Beyond sunlight: A molecular “bridge” protects metals from rust, day and night

Despite its potential for marine corrosion control, photocathodic protection (PCP) suffers from a persistent bottleneck: the conflict between thermodynamic driving forces and charge kinetics. While WO₃/TiO₂ type-II heterojunctions facilitate energy storage, they typically sacrifice reduction potential and face sluggish transport due to surface defects. To date, it has remained a significant challenge to develop a molecular approach that resolves this impasse by simultaneously amplifying the driving force and accelerating kinetics through defect passivation.

Here, we propose a “hydrogen-bond-mediated molecular bridge” strategy by introducing flexible polyvinylpyrrolidone (PVP) into the WO₃/TiO₂ interface. We demonstrate that PVP carbonyl groups preferentially hydrogen-bond with bridging hydroxyls on TiO₂. This interaction not only passivates surface defects but also induces an interfacial dipole field. The resulting electrostatic field shifts the conduction band edge (−0.88 V), amplifying the driving force for electron injection while preserving efficient charge transfer.

This work provides a generalizable paradigm for utilizing soluble polymers to tune inorganic interfaces and achieves “round-the-clock” protection, maintaining a protective potential for over 12 h in darkness. The work entitled “Interfacial hydrogen-bond engineering of PVP–bridged WO₃/TiO₂ for efficient solar-driven cathodic metal protection” was published in Advanced Powder Materials (Available online on 17 February 2026).