Investigating High Current Densities in Ionic Liquid Mediated Electrolysis of Carbon Dioxide

Abstract

The production of chemical feedstock out of CO2 constitutes a key role in the contemporary field of energy storage. Importantly, CO2 is converted by means of renewable power in a single step via a direct electrocatalytic process affording high efficiencies. Research concerning high Faraday efficiencies combined with high current densities for the carbon monoxide (CO) formation as electrolysis product represents a fast and upcoming topic. Recently, it was demonstrated that ionic liquids promote the CO2 reduction by lowering the overpotential and by simultaneously increasing the selectivity for CO evolution.[1] Only a few reports focus, however, on the performance of ionic liquids at high current densities.[2] In our own work, we probed function-selected ionic liquids in a dynamic flow cell setup including a silver gas diffusion electrode towards high current densities by overcoming CO2 transport limitations. In this context, Faraday efficiencies of the electrolysis products as well as electrode potentials are investigated up to 200 mAcm-2 and compared to an aqueous reference electrolyte. Beyond that, the ionic liquids’ ability to act as an inhibitor for the hydrogen evolution reaction (HER) is evaluated. Our work is rounded off by investigations regarding the electrolytic stability of ionic liquids by employing 1H NMR spectroscopy. We proofed stabilities of over 100 h for the electrolysis process. [1] B. A. Rosen, A. Salehi-Khojin, M. R. Thorson, W. Zhu, D. Whipple, P. J. A. Kenis, R. I. Masel, Science 2011, 334, pp. 643-644 [2] J. Medina-Ramos, J. L. DiMeglio, J. Rosenthal, J. Am. Chem. Soc. 2014, 136, pp. 8361-8367