Strong Light-matter Interaction in Au Plasmonic Nanoantennas Coupled with Prussian Blue Catalyst on BiVO4 for Photoelectrochemical Water Splitting.

We establish a facial and large scale compatible fabrication route affording a high performance heterogeneous plasmonic-based photoelectrode for water oxidation that incorporates a CoFe-Prussian blue analog (PBA) structure as the water oxidation catalytic center. For this purpose, an angled deposition of gold (Au) was used to selectively coat the tips of the bismuth vanadate (BiVO4) nanostructures, yielding Au capped BiVO4 (Au-BiVO4). The formation of multiple size/dimension Au capping islands provides strong light-matter interaction at nanoscale dimensions. These plasmonic particles not only enhance light absorption in the bulk BiVO4 (through the excitation of Fabry-Perot (FP) modes) but also contribute to photocurrent generation via the injection of sub-bandgap hot electrons. To substantiate the activity of the photoanodes, the interfacial electron dynamics is significantly improved using a PBA water oxidation catalyst (WOC) resulting in Au-BiVO4/PBA assembly. At 1.23 V vs RHE, the photocurrent value for a bare BiVO4 photoanode was obtained as 190 µA cm-2, while it was boosted to 295 µA cm-2, and 1,800 µA cm-2 for Au-BiVO4, and Au-BiVO4/PBA, respectively. Our results suggest that this simple and facial synthetic approach paves the way for plasmonic-based solar water splitting, in which a variety of common metals and semiconductors can be employed in conjunction with catalyst designs.