Phytic Acid-Assisted Phase Reconstruction for Co-Co₂P Heterojunction/Carbon Nanotube Oxygen Electrocatalysts for...

Rechargeable zinc-air batteries (RZABs) have high theoretical energy density but face practical limits from slow oxygen reduction/evolution reactions (ORR/OER) at air cathodes. Herein, a novel strategy integrating dual-coordination-directed growth and in situ phase reconstruction to synthesize heterostructured Co-Co₂P embedded in N, P-codoped carbon nanotubes (CNTs). The melamine-PEG-phytic acid nanosheets serve as multifunctional sources for simultaneous carbonization, N doping, and phosphorus incorporation. Using coordination polymers as precursors, controlled CNT growth and precise modulation of phytic acid concentration/calcination temperature enable phase-selective reconstruction of metallic Co and semiconducting Co₂P, forming heterointerfaces with built-in electric fields. X-ray absorption spectroscopy and DFT calculations reveal that interfacial charge redistribution of the CNT warped Co- Co₂P heterojunction creates electron-enriched Co₂P surfaces for enhanced O₂ adsorption, while positively charged Co sites accelerate OH^- oxidation kinetics. The optimized Co-Co₂P@CNT catalyst shows superior bifunctional activity, achieving an OER overpotential of 1.61 V and an ORR half-wave potential of 0.86 V 0.1 m KOH; the assembled RZAB delivers a peak power density of 192 mW cm^-2 and sustains stable cycling for 1193 h with minimal voltage decay. This work establishes a universal coordination-competition method for designing heterogeneous structured materials, offering new insights for advanced energy conversion systems.