Interfacial States in Au/Reduced TiO₂ Plasmonic Photocatalysts Quench Hot-Carrier Photoactivity

Understanding the interface of plasmonic nanostructuresis essentialfor improving the performance of photocatalysts. Surface defects insemiconductors modify the dynamics of charge carriers, which are notwell understood yet. Here, we take advantage of scanning photoelectrochemicalmicroscopy (SPECM) as a fast and effective tool for detecting theimpact of surface defects on the photoactivity of plasmonic hybridnanostructures. We evidenced a significant photoactivity activationof TiO2 ultrathin films under visible light upon mild reductiontreatment. Through Au nanoparticle (NP) arrays deposited on differentreduced TiO2 films, the plasmonic photoactivity mappingrevealed the effect of interfacial defects on hot charge carriers,which quenched the plasmonic activity by (i) increasing the recombinationrate between hot charge carriers and (ii) leaking electrons (injectedand generated in TiO2) into the Au NPs. Our results showthat the catalyst's photoactivity depends on the concentrationof surface defects and the population distribution of Au NPs. Thepresent study unlocks the fast and simple detection of the surfaceengineering effect on the photocatalytic activity of plasmonic semiconductorsystems.