Quantifying the Ultrafast and Steady-State Molecular Reduction Potential of a Plasmonic Photocatalyst

04 October 2023, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Plasmonic materials are promising photocatalysts as they are well-suited to convert light into hot carriers and heat. Hot electron transfer is suggested as the driving force in many plasmon-driven reactions. However, to date there are no direct molecular measures of the rate and yield of plasmon-to-molecule electron transfer, or energy of these electrons on the timescale of plasmon decay. Here, we use ultrafast and spectroelectrochemical surface-enhanced Raman spectroscopy to quantify electron transfer from a plasmonic substrate to adsorbed methyl viologen molecules. We observe a reduction yield of 2.4 - 3.5 % on the picosecond timescale, with plasmon-induced potentials ranging from -3.1 to -4.5 mV. Excitingly, some of these reduced species are stabilized and persist for tens of minutes. This work provides concrete metrics toward optimizing material-molecule interactions for efficient plasmon-driven photocatalysis.

Keywords

Photocatalysis
Ultrafast Spectroscopy
Electron Transfer
Surface Enhanced Raman Spectroscopy
Plasmonics

Supplementary materials

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Supplementary Material
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List of Supplementary Materials: -Sample Preparation -Spectroelectrochemical SERS Instrumentation -Ring Deformation Peak Ratio Calculation -Ultrafast SERS Instrumentation -Data Collection and Analysis -DFT Calculations of MV -MV Surface Concentration Estimation -SI Figures: S1 – S12 -SI Tables: S1 – S5 -References 51-54
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