(513ap) Protocol and Insights for Electrochemical Characterization of Commercial, Carbon-Based Catalyst Supports

Carbon based materials (carbon papers, felts, cloths) are well suited for use in electrochemical applications owing to their high thermal and electrical conductivity, mechanical and chemical stability, and low cost. These materials can be thermally treated to increase their porosity and ECSA and render surface species that aid the deposition of catalytic materials. Measuring the effects of these treatments is necessary for developing a deeper understanding of how these processes influence the performance of the material. This work explores the use of potentiostatic electrochemical impedance spectroscopy (PEIS) along with an RC-ladder network equivalent circuit model developed by Suss et al.[1] for probing commercially available carbon felts at different stages of thermal activation in terms of their electrical resistance, surface area, and the nature of the hierarchical network of pores. Cyclic voltammetry (CV) and inert gas adsorption were also used to verify the results of surface area measurements and scanning electron microscopy was employed to directly observe the hierarchical structure.

Electrocatalysis is a promising method for upgrading CO­­₂ to produce fuels and valuable chemicals. Electrocatalysts used in these processes are often mounted on one of the types of carbon-based substrates mentioned above. Supercritical conditions have been proposed as potential means for increasing reaction rates during CO­₂ electrolysis. Because material stability under anticipated operating conditions is an additional consideration when choosing a substrate, we examined how electrical resistance and surface area of carbon materials changed after repeated exposure to supercritical carbon dioxide. These carbon materials were subjected to cycles of pressurization and heating to achieve a supercritical CO₂ environment followed by venting and cooling to room temperature and pressure. Electrochemical characterization was performed after zero, one, ten, and 100 such cycles.

1. Suss, M.E., et al., Impedance-based study of capacitive porous carbon electrodes with hierarchical and bimodal porosity. 2013. 241: p. 266-273.