Modelling and Simulating CO2 Electro-Reduction to Formic Acid Using Microfluidic Electrolytic Cells: The Influence of Bi-Sn Catalyst and 1-Ethyl-3-Methyl Imidazolium Tetra-Fluoroborate Electrolyte on Cell Performance

Authors: Akan C. Offong, E. J. Anthony, Vasilije Manovic

Abstract:

A modified steady-state numerical model is developed for the electrochemical reduction of CO₂ to formic acid. The numerical model achieves a CD (current density) (~60 mA/cm²), FE-faradaic efficiency (~98%) and conversion (~80%) for CO₂ electro-reduction to formic acid in a microfluidic cell. The model integrates charge and species transport, mass conservation, and momentum with electrochemistry. Specifically, the influences of Bi-Sn based nanoparticle catalyst (on the cathode surface) at different mole fractions and 1-ethyl-3-methyl imidazolium tetra-fluoroborate ([EMIM][BF₄]) electrolyte, on CD, FE and CO₂ conversion to formic acid is studied. The reaction is carried out at a constant concentration of electrolyte (85% v/v., [EMIM][BF₄]). Based on the mass transfer characteristics analysis (concentration contours), mole ratio 0.5:0.5 Bi-Sn catalyst displays the highest CO₂ mole consumption in the cathode gas channel. After validating with experimental data (polarisation curves) from literature, extensive simulations reveal performance measure: CD, FE and CO₂ conversion. Increasing the negative cathode potential increases the current densities for both formic acid and H₂ formations. However, H₂ formations are minimal as a result of insufficient hydrogen ions in the ionic liquid electrolyte. Moreover, the limited hydrogen ions have a negative effect on formic acid CD. As CO₂ flow rate increases, CD, FE and CO₂ conversion increases.

Keywords: Carbon dioxide, electro-chemical reduction, microfluidics, ionic liquids, modelling.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.3455699

References:

[1] Laboratory ESR., Division GM. Trends in Atmospheric Carbon Dioxide. Global Greenhouse Gas Reference Network. 2018. p. 1. Available at: https://www.esrl.noaa.gov/gmd/ccgg/trends/ (Accessed: 4 September 2018)
[2] Whipple, D.T., Finke, E.C., and Kenis, P.J. (2010). Microfluidic reactor for the electrochemical reduction of carbon dioxide: the effect of pH. Electrochemical and Solid-State Letters. 2010; 13(9): B109–B111. Available at: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.618.9980&rep=rep1&type=pdf
[3] Wang H., Leung DYC., Xuan J. Modeling of a microfluidic electrochemical cell for CO2 utilization and fuel production. Applied Energy. 2013; Available at: DOI:10.1016/j.apenergy.2012.06.020
[4] Kjeang E., Djilali N., Sinton D. Microfluidic fuel cells: A review. Journal of Power Sources. 2009; Available at: DOI:DOI 10.1016/j.jpowsour.2008.10.011
[5] Bazylak A., Sinton D., Djilali N. Improved fuel utilization in microfluidic fuel cells: A computational study. Journal of Power Sources. 2005; Available at: DOI:10.1016/j.jpowsour.2004.11.029
[6] Chang MH., Chen F., Fang NS. Analysis of membraneless fuel cell using laminar flow in a Y-shaped microchannel. Journal of Power Sources. 2006; Available at: DOI:10.1016/j.jpowsour.2005.11.066
[7] Chen W., Chen F. Theoretical approaches to studying the single and simultaneous reactions in laminar flow-based membraneless fuel cells. Journal of Power Sources. 2006; Available at: DOI:10.1016/j.jpowsour.2006.07.049
[8] Chen F., Chang MH., Hsu CW. Analysis of membraneless microfuel cell using decomposition of hydrogen peroxide in a Y-shaped microchannel. Electrochimica Acta. 2007; Available at: DOI:10.1016/j.electacta.2007.05.072
[9] Li H., Oloman C. Development of a continuous reactor for the electro-reduction of carbon dioxide to formate - Part 2: Scale-up. Journal of Applied Electrochemistry. 2007; Available at: DOI:10.1007/s10800-007-9371-8
[10] Zhang Y., Mawardi A., Pitchumani R. Numerical studies on an air-breathing proton exchange membrane (PEM) fuel cell stack. Journal of Power Sources. Elsevier; 8 November 2007; 173(1): 264–276. Available at: DOI:10.1016/J.JPOWSOUR.2007.05.008 (Accessed: 3 August 2018)
[11] Ahmed DH., Park HB., Sung HJ. Optimum geometrical design for improved fuel utilization in membraneless micro fuel cell. Journal of Power Sources. 2008; Available at: DOI:10.1016/j.jpowsour.2008.06.045
[12] Wang XQ., Xu P., Mujumdar AS., Yap C. Flow and thermal characteristics of offset branching network. International Journal of Thermal Sciences. 2010; Available at: DOI:10.1016/j.ijthermalsci.2009.07.019
[13] Ebrahimi Khabbazi A., Richards AJ., Hoorfar M. Numerical study of the effect of the channel and electrode geometry on the performance of microfluidic fuel cells. Journal of Power Sources. 2010; Available at: DOI:10.1016/j.jpowsour.2010.06.094
[14] Shaegh SAM., Nguyen NT., Chan SH. An air-breathing microfluidic formic acid fuel cell with a porous planar anode: Experimental and numerical investigations. Journal of Micromechanics and Microengineering. 2010; Available at: DOI:10.1088/0960-1317/20/10/105008
[15] Delacourt C., Newman J. Mathematical Modeling of CO2 Reduction to CO in Aqueous Electrolytes. Journal of The Electrochemical Society. 2010; Available at: DOI:10.1149/1.3502533
[16] Xuan J., Leung DYC., Leung MKH., Ni M., Wang H. A computational study of bifunctional oxygen electrode in air-breathing reversible microfluidic fuel cells. International Journal of Hydrogen Energy. 2011; Available at: DOI:10.1016/j.ijhydene.2011.04.151
[17] Wang H., Leung DYC., Xuan J. Modeling of an air cathode for microfluidic fuel cells: Transport and polarization behaviors. International Journal of Hydrogen Energy. 2011; Available at: DOI:10.1016/j.ijhydene.2011.08.033
[18] Krishnamurthy D., Johansson EO., Lee JW., Kjeang E. Computational modeling of microfluidic fuel cells with flow-through porous electrodes. Journal of Power Sources. 2011; Available at: DOI:10.1016/j.jpowsour.2011.08.024
[19] Xuan J. Theoretical Graetz–Damköhler modeling of an airbreathing microfluidic fuel cell. Journal of Power Sources. 2013; 110(231): 1–5.
[20] García-Cuevas RA. Toward geometrical design improvement of membraneless fuel cells: Numerical study. International Journal of Hydrogen Energy. 2013; 38(34): 14791–14800.
[21] Zhang, B., Ye, D. D., Sui, P. C., Djilali, N., & Zhu X. Computational modeling of air-breathing microfluidic fuel cells with flow-over and flow-through anodes. Power Sources. 2014; 259: 15–24.
[22] Yu Y., Zuo Y., Zuo C., Liu X., Liu Z. A hierarchical multiscale model for microfluidic fuel cells with porous electrodes. Electrochimica Acta. 2014; Available at: DOI:10.1016/j.electacta.2013.10.200
[23] Moein-Jahromi M., Movahed S., Kermani MJ. Numerical study of the cathode electrode in the Microfluidic Fuel Cell using agglomerate model. Journal of Power Sources. 2015; Available at: DOI:10.1016/j.jpowsour.2014.12.019
[24] Wu KN., Birgersson E., Kim B., Kenis PJA., Karimi IA. Modeling and Experimental Validation of Electrochemical Reduction of CO2 to CO in a Microfluidic Cell. Journal of the Electrochemical Society. 2015; Available at: DOI:10.1149/2.1021414jes
[25] Jhong HR., Ma SC., Kenis PJA. Electrochemical conversion of CO2 to useful chemicals: current status, remaining challenges, and future opportunities. Current Opinion in Chemical Engineering. 2013; Available at: DOI:10.1016/j.coche.2013.03.005
[26] Lu X., Leung DYC., Wang H., Leung MKH., Xuan J. Electrochemical Reduction of Carbon Dioxide to Formic Acid. ChemElectroChem. 2014; Available at: DOI:10.1002/celc.201300206
[27] Hori Y. Electrochemical CO2 Reduction on Metal Electrodes. Modern Aspects of Electrochemistry. 2008. Available at: DOI:10.1007/978-0-387-49489-0_3
[28] Albo J., Alvarez-Guerra M., Castaño P., Irabien A. Towards the electrochemical conversion of carbon dioxide into methanol. Green Chemistry. 2015; Available at: DOI:10.1039/c4gc02453b
[29] Shamsipur M., Beigi AAM., Teymouri M., Pourmortazavi SM., Irandoust M. Physical and electrochemical properties of ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide. Journal of Molecular Liquids. 2010; Available at: DOI:10.1016/j.molliq.2010.08.005
[30] Galiński, M., Lewandowski, A., & Stępniak I. Ionic liquids as electrolytes. Electrochimica acta. 2006; 51(26): 5567–5580.
[31] Shiflett, M. B., & Yokozeki A. Solubilities and diffusivities of carbon dioxide in ionic liquids:
[bmim]
[PF6] and
[bmim]
[BF4]. Industrial & Engineering Chemistry Research. 2005; 44(12): 4453–4464.
[32] Blanchard L a., Hancu D. Green processing using ionic liquids and CO2. Nature. 1999; Available at: DOI:10.1038/19887
[33] Mihkel K ed. Ionic Liquids in Chemical Analysis: Analytical Chemistry. 1st edn. CRC Press; 2009. p. 448.