Nickel-mediated dynamic interfaces with 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 intermediate/oxygen-containing intermediate spillover pathways via synergistic lattice matching and orbital hybridization based on the interfacial Ni–C–Mo and Ni–O–Fe interactions 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 tunnelling; (2) electronegativity-driven charge polarization (Δχ_Ni–Mo = +0.25, Δχ_Ni–Fe = +0.08) creates dual-active zones (electron-rich Ni–Mo₂C and hole-enriched Ni–Fe₃O₄), optimizing adsorption energetics (ΔG_H* = −0.37 eV and 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 and 228 mV for oxygen evolution) and 97.4% faradaic efficiency at industrial current densities, while maintaining pH-resilient Nernstian behaviour. 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.