Weak d–d coupling in iron‑cobalt tetranitro-phthalocyanine boosting oxygen electrocatalysis for high-performance flexible zinc-air batteries

Advancing flexible zinc-air batteries (ZABs) hinges on efficient bifunctional oxygen electrocatalysts, yet resolving the intrinsic activity trade-off between oxygen reduction (ORR) and evolution reactions (OER) remains a long-standing scientific challenge. Herein, we propose a molecular engineering strategy to optimize the electronic configuration of Fe centers in an iron‑cobalt tetranitro-phthalocyanine complex (FeCoPc-NO 2 ), by Co atoms and electron-withdrawing nitro groups. Density functional theory and electrochemical characterizations unveil that a weak d-d coupling between adjacent Fe/Co atoms tailors the Fe 3d-orbital electron density and the adsorption energies of oxygen-containing intermediates, boosting OER activity (η 10  = 320 mV) and concurrently retaining high ORR performance (E 1/2  = 0.81 V vs. RHE). Moreover, the assembled flexible ZABs achieve a peak power density of 74.9 mW·cm −2 , high round-trip efficiency (65.8 %), prolonged cycling stability (48 h), and mechanical robustness (>90° bending). This study validates the feasibility of atomically precise molecular design in creating bifunctional electrocatalysts with exceptional performance and cost efficiency.