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.

Plasmonic catalysis provides a possible means for driving chemical reactions under relatively mild conditions. Rational design of these systems is impeded by the difficulty in understanding the electron dynamics and their interplay with reactions. Real-time, time-dependent density functional theory (RT-TDDFT) can provide dynamic information on excited states in plasmonic systems, including those relevant to plasmonic catalysis, at time scales and length scales that are otherwise out of reach of many experimental techniques. Here, we discuss previous RT-TDDFT studies of plasmonic systems, focusing on recent work that gains insight into plasmonic catalysis. These studies provide insight into plasmon dynamics, including size effects and the role of specific electronic states. Further, these studies provide significant insight into mechanisms underlying plasmonic catalysis, showing the importance of charge transfer between metal and adsorbate states, as well as local field enhancement, in different systems.