Ammonia-fed reversible protonic ceramic fuel cells with Ru-based catalyst.

The intermediate operating temperatures (~400-600 °C) of reversible protonic ceramic fuel cells (RePCFC) permit the potential use of ammonia as a carbon-neutral high energy density fuel and energy storage medium. Here we show fabrication of anode-supported RePCFC with an ultra-dense (~100%) and thin (4 μm) protonic ceramic electrolyte layer. When coupled to a novel Ru-(BaO) 2 (CaO)(Al 2 O 3 ) (Ru-B2CA) reversible ammonia catalyst, maximum fuel-cell power generation reaches 877 mW cm -2 at 650 °C under ammonia fuel. We report relatively stable operation at 600 °C for up to 1250 h under ammonia fuel. In fuel production mode, ammonia rates exceed 1.2 × 10 -8 NH 3 mol cm -2 s -1 at ambient pressure with H 2 from electrolysis only, and 2.1 × 10 -6  mol NH 3 cm -2 s -1 at 12.5 bar with H 2 from both electrolysis and simulated recycling gas.