Quantifying plasmonic hot carrier charge transfer in photoelectrochemical systems*

We measure the IQE of plasmon-derived hot carrier charge transfer to drive chemical reactions at a plasmonic gold working electrode in aqueous electrolyte. At positive applied potential, we oxidize ascorbic acid through transfer of hot holes and at negative applied potential, electron transfer drives the hydrogen evolution reaction (HER).

Furthermore, we measure the IQE as a function of plasmon energy both on- and off-resonance, using the Kretschmann-Raether method to control the resonance condition. Through this method we are able to deduce the role of the plasmon in hot-carrier photocatalysis. We find that IQE is flat on- and off-resonance and therefore the plasmon acts as a photoabsorber.

Recent experiments have shown plasmon-enhanced C_x:H₂ selectivity under CO₂-reduction conditions. However, the role the plasmon plays is not well understood. The instrument described provides a platform to probe the plasmonic mechanistics. As a test case, this work studies one hypothesis that plasmonic hot carriers may be implicated.