Activating rare-earth single-atom catalyst by second-shell sulfur doping for efficient oxygen reduction catalysis

Rare-earth single-atom catalysts (SACs) hold great promise for the oxygen reduction reaction (ORR) due to their Fenton-inert character and distinctive electronic structure. However, their practical application is hindered by excessively strong adsorption of ORR intermediates and a rigid coordination environment. To address this, we develop a second-shell sulfur coordination engineering strategy and fabricate a nitrogen-sulfur co-doped carbon-supported lanthanum SAC (La/SNC) with a well-defined La-N 6 -S 2 configuration via ammonia-assisted vapor deposition. Density functional theory calculations demonstrate that second-shell sulfur doping promotes electron transfer from La to N, reinforcing hybridization between La 5d and N 2p orbitals. This optimized electronic structure not only weakens the adsorption of ORR intermediates but also raises the metal dissolution energy, thereby synergistically boosting both ORR activity and long-term stability. Experimentally, La/SNC delivers a high half-wave potential of 0.897 V in 0.1 M KOH and maintains 96% of its initial current after 40 hours of continuous operation. When assembled into zinc-air batteries, La/SNC achieves a peak power density of 139.1 mW cm -2 and an energy density of 887 Wh kg Zn -1 , surpassing commercial Pt/C. This work offers a practical design principle for advanced rare-earth SACs and deepens mechanistic insight into second-shell coordination for regulating electrocatalytic performance. • 1.This work pioneers a second-shell coordination design for rare-earth single-atom catalysts, achieving a unreported La–N 6 –S 2 configuration. • With second-shell S coordination, La/SNC catalyst delivers considerably superior ORR activity, markedly outperforming commercial Pt/C. • The S-modulated La 5d–N 2p hybridization fine-tunes oxygen intermediate adsorption and enhances structural stability.