Improving Performance and Durability of Low Temperature Direct Ammonia Fuel Cells: Effect of Backpressure and Oxygen Reduction Catalysts

Abstract

Low temperature direct ammonia fuel cells (DAFCs) are attractive for transportation applications. The primary obstacle to their commercial use is their low performance and poor durability. In the present work, we focus on improving DAFCs performance and durability by examining the effect of operating backpressure and oxygen reduction reaction (ORR) catalysts such as Acta 4020, Pd/C and Pt/C. DAFCs with Acta 4020 cathode can reach a peak power density of 390 mW cm−2 which is among the best reported performance, but they can be operated for a period of 11 h at 300 mA cm−2. DAFCs with Pd/C cathode offer a moderate performance with a peak power density of 304 mW cm−2, but has a much improved durability - a continuous operation for up to 36 h with a slow decay rate of ∼1 mV h−1 at 300 mA cm−2. In addition, the degradation pathways for DAFCs with Pd/C cathode are probed by characterizing the initial and final electrodes by XPS, suggesting that cathodic Pd dissolution occurs during the durability test.