High performance direct ammonia solid oxide fuel cell

Yttria stabilized zirconia (YSZ) and calcia stabilized zirconia (CaSZ) electrolyte materials were tested in an intermediate temperature fuel cell using ammonia as a fuel. Silver, platinum and a nickel cermet were used as anode materials in an annular and a pellet design. At 800 °C, the nickel cermet achieved ammonia conversions of more than 90%, significantly higher than those obtained with silver and platinum. Direct conversion of ammonia at 800 °C, resulted in a power density of 60 mW cm−2 at a current density of 200 mA cm−2, for a pellet system with a nickel cermet anode, and a silver cathode and employing an 8 mol% YSZ electrolyte (thickness of 400 μm).A direct comparison of the performance of a cell running on either hydrogen or ammonia showed that with ammonia the cell generates slightly higher power densities when using a nickel cermet anode. This phenomenon is explained using the Nernst equation, involving the relevant activities at the electrode surface.A comparison of the different oxide ion conducting systems studied under direct ammonia fuel operation shows the high potential of ammonia.