Alloy-Single Atom Synergy: FeCo Nanoparticles Modulating FeN _<i>x</i> Sites for Enhanced Bifunctional Oxygen Catalysis in Ultrastable (3000+ h) Zinc-Air Batteries

Zinc-air batteries, widely regarded as a frontrunner in sustainable energy storage solutions, struggle with performance constraints stemming from the insufficient activity and durability of bifunctional oxygen electrocatalysts. This research presents a composite catalyst (FeCo@Fe-N-CNTs) synthesized through a straightforward in situ growth method, effectively integrating FeCo alloys with Fe single atoms incorporated in nitrogen-doped carbon nanotubes (N-CNTs). Theoretical and experimental studies show that FeN_<i>x</i> atoms weaken the interaction between active iron sites and reactants, enhancing the reaction energy optimization. The optimization improves the characteristics of the intermediates' adsorption and desorption, enabling the catalyst to exhibit remarkable bifunctional activity under alkaline conditions, achieving an overall overpotential as low as 0.67 V, with overpotential of merely 290 mV for the oxygen evolution process. The performance boost stems from a 38% larger electrochemical surface area (ECSA) combined with an 18% lower charge transfer resistance (<i>R</i>_ct), pointing to gains in both active site numbers and intrinsic catalytic efficiency. We also employed X-ray absorption spectroscopy (XAS) and in situ Raman measurements to probe the Fe-N_<i>x</i> bonding configuration and track how the surface changes under the working conditions. Notably, zinc-air batteries using dual-function catalyst reached a peak energy density of 894 mAh g^-1, maintained stable cycling for over 3000 h, and exhibited consistent charge-discharge capabilities in flexible quasi-solid-state devices (with voltage fluctuation remaining under 5% during bending strain), highlighting its immense potential for practical use in creating compact, high-capacity rechargeable batteries that can be worn or carried around. It is like giving us the keys to unlock a world where we can seamlessly incorporate portable energy solutions for renewable energy projects.