Synergistic Engineering of Local Coordination and Electronic Modulation by CoS x Nanoparticles Dictates the Oxygen Reduction Pathway of Cobalt Single‐Atom Catalysts in Acidic Media

ABSTRACT The selectivity of the oxygen reduction reaction (ORR) is critical for energy transformation efficiency of metal–air batteries or the synthesis of hydrogen peroxide. Hence, we report a coordination‐engineering strategy for cobalt single‐atom (CoSA) catalysts anchored on carbon nanotubes, which enables accurate adjustment of the coordination structure of Co centers via sulfur doping. By modulating the first coordination shell (Co─N x S y ), the two‐electron reduction ORR pathway on CoSA can be facilitated. Specifically, the Co─N 2 S 2 –coordinated catalyst (CoS@CoSA/NS‐CNT/CC) achieves an onset potential of 0.73 V with average Faraday efficiency (FE) of H 2 O 2 for 88% within the 0.35–0.55 V potential window. In contrast, the catalyst with Co─NS 3 coordination (CoS 2 @CoSA/NS‐CNT/CC) exhibits a higher onset potential of 0.78 V but a lower FE of H 2 O 2 for only 48%. Through combined theoretical and experimental analyses, including XAS and in situ ATR‐FTIR, we demonstrate that sulfur doping modulates the electronic configuration of CoSA, thereby optimizing the adsorption behavior of the *OOH intermediate, leading to > 90% H 2 O 2 selectivity and showcasing performance that compares favorably with the top‐tier catalysts known for acidic electrosynthesis of H 2 O 2 .