Engineering Proton-Coupled Electron Transfer to Break Activity-Stability Trade-Off of Oxygen Electroreduction...

Single-atom catalysts (SACs) are regarded as effective electrocatalysts for oxygen reduction reaction (ORR). However, integrating high active and long-term durability on SACs is still challenging due to the severe limitations of the activity-stability trade-off. Herein, we report an integrative electrocatalyst combining isolated Fe sites and MoC nanoparticles (MoC/Fe─NC). MoC nanoparticles accelerate ORR kinetics via the proton-feeding effect and optimize Fe site microstructure. Thus, MoC/Fe─NC exhibits a high alkaline ORR activity with half-wave potential (E_1/2) of 0.916 V versus the reversible hydrogen electrode, and exceptional durability of 50k cycles with 5 mV E_1/2 loss. The observed ORR performance is further verified in a zinc-air battery (ZAB) with a high peak power density of 316 mW cm^-2 and operational stability over 1000 h. Moreover, the fabricated temperature-adaptive quasi-solid-state ZAB can cycle stably for 150 h under alternating temperatures. Theoretical calculations and experiment characterizations, involving scanning electrochemical microscopy techniques and distribution of relaxation times analysis, reveal that the excellent capabilities of MoC/Fe─NC arise from accelerated proton-coupled electron transfer, weakened *OH adsorption, and strengthened Fe─N bonds fueled by MoC nanoparticles. This work sheds light on breaking the activity-stability trade-off barrier of SACs for energy-conversion applications.