Accelerating electron injection in NiFeOx/Co:BiVO4 via dopamine-mediated interfacial electric field for self-powered water oxidation

Polydopamine (PDA) interlayer enables ligand-bonded, electronically coupled interface for efficient charge transfer. • The photoanode displays 5.47   mA/cm 2 at 1.23 V RHE with 84.4% charge injection and 95.03% Faradaic efficiency, exhibiting excellent stability. • A triboelectric nanogenerator-electromagnetic generator (TENG-EMG) hybrid enables self-powered water oxidation under wind for off-grid H 2 production. Photoelectrochemical water oxidation is limited by sluggish interfacial charge transfer and fragile catalyst photoanode contacts. We introduce a polydopamine (PDA) interlayer that bridges NiFeOx and cobalt-doped bismuth vanadate (Co:BiVO 4 ), forming an intimate and ligand-bonded interface with strong electronic coupling. The bridge strengthens the interfacial electric field (IEF) strength, accelerates carrier separation and transfer, suppresses surface recombination, and stabilizes oxygen evolution intermediates, lowering kinetic barriers and external bias. First principles density functional theory with crystal orbital Hamilton population shows optimized adsorption at Fe sites and a reduced barrier at the rate-determining step, consistent with performance. Under air mass 1.5 global (AM 1.5   G) illumination, the optimized photoanode delivers 5.47   mA/cm 2 at 1.23   V versus reversible hydrogen electrode (vs. RHE) and 95.03% oxygen Faradaic efficiency with excellent stability. Because the electrode operates under low energy input, we demonstrate a closed-loop self-powered system in which a compact triboelectric and electromagnetic harvester, with wind-to-electricity conversion 49.5%, supplies sufficient power for continuous water splitting under ambient wind, achieving near stoichiometric gas evolution. Download: Download high-res image (295KB) Download: Download full-size image To address fossil fuel-driven environmental challenges, we developed a dual-strategy synergy for solar-driven water oxidation: external electron injection via a hybrid nanogenerator and internal interfacial engineering via a polydopamine (PDA) molecular bridge. Specifically, the PDA bridge covalently links NiFeOx and Co-doped BiVO 4 , constructing a robust heterointerface with an enhanced interfacial electric field that accelerates charge separation, suppresses recombination, and stabilizes OER intermediates. Complementing this internal optimization, a compact hybrid wind harvester provides continuous, self-powered electron injection, enabling bias-free H 2 /O 2 co-evolution at near-stoichiometric ratios under wind conditions. This synergistic approach yielded a photoanode current density of 5.47   mA/cm 2 at 1.23   V (vs. RHE) with 95% Faradaic efficiency and exceptional long-term stability. By overcoming both interfacial fragility and external power dependence, this work offers a scalable, materials-agnostic blueprint for off-grid hydrogen production in resource-limited settings.