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 H ₂S, 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.