Development of a Direct Ammonia Fueled Hydrogen Membrane Fuel Cell

Recently, ammonia has attracted a considerable interest as a prospective carbon-free fuel source for fuel cells due to the low cost, ease in liquefaction and transportation at ambient temperatures, and high volumetric energy density. As for SOFCs, some promising performance has been obtained with the use of ammonia. However, only the hydrogen generated from the thermal decomposition of ammonia serves as the fuel. As a result, the anode material is required to be active for the ammonia decomposition as well as the electro-oxidation of hydrogen. Hydrogen membrane fuel cell (HMFC), which was firstly proposed by Ito et al.,¹ consists of an ultrathin proton conducting ceramic electrolyte supported on a dense hydrogen permeable metal anode. The cell facilitates efficient power generation, giving 900 mW cm^-2 at 500°C,¹ since reduced electrolyte thickness can significantly decreases the ohmic loss at lower temperatures. Hence, HMFC is attractive as a direct ammonia fuel cell system at intermediate temperature range, if the ammonia can be electro-oxidized at the surface of hydrogen membrane anodes. In this study, we studied the ammonia-fueled HMFC based on Pd dense anode supports and BaCe_0.8Y_0.2O₃ (BCY) electrolyte thin films. BCY electrolyte thin films of 1.0 mm thickness were deposited on a Pd foil by RF magnetron sputtering. La_0.5Sr_0.5Fe_0.8Co_0.2O₃ (LSCF) cathode was screen-printed on BCY and thus, HMFC was obtained. The direct ammonia-fuelced HMFC clearly gives a stable open circuit voltage (OCV) of about 0.9 V and a maximum peak power density of about 100 mW cm^-2 at 600˚C.