Understanding\nDirect-Ammonia Protonic Ceramic Fuel\nCells: High-Performance in the Absence of Precious Metal Catalysts

Ammonia has received considerable attention as a promising\ncarbon-free\nhydrogen carrier. At temperatures above 400 °C, NH<sub>3</sub> is thermodynamically unstable with respect to decomposition into\nnitrogen and hydrogen and is, thus, suitable for direct use in solid\noxide fuel cells (SOFCs) without external reforming. However, poor\ncatalytic activity for ammonia decomposition at the moderate temperatures\nof protonic ceramic fuel cell (PCFC) operation has resulted in low\nfuel cell power output relative to operation on hydrogen and likely\ncontributes to reported cell degradation. Here we prepared cells based\non a thermodynamically robust electrolyte, a high activity cathode,\nand an anode with a distinctive structure to overcome challenges of\npoor activity and stability. The cells delivered peak power densities\nof 0.59 and 0.44 W cm<sup>–2</sup> under H<sub>2</sub> and\nNH<sub>3</sub>, respectively, at 500 °C, excellent stability\nover a period of 200 h, and no detectable NO<sub><i>x</i></sub> in the anode exhaust gas.