Plasmonically enhanced electrochemistry boosted by nonaqueous solvent.

Plasmon excitation of metal electrodes is known to enhance important energy related electrochemical transformations in aqueous media. However, the low solubility of nonpolar gases and molecular reagents involved in many energy conversion reactions limits the number of products formed per unit time in aqueous media. In this Communication, we use linear sweep voltammetry to measure how electrochemical H2O reduction in a nonaqueous solvent, acetonitrile, is enhanced by excitation of a plasmonic electrode. Plasmonically excited electrochemically roughened Au electrodes are found to produce photopotentials as large as 175 mV, which can be harnessed to lower the applied electrical bias required to drive the formation of H2. As the solvent polarity increases, by an increase in the concentration of H2O, the measured photopotential rapidly drops off to ∼50 mV. We propose a mechanism by which an increase in the H2O concentration increasingly stabilizes the photocharged plasmonic electrode, lowering the photopotential available to assist in the electrochemical reaction. Our study demonstrates that solvent polarity is an essential experimental parameter to optimize plasmonic enhancement in electrochemistry. [ABSTRACT FROM AUTHOR]