University of Connecticut OpenCommons@UConn Doctoral Dissertations University of Connecticut Graduate School 5-4-2018 Water and Anion Transport in Electrochemical Devices Travis Omasta University of Connecticut - Storrs,
[email protected] Follow this and additional works at: https://opencommons.uconn.edu/dissertations Recommended Citation Omasta, Travis, "Water and Anion Transport in Electrochemical Devices" (2018). Doctoral Dissertations. 1808. https://opencommons.uconn.edu/dissertations/1808 Water and Anion Transport in Electrochemical Devices Travis John Omasta, Ph.D. University of Connecticut, 2018 In this thesis, the balance and transport of water, hydroxide, and carbonates in Anion Exchange Membrane Fuel Cells (AEMFCs) are investigated. First, macro-scale water is examined, and the need for high membrane conductivity, a predictor of water back diffusion, is demonstrated by operating at lower relative humidities to avoid catalyst layer flooding. Additionally, the distribution of water in the membrane, electrodes, and gas diffusion layers was directly imaged with neutron radiography in an operando fuel cell. The insight from the neutron images was combined with electrode diagnostics evaluating the kinetic, ohmic, and mass transport limitations of the cell, resulting in the ability to also control the micro- scale water through precise engineering of the anode catalyst layer. This understanding ultimately led to the ability reduce the Pt loading significantly, as well as use non-Pt catalysts, while still achieving > 1 W cm-2. Finally, the effects of CO2 and carbonation on AEMFCs was investigated, and the mechanism for carbonate inclusion in the AEM and removal are discussed. It was observed that the carbonation/decarbonation dynamics could allow for the purposeful use of carbonates in electrochemical devices, including current driven electrochemical CO2 separation, which were assembled and their performance characterized.