Unraveling the Effects of Atomic Cluster and Transition‐Metal Oxide Support on the Superior Oxygen Reduction Reaction Performance of Single Atom Catalysts

Abstract Co has been widely adopted as a substitute for Fe in constructing single atom catalysts (Co‐SAC) for oxygen reduction reaction to eliminate Fenton reaction. However, Co‐SAC still suffers from significant deactivation due to its high H 2 O 2 production. In this paper, Co atomic cluster (Co AC) and ZrO 2 are successfully composited to Co‐SAC to form Co‐SA/AC@ZrO 2 . This catalyst achieves a half‐wave potential of 0.88 V and retains 95.2% of its current density after 60 hours of durability test, outperforming all the recently reported catalysts utilizing Co as the active site. Calculations and in situ experiments reveal that the superior performance can be attributed to Co AC and ZrO 2 , which causes the upshift in the dz 2 , dxz and dyz orbitals of the Co single atom, thereby enhancing the adsorption of *OOH and thus suppressing H 2 O 2 production. More importantly, it is discover that the stability of catalysts is also highly correlated with the adsorption difference energy of *O and *OOH ( ΔE ad/*O‐*OOH ). This correlation is further validated by comparing Co‐SA/AC@TiO 2 and Co‐SA/AC@HfO 2 . These findings offer new insights into the electronic factors governing both activity and stability, enabling the rational design of durable single atom catalysts for practical ORR applications.