Electrode Characterization in a Flowing Electrolyte Reactor for the Electrochemical Reduction of CO2 to CO

Abstract

The development of an energy efficient carbon dioxide (CO2) electroreduction process could simultaneously curb anthropogenic CO2 emissions and provide a sustainable pathway for the generation of chemicals and fuels. Pursuant to this goal, significant efforts have been devoted to developing novel electrocatalysts that enable selective CO2 reduction, at low overpotentials, to a range of valuable products. Of particular interest is carbon monoxide (CO), a key component of synthesis gas, along with hydrogen, which, through Fischer-Tropsch processing, can be used to generate a range of liquid hydrocarbons. While many metals are capable of forming CO as the primary CO2 reduction product, gold may offer the best combination of activity, selectivity, and stability1,2. In contrast to the concerted efforts on catalyst development, fewer studies3–5 have sought to characterize electrode performance within operating electrolyzers, particularly under operating conditions and in cell configurations that more closely align with practical application. To this end, we seek to develop high performance electrodes for the reduction of CO2 to CO and to quantify performance-limiting factors of those electrodes in a gas-liquid electrochemical flow cell. Drawing from advanced polymer electrolyte fuel cell and electrolyzer designs, we have developed a flowing electrolyte electrochemical reactor with gas phase reactant delivery and a reference electrode directly between the anode and cathode. Serving as an analytical platform, the configuration enables in-situ investigation of electrode performance via a combination of polarization and electrochemical impedance spectroscopy. Specifically, we aim to quantify and mitigate resistive losses (e.g., kinetic, ohmic, mass transport) as a function of electrode preparation, cell configuration, and operating conditions. Developing a better understanding of the electrode performance within an operating cell can inform future catalyst / electrode development campaigns for a range of CO2 reduction systems. 1. Hori, Y., Wakebe, H., Tsukamoto, T. & Koga, O. Electrocatalytic process of CO selectivity in electrochemical reduction of CO2 at metal electrodes in aqueous media. Electrochimica Acta 39, 1833–1839 (1994). 2. Salih, T. et al. Cost Effective and Scalable Synthesis of Supported Au Nanoparticles for the Electroreduction of CO 2 to CO. Sci. Adv. Mater. 9, 888–895 (2017). 3. Wu, J. et al. Electrochemical Reduction of Carbon Dioxide II. Design, Assembly, and Performance of Low Temperature Full Electrochemical Cells. J. Electrochem. Soc. 160, F953–F957 (2013). 4. Kim, B., Hillman, F., Ariyoshi, M., Fujikawa, S. & Kenis, P. J. A. Effects of composition of the micro porous layer and the substrate on performance in the electrochemical reduction of CO2 to CO. J. Power Sources 312, 192–198 (2016). 5. Liu, Z. et al. Electrochemical generation of syngas from water and carbon dioxide at industrially important rates. J. CO2 Util. 15, 50–56 (2016).