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

The quest for efficient and clean energy sources has led to the exploration of ammonia as a hydrogen carrier due to its high hydrogen content, energy density, and ease of liquefaction. Solid oxide fuel cells (SOFCs) are highly efficient electrochemical devices that can utilize fuels like hydrogen and hydrocarbons. However, the storage and transportation of hydrogen pose significant challenges due to its low bulk density and boiling point. Ammonia-based SOFCs offer a promising alternative, and optimizing their performance at intermediate temperatures is a key area of interest.

A research group of Fulan Zhong and Yu Luo from Fuzhou University focused on the development of pyrochlore La₂Zr_2–xNi_xO_7+δ (LZN_x) oxides as anode catalysts for NH₃-SOFCs. The team investigated the effects of Ni²⁺ doping on the crystal structure, surface morphology, thermal matching with Yttria-stabilized zirconia (YSZ), conductivity, and electrochemical performance of these oxides.

The LZN_x oxides were found to exhibit n-type semiconductor behavior with excellent high-temperature chemical compatibility and thermal matching with the YSZ electrolyte. Additionally, LZN_0.05 demonstrated the smallest conductive band potential and bandgap, leading to a higher power density as anode material for NH₃-SOFCs. The LZN_0.05-40YSZ composite anode achieved a maximum power density of 100.86 mW/cm² at 800 °C, which is 1.8 times greater than that of NiO-based NH₃-SOFCs under identical conditions. Moreover, the LZN_0.05-40YSZ composite anode showed negligible voltage degradation after continuous operation at 800 °C for 100 h, indicating its extended durability.

The development of LZN_x anodes addresses a critical need for efficient anode catalysts in NH₃-SOFCs, offering a significant step forward in the support of the hydrogen economy through ammonia utilization. The improved conductivity and electrochemical performance, coupled with the demonstrated durability, suggest that these materials could play a pivotal role in the future of clean energy generation.