(Invited) Bipolar Membrane Electrolysis for CO2 to Ethylene

Abstract

Carbon dioxide conversion systems are important to drive down the cost of carbon capture through the creation of valuable products. However, how to integrate carbon capture with carbon conversion devices is not yet clear. Bipolar membrane electrolyzers have attracted significant interest as a device which is compatible with carbon capture, as these systems can operate with bicarbonate and carbonate-based solutions. In a bipolar membrane electrolyzer, carbonate is converted to carbon dioxide through a pH swing process driven by water dissociation within the bipolar membrane. However, balancing the rate of water dissociation, carbon dioxide production, and carbon dioxide electrocatalysis remains a critical challenge. Furthermore, steering carbon dioxide electrocatalysis toward a specific high value product such as ethylene is unclear.Here, we set out to examine the activity of Cu, Ag and CuAg catalyst in a carbonate electrolysis system. Cu is a unique metal catalyst and has previously shown the capacity to generate multi-carbon products such as C2H4 and C2H5OH within gas phase anion exchange membrane electrochemical cell. Cu-based catalysts are however known to suffer sluggish C–C coupling kinetics which is a requirement for C2+ product formation. To overcome this challenge, bimetallic are used. For instance, through introducing a known CO-producing catalyst such as Au and Ag with Cu one can perform a cascade reaction. This tandem strategy can enhance performance of multi-carbon products by increasing the coverage of *CO intermediates, known as an important intermediate for C–C coupling, on the Cu surface. Thus, here we will detail a set of experiments aimed at discerning the selectivity of a bipolar-membrane electrode assembly cell which contains Cu, Ag, and Cu-Ag bimetallic electrocatalyst. We examine the impact of temperature, catalyst loading, and system operations. We also will briefly discuss technoeconomic considerations.