Spectroscopic Characterization of the Surface of Multifunctional Bimetallic and Plasmonic Catalysts
Abstract
The design of new active and selective catalysts for challenging chemical transformations is critical for addressing a range of pressing scientific challenges, including sustainable chemical production, renewable energy generation, and remediation of toxic chemical products. Visible light illumination of metal nanoparticles can be used to achieve catalytic selectivity and activity that is not possible in classic thermal reactions. In 2018, the Army Research Office funded a research project in the PIÕs laboratory to study plasmon-assisted (light-driven) reactions on metal nanoparticles to improve product selectivity in both materials synthesis and catalysis. The funded work focuses on hybrid materials composed primarily of a plasmonicÑbut less catalytically activeÑmetal with a small amount of a poorly plasmonicÑbut more reactiveÑmetal. The work aims to use visible light excitation of the core metal to drive highly selective catalytic transformations at the interface between the two metals. The project also includes the study of light-driven reactions on monometallic silver nanomaterials to understand the role of crystalline defects in plasmon-assisted catalytic processes. Thus far, the PIÕs research group has developed a plasmon-assisted approach to selectively enhance the rate of platinum ion reduction and deposition onto a plasmonic silver nanoparticle core, thereby overcoming key challenges in bimetallic nanoparticle synthesis. This method also enables the generation of silver-core/platinum-satellite nanostructures with platinum localized at the tips of silver bipyramids or triangular nanoprismsÑan architecture that is not currently achievable using traditional thermal particle synthesis approaches. This architecture is promising for catalytic applications because it localizes a catalytically active metal, platinum, at the tips of plasmonic silver nanostructures, which is the location where the enhancing effects of light illumination are strongest. The group has also begun studies into plasmon-assisted catalysis and has modified an existing thermal flow reactor for gas phase reactions to accommodate lightassisted reactions. These modifications have included the installation of a temperature-controlled reaction cell with a window for visible light illumination as well as the construction of light sources from light emitting diodes with narrow wavelength ranges that together span the visible region of the spectrum. To understand the mechanisms of these light-driven catalytic reactions on metal nanostructures, it is important to characterize the structure and composition of the plasmonic nanoparticle catalysts post-synthesis, during a catalytic reaction, and post-reaction. This DURIP proposal requests funds for a diffuse reflectance infrared Fourier transform spectrometer (DRIFTS) and associated components, such as a DRIFTS reaction cell, to enable the study of molecules adsorbed at the surface of the nanoparticles at each stage of the catalyst evaluation process. Understanding what molecules are adsorbed at the surface under particular conditions is crucial to elucidating reaction mechanisms and to designing catalyst materials with ideal performance. The PIÕs group will use this instrumentation to study the role of adsorbed capping agents from materials synthesis on catalyst activation and reactivity, as well as the effect of plasmonic excitation on the binding strength of reactants and intermediates in reactions of interest, such as selective partial hydrogenation and partial oxidation reactions. Together with available microscopy and spectroscopy tools for the characterization of metal nanoparticle structure and composition, this DRIFTS instrumentation for characterizing molecular adsorbates will enable the PIÕs group to make significant advances in the design of multifunctional nanomaterials with catalytic performance that is tailorable using visible light.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 07, 2021
- Source ID
- W911NF2110292
Entities
People
- Michelle L Personick
Organizations
- Army Contracting Command
- Office of the Secretary of Defense
- Wesleyan University