Mechanistic Insights into Plasmonic Catalysis by Dynamic Calculations: O2 and N2 on Au and Ag Nanoparticles

Abstract

Plasmonic metal nanoparticles offer an interesting alternative to traditional heterogeneous catalytic processes due to their ability to harness energy from light. While plasmonic photocatalysis is a well-known phenomenon, the exact mechanism of these reactions is still debated. Understanding the precise workings of plasmon-driven reactions is crucial for the rational design of novel catalytic structures. Here, we utilize real-time, time-dependent density functional theory (RT-TD-DFT) to excite systems with oscillating electric fields and track the subsequent excited state dynamics in real time. We find that RT-TD-DFT with Ehrenfest dynamics gives results that are consistent with experimental tests of plasmonic excitations, in that the presence of nanoparticles facilitates light-induced molecular dissociation. Our results also demonstrate that the electric-field enhancement is the primary driving factor for the plasmon-driven dissociation of O2 on Au and Ag nanoparticles, while for N2 dissociation, both charge transfer and field enhancement appear to play important roles. Additionally, charge density and density of states calculations indicate that these excitations are π → π* on short time scales and a mixture of π, σ → π*, σ* over time.