Tailoring Energy Transfer from Hot Electrons to Adsorbate Vibrations for Plasmon-Enhanced Catalysis

Chemical reactions can be enhanced on surfaces of bimetallic nanoparticles composed of a core plasmonic metal and a catalytically active shell when illuminated with light. However, the atomic-level details of the steps that govern such photochemical reactions are not yet understood. One critical process is the non-adiabatic energy transfer from hot electrons that transiently populate the unoccupied electronic orbitals of the adsorbate to the vibrational modes of the adsorbed reactants. This occurs via electron-vibration coupling and could potentially be tailored by changing the composition of the shell. Here, we apply an ab initio method based on density functional theory to investigate this coupling at various sp- and d-band metal-adsorbate interfaces. Our calculations demonstrate the importance of d-bands in enhancing and tuning this energy transfer at the interface. Further, they highlight specific choices of metals that could be utilized as shells for efficient photochemical reactions. From these calculations, we extract a simple descriptor (dependent on the coupling matrix element and equilibrium bond length) that can account for the coupling strength at a metal-adsorbate interface, thus representing a valuable tool for rational shell design for different reactions. We show the utility of this descriptor for photocatalysis with calculations for a specific photochemical reaction. The introduction of this descriptor should also impact other processes such as light-triggered drug release that exploit hot electrons, and surface-enhanced Raman spectroscopy, where electron-vibration coupling plays a key role.