Date of Completion
Brian G. WIllis, Jeffrey R. McCutcheon
Field of Study
Master of Science
Room temperature anion exchange membrane fuel cells perform better when transporting carbonate vice hydroxide ions. Carbonate anions provide long-term membrane stability and improved oxygen reduction reaction (ORR) kinetics at the cathode and hydrogen oxidation kinetics at the anode, while also showing membrane conductivity comparable to hydroxide exchange membranes. Researchers have investigated potential non-platinum catalysts that have physical and electrochemical properties that favor the adsorption of CO2 over H2O, thereby, promoting the direct electrochemical formation of carbonate, which prevents membrane degradation caused by OH- attack. This thesis introduces an in situ pulsed Galvanostatic technique that parallels analytical chemistry’s standard addition method designed to quantitatively elucidate the selectivity of OH- and CO32- anions produced electrochemically at the cathode surface. A selectivity model based on gravimetric results was formulated which measures a catalyst’s preference towards the direct electrochemical formation of carbonate. Gravimetric data was obtained at the anode, which could not delineate whether the formation of carbonate originated either indirectly from the ORR formation of OH- or directly by CO32- production at the cathode. Anion residence time within the electrolyte membrane was the dominant factor in reaching carbonate equilibrium at the anode. The results showed that some CO2 was present throughout the hydrated anion exchange membrane. The elemental characterization of a non-platinum catalyst using XRD, SEM EDS, ATR-FTIR, and XPS was performed. The synthesized catalyst favored CO2 adsorption and was found to be a metal oxide doped calcium silicate hydrate from the tobermorite family of minerals.
Crettol, Gregory L., "Carbonate Production Selectivity in a Room Temperature Carbonate Fuel Cell using Pt/C, Co(II)Pc, and Synthesized Tobermorite as ORR Catalysts" (2013). Master's Theses. 495.
William E. Mustain