CBE Distinguished Lecture: Electrochemical Reduction of CO2: Challenges for Materials and System Design

Abstract: The electrochemical reduction of CO2 holds considerable potential as a means for converting CO2 emitted from stationary sources and ultimately from the atmosphere into fuels and chemicals using renewable energy sources (e.g., wind, solar radiation). The challenge is to select the required materials and to design electrochemical reactors that can accomplish this goal economically. While considerable insight into the effects of catalysts and electrolyte selection have been achieved in laboratory studies using H-cells or flowthrough compression cells, such devices cannot achieve the current densities needed for industrial scale (> 100 mA/cm2). This talk will first review what has been learned from laboratory studies concerning the effects of catalyst composition and structure as well as electrolyte composition on the activity and selectivity of Cu and Ag catalysts for CO2 reduction and the factors affecting product current density. It will then be shown that to meet the demands of industrial-scale operation, it is necessary to consider membrane electrode assemblies (MEAs). The structure of the MEA involves an ionomeric polymer membrane as the electrolyte, coated with an anode catalyst layer (aCL) on one side and a cathode catalyst layer (cCL) on the other side. A hydrated stream of CO2 is supplied to the cCl through a gas diffusion layer and an aqueous stream of electrolyte is supplied on the backside of the aCL. Experimental work has shown that the ionomer membrane and the ionomer in which the catalysts are imbedded must be fully hydrated to maintain high ionic conductivity through these elements to lower the voltage required for a given current density. This presentation will end with an illustration of the challenges that must be met to design an MEA.

Bio: Alexis Bell is currently professor emeritus in the Department of Chemical and Biomolecular Engineering at UC Berkeley and is an affiliate at the Lawrence Berkeley National Laboratory. He received his B.S. and Ph.D. degrees in chemical engineering from the Massachusetts Institute of Technology. His research specialty is catalysis and chemical reaction engineering with an emphasis on understanding the fundamental relationships between catalyst structure and composition and catalyst activity and selectivity. The objectives of his program are pursued through a combination of experimental and theoretical methods, enabling the attainment of a deeper understanding of the core issues of interest than can be achieved by using either approach alone. Bell has published nearly 800 papers for which he has received numerous national and international recognition. Bell is a member of the National Academy of Sciences, the National Academy of Engineering, a member of the American Academy of Arts and Sciences and a foreign member of the Russian Academy of Sciences.

Host: Iryna Zenyuk