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Water and Anion Transport in Electrochemical Devices

By Travis Omasta

Abstract

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 \u3e 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

Topics: Anion Exchange Membrane Fuel Cell, Water, Flooding, Neutron Radiography, High Performance, Electrodes, Low PGM, Pt-free, Carbonation, CO2 Seperation
Publisher: OpenCommons@UConn
Year: 2018
OAI identifier: oai:opencommons.uconn.edu:dissertations-8060

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