Photoelectrochemical Hydrocarbon Oxidation Augmented By Plasmonic Nanostructures

Abstract

Solar energy can be absorbed via surface plasmon resonance (SPR) to promote excitation of energetic, or “hot”, charge carriers that can be locally transferred or thermally dissipated to augment photocatalytic processes. The “hot” carriers can selectively drive energy-intensive photoelectrochemical reactions at low temperatures by activating adsorbed reactants and accelerating surface kinetics. Plasmonically-sensitized nanocatalysts were investigated for their photocatalytic and photoelectrochemical oxidation of ethanol, with an emphasis on carbon-carbon bond cleavage, under solar simulated-light irradiation. Material approaches included the (i) SPR-functionalization of a traditional metal oxide semiconductor (TiO2) and (ii) bimetallic nanocatalysts composed of epitaxially photodeposited catalytic Pd at targeted locations on plasmonic Au nanorods. Results are correlated with nanocatalyst morphology, composition, and homogeneity to maintain SPR-induced charge separation and mitigate carbon monoxide poisoning. Ensemble photoelectrochemical measurements were complimented with single-particle dark-field scattering and photoluminescence spectroscopies to understand the extraction and utilization of SPR-excited “hot” carriers. Ethanol oxidation was achieved, yielding a solar-driven method for low temperature, complete photo-oxidation of complex hydrocarbons via plasmonic photocatalysis.