CAS: Photocatalysis on Hybrid Plasmonic Materials

With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Suljo Linic of University of Michigan is studying photochemical transformations on metal nanoparticles. These nanoparticles strongly absorb sunlight. It was recently shown that they can photolytically drive chemical transformations when illuminated with sunlight through a process known as plasmonic catalysis. The interest in the field is rooted in the fact that, in contrast to conventional thermally driven chemical reactions on metals, photoreactions on these nanoparticles present the possibility of providing higher efficiencies and product selectivity. Specifically, the Linic group is studying the hypothesis that the plasmonic catalysis of these nanoparticles can be optimized for high rates and selectivities through specific design of their surface composition and structure. The proposal promises to advance our understanding of using solar energy to drive chemistry in an environmentally sustainable and energy efficient manner. Professor Linic and his students will be involved in educational activities, such as development of a sustainable energy course, and multiple outreach efforts directed at underrepresented students in science. Under this award, Professor Suljo Linic and his team at the University of Michigan are studying chemical reactions on plasmonic metal nanoparticles. These nanoparticles are characterized by a resonant excitation of localized surface plasmon resonance (LSPR) when illuminated with solar intensity UV-vis light. It has been demonstrated that under the LSPR conditions, these nanoparticles can activate hot electron (hole)-driven chemical reactions at meaningful rates, and in contrast to conventional thermally driven chemical reactions on metals, where energy is indiscriminately dumped into every available reaction coordinate (and controlling product selectivity is challenging), the LSPR-driven reactions offer the opportunity to efficiently deposit energy into select reaction coordinates leading to high efficiencies and product selectivity. The central hypothesis of the project is that optimal plasmonic materials, allowing for higher reaction rates and product selectivity, are plasmonic single atom alloy (SAA) nanoparticles with a relatively large plasmonic (Ag or Au) nanoparticle (10s of nm), augmented with isolated single atoms of other metals (Pt, Pd, Rh, Ru) in the surface layer of the plasmonic nanoparticle. The SAAs are potentially an optimal marriage of the light harvesting potential of plasmonic nanoparticles and the chemical activity of the single atoms. It is postulated that these structures would allow us to control the resonant energy flow at the nanoscale, funneling energy efficiently and selectively in specific and desired chemical transformations. The proposal will test this hypothesis by: (i) synthesizing plasmonic SAA and characterizing their geometry, (ii) studying the flow of optical energy in these materials at nanoscales and (ii) testing these plasmonic SAA nanostructures in a number of steady state catalytic processes where the product selectivity is of critical importance. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.