Enhanced activities of nano-CeO2−δ@430L composites by zirconium doping for hydrogen electro-oxidation in solid oxide fuel cells

Ceria–zirconia solid solution nanoparticulates, Ce 1− x Zr x O 2− δ ( x  = 0, 0.2, 0.3, 0.4, 0.6, 0.8 and 1.0), are impregnated into the porous 430L stainless steel scaffolds and evaluated as the anode catalysts for solid oxide fuel cells (SOFCs). Combined analyses of X-ray diffraction and Raman scattering reveal the fluorite cubic ( c ) structure up to x  ≤ 0.3 transforms to a mixture of the cubic and metastable tetragonal ( t ″) phases for 0.4 ≤  x  ≤ 0.8, with the onset of tetragonal distortions at x  = 0.8. Temperature-programmed reduction in H 2 indicates that doping Zr 4+ into the ceria lattice could improve the oxygen storage capacity. Nonetheless, the charge transfer process within the bulk Ce 1− x Zr x O 2− δ or across the interfaces of Ce 1− x Zr x O 2− δ |YSZ becomes increasingly sluggish at x  ≥ 0.3. The two opposite effects yield the smallest anode polarization resistances at x  = 0.3, e.g. , 0.08 ± 0.01 Ω cm 2 for Ce 0.7 Zr 0.3 O 2− δ versus 0.24 ± 0.02 Ω cm 2 for CeO 2− δ or 0.26 ± 0.04 Ω cm 2 for Ce 0.4 Zr 0.6 O 2− δ at 800 °C. Furthermore, thin YSZ electrolyte fuel cells with impregnated La 0.6 Sr 0.4 Fe 0.9 Sc 0.1 O 3− δ – YSZ cathode supports produce peak power densities of 1.24 W cm −2 at 800 °C for nano-Ce 0.7 Zr 0.3 O 2− δ @430L anodes, approximately 80% higher than 0.67–0.70 W cm −2 on nano-CeO 2− δ @430L or nano-Ce 0.4 Zr 0.6 O 2− δ @430L anodes.