ИСТИНА

The electrochemical reduction of CO2 is currently receiving global interest as one of the most promising solutions to mitigate and utilize CO2 gas, which is regarded as one of the main components of greenhouse gases [1]. The main advantage of using an electrochemical approach for CO2 conversion is that it can be combined with renewable energy resources (solar, wind, hydro) [2]. Efforts have been devoted to develop superior nanostructured electrocatalysts and search appropriate electrolyte solutions. Ionic liquids (ILs) have recently gained significant attention as electrolyte for CO2 reduction due to the following advantages: (i) ILs exhibit a selective and relatively high absorption of CO2; (ii) the solubility of CO2 in ILs can be tuned by tailoring the structures of cations and anions; (iii) ILs decrease the overpotential of CO2 reduction via the complexation of CO2 radical anion with the imidazolium cation [3]. Therefore, ILs are proposed as alternative, more effective next generation solvents for CO2 capture/sequestration and conversion. However, the mass transport of CO2 in ILs is typically slow due to the relatively high viscosity of ILs. One possibility to improve mass transport in ILs is to decrease their viscosity by dilution with water. In this work, we have chosen 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]) as a model IL, to which defined amounts of water are added. Note that [BMIm][BF4] is fully miscible with water. A DOSY-NMR method is used to determine the concentration and diffusion coefficients of CO2 and of other solution components. The effect of water is further explored in the diffusion-controlled CO2 electroreduction in [BMIm][BF4] + water. The diffusion coefficients obtained from DOSY-NMR are compared with those obtained from electrochemical measurements. A silver working electrode is used due to its high selectivity and activity towards the formation of CO. The formation of CO in CO2 electroreduction is confirmed by complementary analysis of products by online gas chromatography. [1] J. Qiao, Y. Liu, F. Hong, J. Zhang, A review of catalysts for the electroreduction of carbon dioxide to produce low-carbon fuels, Chemical Society Reviews, 43 (2014) 631. [2] J. Durst, A. Rudnev, A. Dutta, Y. Fu, J. Herranz, V. Kaliginedi, A. Kuzume, A.A. Permyakova, Y. Paratcha, P. Broekmann, T.J. Schmidt, Electrochemical CO2 Reduction - A Critical View on Fundamentals, Materials and Applications, CHIMIA International Journal for Chemistry, 69 (2015) 769. [3] B.A. Rosen, A. Salehi-Khojin, M.R. Thorson, W. Zhu, D.T. Whipple, P.J.A. Kenis, R.I. Masel, Ionic Liquid–Mediated Selective Conversion of CO2 to CO at Low Overpotentials, Science, 334 (2011) 643.