Titanium deposition from ionic liquids - appropriate choice of electrolyte and precursor

In this study titanium isopropoxide was dissolved in 1-butyl-3-methyl-imidazolium bis(trifluoromethyl-sulfonyl)imide (BMITFSI) and further in a custom-made guanidinium-based ionic liquid (N(11)N(11)N(pip)GuaTFSI). Electrochemical investigations were carried out by means of cyclic voltammetry (CV) and the initial stages of metal deposition were followed by in situ scanning tunneling microscopy (STM). For BMITFSI we found one large cathodic reduction peak at a potential of -1.2 V vs. Pt, corresponding to the growth of monoatomic high islands. The obtained deposit was identified as elemental titanium by Auger Electron Spectroscopy (AES). Furthermore, we found a corresponding anodic peak at -0.3 V vs. Pt, which is associated with the dissolution of the islands. This observation leads to the assumption that titanium deposition from the imidazolium-based room-temperature ionic liquid (RTIL) proceeds in a one-step electron transfer. In contrast, for the guanidinium-based RTIL we found several peaks during titanium reduction and oxidation, which indicates a multi-step electron transfer in this alternative electrolyte.