Nickel-mediated dynamic interfaces of dual spillover pathways in Mo₂C/Ni/Fe₃O₄ for water splitting

Abstract

Developing efficient bifunctional electrocatalysts for sustainable water splitting necessitates precise interfacial engineering to overcome competing adsorption energetics and charge transfer limitations. Herein, we propose a nickel-mediated interfacial design in Mo₂C/Ni/Fe₃O₄ ternary heterostructures that establishes decoupled hydrogen-containing intermediates/oxygen-containing intermediates spillover pathways via synergistic lattice matching and orbital hybridization based on the interfacial Ni-C-Mo and Ni-O-Fe interaction and moderation. The electronic architecture leverages metallic Ni (Φ = 5.0 eV) as a mediator between metalloid Mo₂C (Φ = 4.6 eV) and Fe₃O₄ (Φ = 5.2 eV), establishing a unidirectional charge transfer pathway via the gradient work function (Φ) profile. Theoretical and experimental analyses reveal that the Ni interlayer orchestrates three critical functions: (1) gradient work function alignment (4.6→5.0→5.2 eV) reduces interfacial Schottky barriers by 67% via multi-step electron tunneling; (2) electronegativity-driven charge polarization (ΔχNi-Mo = +0.25, ΔχNi-Fe = +0.08) creates dual-active zones (electron-rich Ni-Mo₂C and hole-enriched Ni-Fe₃O₄), optimizing adsorption energetics (ΔGH* = -0.37 eV, ΔG*OH = -0.34 eV) through d-band center unification (-2.50 eV); (3) lattice strain engineering minimizes mismatch from 7.2% to 3.8%, enabling exceptional durability (>150 h). The catalyst achieves record bifunctional performance with ultralow overpotentials (η₁₀ = 80 mV for hydrogen evolution, 228 mV for oxygen evolution) and 97.4% Faradaic efficiency at industrial current densities, while maintaining pH-resilient Nernstian behavior. This work establishes a universal paradigm for designing adaptive catalytic interfaces through targeted orbital hybridization, bridging atomic-scale charge dynamics with macroscopic reactor performance for sustainable hydrogen production.