Interfacial hydrogen-bond engineering of PVP–bridged WO3/TiO2 for efficient solar-driven cathodic metal protection

Durable photocathodic protection is an effective approach to mitigate marine metal corrosion, but its performance often suffers from rapid charge recombination and poor band-edge matching of semiconductors. Herein, a hydrogen-bond-mediated molecular bridging strategy is proposed by incorporating polyvinylpyrrolidone (PVP) as a multifunctional interlayer into a WO 3 /TiO 2 heterojunction. 1 H solid-state NMR and theoretical calculations reveal that the carbonyl groups of PVP preferentially form strong hydrogen bonds with surface bridging hydroxyl (Ti–OH) groups, modulating the interfacial structure at the molecular scale. The PVP-engineered WO 3 /TiO 2 interface passivates surface trap states, promotes interparticle charge migration, and induces an interfacial dipole field that shifts the band edges to more negative potentials. These synergistic effects enhance both carrier dynamics and the thermodynamic driving force for electron injection into the protected metal. The optimized WO 3 /PVP/TiO 2 photoelectrode delivers a photocurrent density of 62.5 μA·cm -2 and a cathodic polarization potential of -482 mV ( vs . Ag/AgCl), 2.1-fold and 1.2-fold higher than the PVP-free WO 3 /TiO 2 counterpart, and maintains a polarization potential of approximately -252 mV in darkness after 12 hours of illumination, ensuring long-term protection of 304 stainless steel. This interface design concept offers guidance for engineering efficient, durable photoelectrodes for corrosion protection and related photocatalytic applications. Molecular-scale interface engineering is achieved by introducing a PVP interlayer into WO 3 /TiO 2 . Hydrogen bonding with bridging hydroxyls passivates trap states, enables orbital hybridization, and induces an interfacial dipole, thereby enhancing carrier dynamics and band energetics. This strategy highlights hydrogen-bond modulation as a versatile route to efficient, durable photoelectrodes for photocathodic protection and solar-driven applications. • PVP molecular bridge creates H-bonded interfaces in WO 3 /TiO 2 heterojunction. • NMR and DFT reveal selective H-bonding with Ti–OH bridging hydroxyl surface sites. • H-bonding passivates recombination traps and tunes band edges via dipole fields. • WO 3 /PVP/TiO 2 achieves 62.5 μA cm -2 and sustained "all-weather" metal protection.