Activating and stabilizing the surface of anode for high-performing direct-ammonia solid oxide fuel cells
Kang Xu, Feng Zhu, Mingyang Hou, Canan Li, Hua Zhang, Yu Chen
Abstract
Ammonia has been recognized as a promising fuel for solid oxide fuel cells (SOFCs) because of its relatively high hydrogen content and high energy density. However, the effective catalysis of ammonia on the surface of state-of-the-art anode greatly hinders the further development of direct ammonia SOFCs. In this study, we report our findings of surface activating and stabilizing of a Ni-based cermet anode for highly efficient and durable operation on ammonia fuel, achieved by a surface coating of CeO2−δ nanoparticles (NPs). When incorporated into a Ni-yttria-stabilized zirconia (Ni-YSZ) anode-supported single cell, the coatings demonstrate an improved electrochemical reaction activity and stability, achieving a high peak power density of 0.941 W·cm−2 at 700 °C, and a promising stability of ∼ 60 h (degradation rate of 0.127% h−1 at 0.5 A·cm−2), much better than those of cells with a bare anode (∼ 0.673 W·cm−2 and degradation rate of 0.294% h−1 at 0.5 A·cm−2). The catalytic NPs significantly enhance the reaction activity toward the decomposition of ammonia and oxidation of hydrogen, especially at low temperatures (< 700 °C), as confirmed by the detailed distribution of relaxation time (DRT) analyses of the impedance spectra of the cells on NH3 fuel.