Interfacially Engineered Transition Metal Phosphide Heterostructure for Zinc–Air Battery-Driven Hydrogen Production Coupled with Benzyl Alcohol Oxidation

The development of advanced functional electrocatalysts that couple energy storage with chemical conversion requires precise control over interfacial electronic structure and reaction energetics. Herein, we report an interfacially engineered transition-metal phosphide heterostructure composed of Ni2P and FeP, encapsulated within nitrogen-doped graphitic carbon (Ni2P/FeP@NC), which exhibits excellent activity toward bifunctional oxygen electrocatalysis, hydrogen evolution, and benzyl alcohol oxidation. The heterostructured architecture promotes interfacial charge redistribution and modulates the adsorption energies of key reaction intermediates, resulting in enhanced intrinsic activity and favorable kinetics. Electrocatalytic investigations reveal that the heterostructured catalyst (i) promotes a dominant four-electron oxygen reduction reaction (ORR) pathway, delivering a half-wave potential of 0.84 V and a limiting current density of ∼6 mA cm–2; (ii) achieves the benchmark current density for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at low overpotentials; and (iii) facilitates the selective oxidation of benzyl alcohol to benzoic acid. The narrow potential gap between ORR and OER underscores the catalyst’s suitability for rechargeable zinc–air batteries (ZABs). When employed as the air cathode, the heterostructured catalyst delivers a high peak power density of 170 mW cm–2, excellent charge–discharge rate capability, and remarkable long-term cycling stability exceeding 600 h. A solid-state ZAB fabricated using the same catalyst likewise exhibits competitive energy-storage performance. Furthermore, by exploiting the multifunctional electrocatalytic activity of the heterostructure, a ZAB-powered coupled water electrolysis system enables sustained hydrogen evolution with the selective oxidation of benzyl alcohol to benzoic acid, demonstrating a self-powered platform that seamlessly integrates electrochemical energy storage with value-added chemical production.