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 Title: VIBRATIONAL SUM FREQUENCY STUDY OF THE INFLUENCE OF WATER-IONIC LIQUID MIXTURES IN THE CO2 ELECTROREDUCTION ON SILVER ELECTRODES Author(s): Garcia Rey, Natalia Contributor(s): Dlott, Dana Subject(s): Spectroscopy as an analytical tool Abstract: Understand the molecular dynamics on buried electrodes under electrochemical transformations is of significant interest. There is a big gap of knowledge in the CO$_{2}$ electroreduction mechanism due to the limitations to access and probe the liquid-metal interfaces [1,2]. Vibrational Sum Frequency Spectroscopy (VSFS) is a non-invasive and surface sensitive technique, with molecular level detection that can be used to probe electrochemical reactions occurring on the electrolyte-electrode interface [2]. We observed the CO$_{2}$ electroreduction to CO in ionic liquids (ILs) on poly Ag using VSFS synchronized with cyclic voltammetry. In order to follow the CO$_{2}$ reaction in situ on the ionic liquid-Ag interface; the CO, CO$_{2}$ and imidazolium vibrational modes (resonant SFS) were monitored as a function of potential. We identified at which potential the CO was produced and how the EMIM-BF$_{4}$ played an important role in the electron transfer to the CO$_{2}$, lowering the CO$_{2}^{-}$ energy barrier. A new approach to reveal the double layer dynamics to the electrostatic environment is presented by the study of the nonresonant sum frequency intensity as a function of the applied potential. By this method, we studied the influence of water-ionic liquid mixtures in the CO$_{2}$ electroreduction on Ag electrode. We observed a shift to lower potentials in the CO$_{2}$ electroreduction in water-ILs electrolyte. Previous studies in gas diffusion fuel cells have shown the CO$_{2}$ electroreduction in a water-imidazolium�based ILs on Ag nanoparticles at lower overpotential [3]. Our VSFS study helps to understand the fundamental electrochemical mechanism, showing how the ILs structural transition influences the CO$_{2}$ electroreduction. [1] Polyansky, D. E.; Electroreduction of Carbon Dioxide, 2014, Encyclopedia of Applied Electrochemistry, Springer New York, pag 431-437. [2] Bain, C. D.; J. Chem. Soc., Faraday Trans., 1995, 91, 1281. [3] Rosen, B. A. et al; Science, 2011, 334 (6056), 643. Rosen, B. A. et al.; J. electrochem. Soc., 2013, 160 (2), H138. Issue Date: 26-Jun-15 Publisher: International Symposium on Molecular Spectroscopy Citation Info: ACS Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/79343 Date Available in IDEALS: 2016-01-05
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