In situ STM investigation of the lithium underpotential deposition on Au(111) in the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide

In the present paper the underpotential deposition (UPD) of lithium on Au(111) from 0.5 mol L-1 LiTFSA in the air-and water stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, [Py-1,Py-4]TFSA, has been investigated by cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM). The pure [Py-1,Py-4]TFSA was found to be inert in the potential regime investigated. The results show that the lithium UPD on Au(111) in [Py-1,Py-4]TFSA begins at potentials considerably positive to the electrode potential of bulk deposition and follows a layer-by-layer mechanism with the formation of at least two monolayers. A large number of monoatomically deep pits appear when the potential reaches positive values, which is an indication that a Li-Au alloy was formed.