Enhanced hydrogen oxidation activity and H2S tolerance of Ni-infiltrated ceria solid oxide fuel cell anodes

The effect of Ni infiltration into porous Gd-doped ceria (GDC) anodes on their H2 oxidation performance, with and without added 10 ppm H2S, is reported here. Porous GDC anodes (ca. 10 μm thick) were deposited on yttria stabilized zirconia (YSZ) supports and then infiltrated with catalytic amounts of a Ni nitrate solution, followed by electrochemical testing in a 3-electrode half-cell setup at 500-800 °C. Infiltration of 3 wt.% Ni into the porous GDC anode lowered the polarization resistance by up to 85%, affecting mainly the low frequency impedance arc. When exposed to 10 ppm H2S, the Ni-infiltrated anodes exhibited a ca. 5 times higher tolerance toward sulfur poisoning compared to GDC anodes alone, also showing excellent long-term stability in 10 ppm H2S. In the presence of H2S, it is proposed that Ni, likely distributed as a nanophase, helps to maintain a clean GDC surface at the Ni/GDC interface at which the H2 oxidation reaction takes place. In turn, the GDC will readily supply oxygen anions to the adjacent Ni surfaces, thus helping to remove adsorbed sulfur.