Encaging Co nanoparticle in atomic Co-N₄-dispersed graphite nanopocket evokes high oxygen reduction activity for flexible Zn-air battery

Rational design of oxygen reduction reaction (ORR) electrocatalysts with indestructible active sites for highperformance Zn-air batteries (ZABs) remains a significant challenge. Herein, we achieve an innovative active site design by encaging Co nanoparticles within the Co-N-4 atomic sites-dispersed graphite nanopocket (Co-SAsNPs/NC), leading to outstanding alkaline ORR activity and stability, and consequently ultra-high power density of 193.8 mW cm-2 and specific capacity of 819.1 mAh gZn(-1) at 10 mA cm(-2) of a primary ZAB assembled, along with impressive power density of 73.4 mW cm(-2) and charging/discharging stability up to 110 cycles of a flexible solidstate ZAB. Theoretical calculations unveil the enhanced ORR kinetics can be traced to the significantly optimized local electronic structure of Co-N-4 sites with upshifted d-band center and reduced energy barrier of rate-limiting step by the encaged Co nanoparticle. This study showcases a creative conformational design for guiding the construction of valid synergy in hybridized metal/single-atom catalysts.