Adsorption, Desorption, and Reaction of 1-Octyl-3-methylimidazolium Tetrafluoroborate, [C₈C₁Im][BF₄], Ionic Liquid Multilayers on Cu(111)

Abstract

Multilayers of 1-octyl-3-methylimidazolium tetrafluoroborate [C8C1Im][BF4] have been deposited on a Cu(111) surface by evaporation in UHV. XPS shows that [C8C1Im][BF4] adsorbs without decomposition for substrate temperatures < 300 K. XPS and UPS data indicate that ionic liquid (IL) deposition onto a 120 K Cu(111) surface results in the IL forming multilayers by a simultaneous-multilayer growth process. IL deposition onto a room temperature Cu(111) surface results in a different arrangement where at a coverage of one monolayer the IL forms droplets of about 100 Å height covering only about 1/10th of the surface. Multilayers deposited at 120 K convert to the room temperature arrangement upon heating. Further heating above room temperature causes the IL multilayer droplets to desorb leaving an IL monolayer of ≈6 Å thickness at ≈430 K. At higher temperatures, this monolayer reacts with the surface and BF3 is emitted, leaving products containing C, N, and some F on the surface. We propose a surface reaction where [BF4](-) ions react to form chemisorbed fluorine (Cu-F) and gaseous BF3, with the remaining [C8C1Im](+) decomposing on the Cu(111) in an unidentified manner.

Ionic Liquid Ordering at an Oxide Surface

“…and Villar‐Garcia et al., though we observe a 0.4 eV shift to higher binding energy in all core level spectra, most likely a result of the different methods used to calibrate the binding energy scale (described in S.1). The core‐level spectra and component analysis of the thick film indicate that that [C 4 C 1 Im][BF 4 ] can be deposited intact onto the anatase TiO 2 (101) surface, by evaporation at a temperature of around 220 °C, in agreement with a previous adsorption study on Cu …”

“…They are non‐flammable, non‐volatile and their low symmetry leads to low glass transition temperatures. This means they often exist in the liquid phase at room temperature . This has led to their use in a wide variety of electrochemical systems, including actuators, corrosion inhibitors, energy storage including batteries and supercapacitors, displays and photovoltaic (PV) devices …”

Interactions and stabilisation of acetone, sulfur dioxide and water with 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF4] at low temperatures

“…During desorption the density of highly stabilised states at 61 kJ mol -1 grew for IL coverage between 20 and 35 layers. This was attributed to either the formation of a disordered ionic underlayer at the surface of the IL where the interaction of acetone with the ions would be strongest, or possibly a more general structural change in the IL due to RGJ Interactions and Stabilisations 23/03/2017 24 dissociation of the ion pairs 23 into separate ions, causing a general increase in the number of these highly stabilised sites.…”

“…At 164 K, the ion pairs dissociate into separate ions 23 and can move apart such that each is surrounded by stabilised water molecules. The electric field of the ions is longer range than that of a dipole, so more water at greater distance from the ions can be stabilised.…”

Perspective: Chemical reactions in ionic liquids monitored through the gas (vacuum)/liquid interface

“…[67][68][69][70][71][72] We also exclude studies where the reaction was not carried out in situ, that is, spectra were not recorded while the reaction proceeded, or the sample was moved to a different site in the XPS setup or was even removed from the XPS setup in order to carry out the reaction. [73][74][75][76][77] We also do not address studies that incorporate electrochemical sample manipulation, 66,67,[69][70][71][78][79][80][81][82][83][84][85][86] electrodeposition of metal or organic layers from ILs, [87][88][89][90][91] and IL decomposition 84,[92][93][94][95][96][97][98][99][100][101][102] or nanoparticle formation in ILs. 62,75,103 Each of these topics was studied extensively and would justify a separate review.…”