Adsorption of PMMIm(TFSI) and OMIm(BF 4 ) Ionic Liquids at Micro-Mesoporous Carbon Surface within a Very Wide Region of Electrode Potentials

The adsorption of 1-propyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide [PMMIm(TFSI)] and 1-octyl-3-methylimidazolium terafluoroborate [OMIm(BF 4 )] at a micro-mesoporous molybdenum carbide derived carbon (MMP-C(Mo 2 C)) electrode using cyclic voltammetry, electrochemical impedance spectroscopy, and low excitation energy (“soft”) X-ray photoelectron spectroscopy (XPS) techniques has been investigated using a three-electrode system. XPS studies were conducted to collect PMMIm(TFSI) and OMIm(BF 4 ) adsorption characteristics at MMP-C(Mo 2 C) electrode surface polarized electrochemically in situ at various negative and positive electrode potentials. We have compared new information collected with the previously studied MMP-C(Mo 2 C)|1-ethyl-3-methylimidazolium tetrafluoroborate system data. Obtained information shows that the RTILs adsorption strength at the MMP-C(Mo 2 C) electrode surface correlates very strongly on the viscosity of the room-temperature ionic liquids (RTILs) studied. Electrochemical and in situ XPS measurements indicated that the residual water, adsorbed in the micropores of the MMP-C(Mo 2 C) electrode, electroreduced very probably at the electrode potentials more negative than −1.0 V causing partial degradation of the RTILs studied. The low-frequency loops, notable in the electrochemical impedance data measured at the negatively charged MMP-C(Mo 2 C) electrode, formed very probably because of very slow mass transport of the studied large RTILs into the electrode pores.