A High-Performance Gas-Fed Direct Ammonia Hydroxide Exchange Membrane Fuel Cell

Recently, ammonia has become more attractive for carbon-neutral transportation. Both aqueous ammonia and gaseous ammonia can be utilized for direct ammonia hydroxide exchange membrane fuel cells (DAFCs). Using aqueous ammonia as feedstock for DAFCs presents significant drawbacks to practical stack operations, including higher ammonia crossover rate, increased probability of cathode flooding, and shunt currents. These drawbacks make gaseous ammonia the ideal feedstock for DAFCs. However, the main obstacle to adopting gas-fed DAFCs is their poor performance. Here, we demonstrate that anode humidity and operating temperature are two key factors impacting the performance of gas-fed DAFCs. For the first time, we also investigated the ammonia oxidation reaction (AOR) kinetics in liquid-base-free media at DAFC relevant temperatures and developed a kinetic model for the AOR under these DAFC applicable conditions. Finally, we constructed a one-dimensional (1-D) porous electrode model, simulated the polarization curves, and determined the sources of performance loss for gas-fed DAFCs.