(698c) Mechanistic Insights into Plasmonic Photocatalysis By Dynamic Calculations

Many industrial chemical processes require high operating temperatures to drive catalytic reactions which are crucial to human development. These high temperatures are both energy demanding and detrimental to the long term life of the catalyst. Plasmonic metal nanoparticles offer an interesting alternative to traditional heterogenous catalytic processes due to their ability to be activated by light. While plasmonic photocatalysis is a well-known event, the exact mechanism of these reactions is still debated. Understanding the precise workings of plasmon transfer is important for rational design of novel catalytic structures. Here, we utilize real-time, time-dependent density functional theory (RT-TD-DFT) to excite a system with oscillating electric fields and track the subsequent excited state dynamics in real time. This method models light of varying frequency in order to observe the mechanism of plasmon-mediated reactions in Au and Ag nanoparticles. We find that RT-TD-DFT with Ehrenfest dynamics gives results consistent with experimental tests of plasmonic excitations, in that the nanoparticle presence facilitates light-induced molecular dissociation. Furthermore, we believe our results demonstrate that the near-field enhancement is a critical factor for the plasmonic driven dissociation of O₂ and N₂ on Au and Ag nanoparticles. Lastly, calculating the electric field in the regions of space around the nanoparticle allows us to observe where the greatest field enhancement occurs. By using dimers, or other arrangements of nanoparticles, we show how these plasmonic systems can be tuned to drive selective chemistry in biomass conversion through the targeted activation of C-O bonds, and in related chemical processes.