Performance and Long-term Durability of Nanostructured Ni Anodes Doped with Transition Metals Prepared by Spray Mist Dryer

Various additives for Ni anodes mixed with scandium stabilized zirconia (ScSZ) prepared by spray mist dryer are examined for SOFCs in order to improve their anodic activity and long-term durability. Among the additives examined, it is found that the addition of Mn was highly effective to improve anode activity and sulfur tolerance. In case 5 mol% Mn was added to Ni, at 800 degrees C and 200 mA/cm(2) for 50% pre-reformed CH4 fuels (S/C = 2.5), the anodic overvoltage was as low as 18 mV and the initial cell voltage drop by 5 ppm H2S was ca. 30 mV, which was less than half of the initial cell voltage drop for undoped Ni-cermet anodes. Mn-oxide reacts with NiO during preparation, while Ni metal nanoparticles will be segregated after reduction and Mn-oxide acts as pinning sites to depress grain growth and agglomeration of Ni particles, leading to lower anodic overvoltage and higher sulfur tolerance. Long-term durability up to 3000 hours has been verified.