Sulfur-bridge ligands altering the microenvironment of single-atom CoN3S sites to boost the oxygen reduction reaction.

We report here an asymmetric N,S-coordinated cobalt-based single-atom catalyst with sulfur (S)-bridge ligands (Co-N/S-C) for the oxygen reduction reaction (ORR). The Co-N/S-C exhibits a half-wave potential (E1/2) of 0.908 V versus RHE, outperforming most state-of-the-art ORR catalysts. Theoretical calculations indicate that the CoN3SC10-S moiety facilitates the ORR kinetics by optimizing the adsorption of intermediates. This work provides new insights into the design of single-atom catalysts for electrocatalysis through heteroatom-bridge ligand engineering.