Covalent Dangling of Poly-Indium-Phthalocyanine Over Carbon Nanopits as Superior Oxygen Reduction Catalyst for Flexible Zn-Air Battery.

Abstract

Oxygen reduction reaction (ORR) represents a cornerstone in renewable energy technologies such as Zn-air batteries, yet its sluggish kinetics and reliance on noble metal catalysts remain critical bottlenecks. Here, we report an ingenious catalyst configured by covalently dangling poly-indium-phthalocyanine onto carbon nanopit defects in carbon nanotubes (InPPc/v-CNTs). This architecture induces axial In-C coordination that disrupts the symmetric electron distribution of the planar In-N₄ center and strengthens electronic metal-support interactions. Theoretical calculations reveal that this distorted electronic environment enhances O₂ adsorption/dissociation kinetics while weakening the *OH desorption energy barrier, thereby synergistically boosting ORR kinetics. Benefiting from the tailored electronic structure and optimized metal-support configuration, InPPc/v-CNTs exhibits both superb ORR activity and stability, with a half-wave potential up to 0.90 V vs RHE and a kinetic current density of 42.9 mA cm^-2 (>10-fold higher than the Pt/C benchmark). Moreover, in aqueous Zn-air batteries, it delivers a remarkable power density of 270 mW cm^-2 and a discharge stability up to 865 h at 5 mA cm^-2. This work transcends conventional catalyst design by unifying defect engineering, electronic asymmetry, and macromolecular stabilization into a cohesive framework, establishing a new paradigm for metal phthalocyanine-based ORR catalysts.