Electrochemical Imaging of Photoanodic Water Oxidation Enhancements on TiO₂ Thin Films Modified by Subsurface Aluminum Nanodimers

Detecting metal plasmonic enhancements on the activity of semiconducting photoanodes for water oxidation is often obscured by the inherent electroactivity and instability of the metal in electrolyte. Here, we show that thin TiO₂ photoanodes modified by subsurface Al nanodimers (AlNDs) display enhancements that are consistent with plasmon modes. We directly observed enhancements by mapping the oxygen evolution rates on TiO₂/AlND patterns using scanning electrochemical microscopy (SECM) while exciting the surface plasmons of the nanodimers. This study highlights the importance of sample configuration for the in situ characterization of metal/photoanode interactions and suggests a route for Al-based plasmonics applied to photoelectrochemistry.