Abstract: Oxygen evolution reaction (OER) is a pivotal half-reaction in electrocatalytic water splitting and metal-air batteries. Non-precious metal heterointerface materials provide significant advantages in enhancing OER activity while reducing costs; however, effective engineering of built-in electric fields (BIEFs) at multi-phase heterointerfaces remains a major challenge. Herein, we report a novel FeNi/Mo₂‚C@NC multi-phase heterointerface catalyst synthesized via a low-temperature solution combustion method followed by high-temperature annealing. The catalyst exhibits a heterointerface between FeNi and Mo₂C, while nitrogen-doped carbon (NC) coating interacts further with FeNi and Mo₂C to form Mott-Schottky heterointerfaces and generate multiple BIEFs that promote charge separation, optimize Fermi levels and fine-tune d-band centers, thereby modifying the adsorption behavior of oxygen-containing intermediates during the OER process. This strategy drives the directional migration of charge carriers along multiple pathways, resulting in rapid charge transfer, enhanced conductivity, and a synergistic improvement in OER performance. The FeNi/Mo₂C@NC catalyst shows exceptional OER activity, with a low overpotential of 242 mV at a current density of 10 mA cm^-2, a Tafel slope of 68 mV dec^-1 derived from steady-state chronoamperometry testing, and excellent catalytic stability over 200 h. This study underscores the importance of engineering multi-phase heterointerfaces and multiple BIEFs to enhance the OER performance of catalysts.

Key words: Low-temperature solution combustion, Multi-phase heterointerfaces, Carrier migration enhancement, Fermi levels modulation, D-band center tuning