Oxidation−Stable Plasmonic Copper Nanoparticles in Photocatalytic TiO2 Nanoarchitectures

Tuesday, 3 October 2017: 12:00
National Harbor 6 (Gaylord National Resort and Convention Center)
P. A. DeSario, J. Pietron, T. Brintlinger, J. F. Parker (U.S. Naval Research Laboratory), O. A. Baturina (Naval Research Laboratory), R. Stroud, and D. R. Rolison (U.S. Naval Research Laboratory)
We describe the incorporation of plasmonic copper (Cu) nanoparticles into titania (TiO2) aerogels and demonstrate surface plasmon resonance (SPR)–driven photoelectrochemical oxidation of methanol under visible light. Copper could provide a more abundant, less expensive alternative to gold and silver as a visible light–active plasmonic metal, however, the propensity of Cu to oxidize at the expense of its plasmonic character greatly limits its potential applications. Most reports of supported, plasmonic Cu nanoparticles describe the necessity of preventing Cu oxidation by maintaining strictly anoxic environments or relying on surface-obscuring chemical stabilizers. We stabilize plasmonic Cu nanoparticles by establishing extensive interfacial contact between Cu nanoparticles and a TiO2 aerogel support. The multiple points of contact between 2–3 nm Cu nanoparticles photodeposited at the networked ~10 nm TiO2 particulates of the aerogel stabilizes Cu against oxidation to an extent that preserves the plasmonic behavior of the nanoparticles, even after long-term exposure to ambient air. The wavelength dependence of photoelectrochemical methanol oxidation at Cu/TiO2 aerogel photoanodes verifies the plasmonic origin of the photoelectrochemistry. Plasmonic behavior is not seen for Cu photodeposited at a commercially available, non-networked TiO2 nanopowder in which the primary particle size is ~10× greater than the size of the supported Cu particle. The divergent behavior of Cu when a 3D Cu||oxide interface is formed on aerogel supports compared to the 1D junction between Cu on commercial TiO2 nanopowder supports highlights the importance of the interfacial design motif on preserving plasmonic Cu.