Indirect to Direct Charge Transfer Transition in Plasmon-Enabled CO Photoreduction.

Understanding hot carrier dynamics between plasmonic nanomaterials and its adsorbate is of great importance for plasmon-enhanced photoelectronic processes such as photocatalysis, optical sensing and spectroscopic analysis. However, it is often challenging to identify specific dominant mechanisms for a given process because of the complex pathways and ultrafast interactive dynamics of the photoelectrons. Here, using CO reduction as an example, the underlying mechanisms of plasmon-driven catalysis at the single-molecule level using time-dependent density functional theory calculations is clearly probed. The CO molecule adsorbed on two typical nanoclusters, Ag and Ag , is photoreduced by optically excited plasmon, accompanied by the excitation of asymmetric stretching and bending modes of CO . A nonlinear relationship has been identified between laser intensity and reaction rate, demonstrating a synergic interplay and transition from indirect hot-electron transfer to direct charge transfer, enacted by strong localized surface plasmons. These findings offer new insights for CO photoreduction and for the design of effective pathways toward highly efficient plasmon-mediated photocatalysis.