Electronegativity-Driven Heterointerfaces for Water Electrolysis: Thermodynamic and Kinetic Insights into Built-In Charge Transfer.

Interfacial electronic modulation via heterostructure engineering puts forward a promising route toward effective water electrolysis. However, the mechanistic connection between atomic-scale interface design, thermodynamic stability, and device-level performance remains unresolved. Here, we report non-noble nickel-based heterostructures in which both systems outperform their pristine counterparts, defying the conventional unidirectional charge-transfer paradigm. Electronegativity-driven interfacial charge redistribution defines the activity order: NiV@NiCr-LDH/NF > NiCr@NiV-LDH/NF > NiV-LDH/NF > NiCr-LDH/NF. Guided by density functional theory and Pourbaix analysis, we identify surface-functionalized oxygen species as the true catalytic termini, with metal centers acting as electronic modulators. The interfacial electronic structure lowers reaction barriers and drives dynamic Adsorbate-mediated mechanism, as confirmed by operando impedance, temperature-dependent, and pH-dependent studies. The intrinsic activity is validated through multi-normalized turnover frequency analysis, alongside ∼95.1% for hydrogen evolution reaction and 93% for oxygen evolution reaction Faradaic efficiency, indicating excellent selectivity. The optimized NiV@NiCr-LDH/NF delivers low overpotentials (242 mV for OER and 144 mV for HER at 50 mA cm-2) and achieves ∼1.539 V at 10 mA cm-2 with 140 h stability. Importantly, these insights translate to practical systems, single-stack anion exchange membrane water electrolyzer, seawater electrolysis, and solar and battery-driven hydrogen production, offering a predictive framework for high-activity, robust overall water electrolysis, and establishing a mechanistically grounded blueprint for scalable hydrogen generation.