catalysts limit its efficiency in these applications. Spinel cobalt(II, III) oxide (CoO)-based catalysts are cost-effective alternatives with high theoretical catalytic activity. However, their practical deployment is hindered by their poor stability in acidic electrolytes. This review critically examines recent advances in enhancing the stability of spinel CoO-based catalysts for acidic OER. The fundamental reaction mechanisms of acidic OER are first analyzed to illustrate how different catalyst design strategies can be used to improve their stability. Next, five key catalyst design strategies reported in recent studies are summarized: 1) constructing protective surface layers, 2) modulating reaction pathways, 3) controlling cobalt redox dynamics, 4) tuning cobalt-oxygen covalency, and 5) stabilizing lattice oxygen. Further, recent research progress in understanding the structure-activity-stability relationship of spinel CoO-based catalysts is summarized, with a focus on identifying their catalytically active sites, tracking surface reconstruction, and elucidating degradation mechanisms. This review ends with a discussion of future research directions for addressing key challenges in realizing durable, high-performance CoO-based catalysts for acidic OER applications.