A simple, feasible, and non-hazardous laboratory evaluation of direct ammonia solid oxide fuel cells fueled by aqueous ammonia

Direct ammonia solid oxide fuel cells (SOFCs) can generate the carbon-free power with high energy conversion efficiency in the context of Carbon Neutrality, as ammonia is the ideal hydrogen energy carrier with some advantages such as nonflammable, easy to liquefy, mature in storage and transport. Herein, we have developed a simple, feasible, and non-hazardous laboratory evaluation of direct ammonia SOFCs using aqueous ammonia as fuel, taking into account the increasingly stringent safety requirements by China university laboratories. As a result, Ni-based cermet anode-supported single cells with aqueous ammonia (25-28 vol%) can obtain a maximum power density of 644.58 mW/cm(2) at 800 degrees C, which is merely lower than the same cells with hydrogen fuel (795.08 mW/cm(2) at 800 degrees C). Due to limited Ni-based anode catalytic activity for ammonia fuel, electrode polarization impedances a few bigger than the values with hydrogen fuel, and thereby decreasing the cell performance, where the fitting of electrochemical impedances and the distribution of relaxation time (DRT) analysis are employed to better understand the contribution of the different electrode polarization processes with high resolution. Interestingly, to explore the effect of ammonia concentration reduction in ammonia fuel, the cells maintain acceptable electrochemical performance at the front 150 h when operated at a constant voltage of 750 mV, and the obvious concentration polarization and gradual degradation can be observed in the following hundred hours. Our research provides a valuable guidance for a simple, feasible, and non-hazardous laboratory evaluation of direct ammonia SOFCs.