Strong light–matter interactions in Au plasmonic nanoantennas coupled with Prussian blue catalyst on BiVO4 for photoelectrochemical water splitting

A facial and large‐scale compatible fabrication route is established, 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 interactions 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 through the injection of sub‐band‐gap hot electrons. To substantiate the activity of the photoanodes, the interfacial electron dynamics are significantly improved by using a PBA water oxidation catalyst (WOC) resulting in an 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, whereas it was boosted to 295 μA cm−2 and 1800 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.