Plasmon-Mediated Catalytic O₂ Dissociation on Ag Nanostructures: Hot Electrons or Near Fields?

Plasmonic nanostructures have been proposed as useful materials for photon harvesting applications. However, the mechanisms by which energy transfer occurs across interfaces formed between plasmonic materials and their environment are under debate. A commonly invoked mechanism is indirect hot charge carrier transfer, where hot carriers are generated in the plasmonic material by nonradiatve plasmon decay, followed by transfer of these carriers to interfacial species in a sequential process. Alternatively, chemical interface damping has been reported to allow direct interaction between surface plasmons and interfacial species electronic states. Here we provide evidence from experiment and theory that for plasmon-mediated catalytic O2 dissociation on Ag plasmonic nanoparticles, the direct interaction of O2 molecules with surface plasmon near-fields was responsible for observed photocatalysis. These results offer important mechanistic insights for the design of plasmonic materials that maximize efficiency for promoting catalytic small molecule activation using photon fluxes.