Pyrochlore La2Zr2–xNixO7 anodes for direct ammonia solid oxide fuel cells

Developing efficient anode catalysts for direct ammonia solid oxide fuel cells (NH 3 -SOFCs) under intermediate-temperatures is of great importance, in support of hydrogen economy via ammonia utilization. In the present work, the pyrochlore-type La 2 Zr 2− x Ni x O 7+ δ (LZN x , x = 0, 0.02, 0.05, 0.08, 0.10) oxides were synthesized as potential anode catalysts of NH 3 -SOFCs due to the abundant Frankel defect that contributes to the good conductivity and oxygen ion mobility capacity. The effects of different content of Ni 2+ doping on the crystal structure, surface morphology, thermal matching with YSZ (Yttria-stabilized zirconia), conductivity, and electrochemical performance of pyrochlore oxides were examined using different characterization techniques. The findings indicate that the LZN x oxide behaves as an n-type semiconductor and exhibits an excellent high-temperature chemical compatibility and thermal matching with the YSZ electrolyte. Furthermore, LZN 0.05 exhibits the smallest conductive band potential and bandgap, making it have a higher power density as anode material for NH 3 -SOFCs compared to other anodes. As a result, the maximum power density of the LZN 0.05 -40YSZ composite anode reaches 100.86 mW/cm 2 at 800 °C, which is 1.8 times greater than that of NiO-based NH 3 -SOFCs (56.75 mW/cm 2 ) under identical flow rate and temperature conditions. The extended durability indicates that the NH 3 -SOFCs utilizing the LZN 0.05 -40YSZ composite anode exhibits a negligible voltage degradation following uninterrupted operation at 800 °C for 100 h.