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Gregory Forcherio1 Jonathan Boltersdorf1 Asher Leff1 David Baker1 Cynthia Lundgren1

1, U.S. Army Research Laboratory, Adelphi, Maryland, United States

Plasmonic harvesting of solar energy to drive off-grid fuel generation is hindered by reaction selectivity, short (~100 fs) hot electron lifetimes, and catalyst stability. Au nanorods allow reaction specificity under solar irradiation via their tunable localized surface plasmon resonance (LSPR) and can be synthesized in gram-level quantities. This work exploits the longitudinal LSPR of Au nanorods to photodeposit Pt at targeted locations as a co-catalyst to expand hot electron lifetimes and promote reactant desorption. Time-resolved reaction kinetics between (i) the Pt(IV) precursor and (ii) plasmonic hot electrons at the Au nanorod surfaces were monitored by transmission UV-vis spectroscopy. The method is amenable to other metallic precursors. Discrete dipole computation of the Pt-decorated Au nanorods allow a priori design of photocatalysts with optimal energetics. These efforts provide a foundation towards economical manufacturing of plasmon-sensitized, bimetallic photoanodes that can spatially target specific photochemical reactions, such as C-C bond cleavage during ethanol oxidation.

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