In situ electrochemical-X-ray Photoelectron Spectroscopy: Rubidium metal deposition from an ionic liquid in competition with solvent breakdown

The electrodeposition of rubidium from an ionic liquid (IL) N-butyl-N-methylpyrrolidium bis(trifluoromethylsulfonyl)imide ([C4mpyrr][NTf2]) has been performed and monitored at a Nickel mesh electrode by using in situ electrochemical-X-ray Photoelectron Spectroscopy (XPS) measurements. At extremely high current values during the deposition of the metal, the solvent breakdown was also observed. By choosing suitable low current values, electrodeposition of Rb can be promoted over the IL degradation. IL degradation was characterised by carbonisation of the electrode-IL-vacuum interface, with the loss of fluorine being relatively pronounced, consistent with reduction of the [NTf2]− anion.