Advances of earth-abundant cobalt-based single-atom catalysts for acidic oxygen evolution by electrolysis
Abdur Rehman Nasrullah, Ziheng Zhou, Abdul Rehman, Muhammad Safdar Hussain, Xiaobo Zheng, Yongan Yang, Ligang Wang
Abstract
The oxygen evolution reaction (OER) is critical for sustainable energy technologies, including proton exchange membrane water electrolyzers (PEMWEs) and metal-air batteries. However, its implementation in acidic media remains constrained by sluggish kinetics, high energy barriers, and reliance on scarce noble-metal catalysts. Cobalt-based single-atom catalysts (Co-SACs) have emerged as a breakthrough solution, combining exceptional catalytic activity, stability, and atomic utilization efficiency. Its superior acidic OER performance stems from the electronic structure of low-spin Co<sup>3+</sup> centers, which optimize t<sub>2</sub>g-π orbital interactions with oxygen intermediates. This configuration promotes efficient surface reconstruction and thermodynamically favorable adsorption of OER species, accelerating reaction kinetics. Tailored coordination environments, engineered via supports like nitrogen-doped carbons, graphene, or metal oxides, can further modulate Co electronic and spin states, enhancing activity and durability. This review systematically analyzes advancements in Co-SAC design, elucidating correlations between atomic coordination, electronic properties, and catalytic mechanisms. Advanced synthesis methods and characterization tools are evaluated to discuss structure-activity relationships of Co-SAC. Finally, we address current challenges and future research directions that involve computational modeling, multi-metallic SAC architectures, and operando techniques to guide the rational design of high-performance Co-SACs. Addressing these challenges will accelerate the commercialization of PEMWEs for cost-effective green hydrogen production.