Recent Developments of Atomically Dispersed Metal Electrocatalysts for Oxygen Reduction Reaction†

Comprehensive Summary Oxygen reduction reaction (ORR) is the pivotal portion in many electrochemical energy conversion and storage technologies. However, the complex mechanisms and sluggish kinetics of ORR have also become one of the key issues hindering the development and application of these technologies. Recently, single‐atom catalysts (SACs) with well‐defined atomic active centers and theoretical 100% atomic utilization have attracted broad interests in the area of electrocatalytic ORR. The electrocatalytic ORR performance of SACs is fundamentally determined by the intrinsic activity of the single‐atom active site and increasing the number of active sites involved in the ORR can further enhance the ORR activity of SACs. In this review, advances in atomically dispersed metal electrocatalysts for ORR in the last three years are summarized. Three main regulation strategies for achieving SACs with excellent intrinsic activity in the context of the ORR mechanism are involved including modulation of coordination environments, the construction of intrinsic defects, and the introduction of dual active sites. Moreover, discussions on improving the loading and utilization of active sites are given. Finally, the current challenges and opportunities for the development of SACs for ORR are presented.