Potassium-sulfur batteries hold practical promise for next-generation batteries because of their high theoretical gravimetric energy density and low cost. However, significant impediments are the sluggish K2S oxidation kinetics and a lack of atomic-level understanding of K2S oxidation. Here, for the first time, we report the catalytic oxidation of K2S on a sulfur host with Co single atoms immobilized on nitrogen-doped carbon. On the basis of combined spectroscopic characterizations, electrochemical evaluation, and theoretical computations, we show a synergistic effect of dynamic Co-S and N-K interactions to catalyze K2S oxidation. The resultant potassium-sulfur battery exhibited high capacities of 773 and 535 mAh g-1 under high current densities of 1 and 2 C, respectively. These findings provide atomic-scale insights for the rational design of highly efficient sulfur hosts.