The Optimization of Anion Exchange Membrane Fuel Cells and Water Electrolyzers by Varying Catalyst Design and Changing Gas Inlet Composition

Researchers around the globe are looking to avoid the consequences of climate change by shifting away from the burning of fossil fuels as a source of energy. While using fossil fuels have negatively affected the earth’s climate for at least the last hundred and fifty years, the introduction of renewables looks to use abundant and naturally occurring resources. Sources of renewable energy include solar power, wind power, hydropower, geothermal energy, and biomass2 . These sources work by converting the abundant source into mechanical, electrical, or chemical energy that can be used to power industrial plants or residential areas and they do so with dramatically less greenhouse gas emissions. Hydrogen is an electricity carrier that can be generated from renewable sources via electrolysis. Hydrogen can also be used by fuel cells or combustion engines to convert the stored chemical energy into electrical or thermal energy. Because of their importance in the hydrogen cycle, both fuel cells and water electrolyzers were investigated in this thesis, with a particular focus on emerging anion exchange membrane fuel cells (AEMFCs) and anion exchange membrane water electrolyzers (AEMWEs). One of the performance-limiting aspects of AEMFC performance is the uptake of CO2 into the cells where it is converted to performance-robbing carbonate and bicarbonate ions. This work fed CO2/O2 mixtures into the cathode of AEMFCs. Steady state voltage plots were developed to see the changes in overpotential due to the charge transfer, ohmic, and area specific resistance contributions to the decrease in performance. AEMWEs can be fed with DI-water or DI-water containing an electrolyte species to enhance the kinetics and conductivity of the cell. Several low-cost NiMo/C electrocatalysts were studied at the AEMWE cathode and their performance compared to Pt/C. The cells tested were broken in on DI-water and then switched to 0.3 M KOH to compare their transient (polarization) and steady-state behavior