Electrodeposition of Au from [EMIm][TFSA] room-temperature ionic liquid: An electrochemical and Surface-Enhanced Raman Spectroscopy study

In this paper we report in situ Surface-Enhanced Raman Scattering (SERS) experiments carried out during the electrochemical deposition of gold from Au(I) cyanocomplexes in the room-temperature ionic liquid (RTIL) 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl) amide ([EMIm][TFSA]). The obtained SERS spectra indicated the co-adsorption of CN− and both anions and cations of the RTIL in the range from −1.8 to +0.3 V vs. an Au quasi-reference electrode (QRE). The surface CN− peak exhibits a Stark tuning of ca. 28 cm−1 V−1. The oxidation of CN− to OCN− was observed at potentials more anodic than 0.3 V. The study was complemented by cyclic voltammetry, pinpointing RTIL reactivity at an Au electrode as well as CN− adsorption effects and Au(I) reduction. SEM observations allowed to identify the conditions for the achievement of continuous Au films as well as the morphological peculiarities of Au electrodeposited from [EMIm][TFSA]. XPS measurements proved that no RTIL is incorporated into the Au film, under the investigated conditions.