A Stable Imide-Linked Metalphthalocyanine Framework with Atomically Dispersed Fe-N4 Sites and Ultrafine Nickel Oxide Nanoparticles to Boost Reversible Oxygen Electrocatalysis with a Record-Low ΔE of 0.59 V

Abstract

Metallophthalocyanines (MPcs) hold great promise in the electrochemical reduction of oxygen; however, their practical applications in energy storage and conversion are still limited by their low stability and poor water oxidation activity. Herein, a novel stable 2D imide-linked metalphthalocyanine framework (denoted as FePc-PI) is reported, that has atomically dispersed Fe-N₄ sites deposited on the KB substrate via in situ growth, followed by incorporation of ultrafine nickel oxide nanoparticles (NiO_x@FePc-PI/KB) to induce bifunctional electrocatalytic activities for the oxygen reduction reaction and oxygen evolution reaction. Benefitting from the robust aromatic backbone, the engineered catalytic centers, and the unique electronic structures owing to the interaction between the Fe-N₄ sites and NiO_x species, the newly developed NiO_x@FePc-PI/KB catalyst exhibits excellent reversible oxygen bifunctional activity (E_1/2 = 0.926 V, η₁₀ = 285 mV), delivering a record-low overpotential difference (ΔE) of 0.59 V, which far exceeds the noble-metal-based Pt/C+RuO₂ benchmark (ΔE = 0.77 V) and represents the highest level for reported bifunctional electrocatalysts. Furthermore, the rechargeable aqueous Zn-air batteries assembled with the NiO_x@FePc-PI/KB catalyst deliver a high peak power density of 232.9 mW cm⁻² and long-term cycling durability over 1400 cycles. Flexible all-solid-state Zn-air batteries exhibit stable cycling at various flat/bent/flat states, thus demonstrating their excellent prospects in realistic implementations.