(Invited) Experimental Measurement of Spatial Activity on CO2 & CO Reduction Gas Diffusion Electrodes

Abstract

Over the past decade, the accessible current densities of electrochemical CO2 reduction (CO2R) and CO reduction (COR) systems have increased by orders of magnitude, following the adaptation of the Gas Diffusion Electrode (GDE) architecture. As GDEs increase in size from cm2 to m2, cell stability and performance can change due to physical and chemical spatial variations within the cell, which can be exacerbated by the chemical complexity of carbonaceous electrochemical systems. Here, we present two approaches to measuring spatial activity: testing iteratively larger electrodes and harmonizing those results with a multi-port sampling reactor capable of measuring product concentration along the length of the reactor. This dual-pronged approach allows for benchmarking of electrochemical performance and selectivity down the channel as reaction conditions vary. We examine selectivity changes through the lens of fundamental electrochemical properties and provide subsequent recommendations for device operation as devices approach > kW scale. Experimental results are aligned with a 2-D (path length and electrode thickness) transport model to compare physical simulations with measured electrochemical signatures. Feedback loops between experiment and simulation were developed to incorporate cell inhomogeneities into the transport model. We identify potential causes for poor catalyst utilization in large electrodes for both COR and CO2R and provide recommendations for translating bench-top scale results to pilot scale results.