Investigation of Au electrodeposition from [BMP][TFSA] room-temperature ionic liquid containing K[Au(CN)2] by in situ two-dimensional sum frequency generation spectroscopy

In this paper we report an in situ 2D visible-infrared sum frequency generation (VIS-IR SFG) study of the potentiostatic electrodeposition of gold from a solution containing [Au(CN)2]− in 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ([BMP][TFSA]), a room-temperature ionic-liquid (RTIL). We followed the potential-dependent co-adsorption of BMP+ and CN−, released by reduction of the Au(I) complex, in the range –0.8 to −3.0 V vs. Au QRE. We found that the pyrrolidinium ring of BMP+ reorients as a function of potential value and interaction mode with coadsorbed CN−. The Stark tuning of CN− shows that this pseudohalide can be adsorbed in two different ways, that can be correlated with the presence of Au(I) reduction intermediates at the dynamic electrodeposition interface.