(294f) Pulsed Photon Illumination to Control Catalytic Chemistry at a Metal Nanoparticle Surfaces

Visible photon excitation of metal-adsorbate interfaces can facilitate specific reaction pathways that are not possible via thermal excitation. However, details of how photons influence the energetics of specific elementary steps on metal surfaces as a function of photon wavelength have not been resolved. This lack of insight hinders the process of identifying catalyst compositions and photon wavelengths that would optimize specific catalytic chemistries. Furthermore, recent theoretical predictions have suggested that the ability to transiently manipulate the energetics of individual elementary steps in a catalytic process may provide the ability to significantly promote rates and selectivity. However, there exists only minimal understanding of how adsorbate and reactive intermediate population on functioning catalysts change transiently in response to the introduction or removal of a photon flux.

In this talk we will address both of these missing insights and use them to guide the design of catalytic processes that are optimized through the introduction of pulsed photon illumination. We experimentally extracted the influence of photon wavelength on adsorbate binding energies on metal nanoparticle surfaces by pairing CO temperature programmed desorption (TPD) experiments with visible light exposure on Pt and Pd nanoparticle surfaces. The results suggest that wavelength specific photon illumination can be used to control specific adsorbate-metal bond activation in-situ. We apply these insights to investigate the prospect of dynamic pulsed light illumination of supported metal catalysts to synthesize acetic acid (CH₃COOH) directly from CH₄ and CO₂, a reaction that has only been demonstrated using pulsed reactant flows.