Redox Stability of SrNb[sub x]Ti[sub 1−x]O[sub 3]–YSZ for Use in SOFC Anodes

Abstract

The conductive properties of bulk SrnormalNbxnormalTi1−xnormalO3 (SNT) and porous SrnormalNbxnormalTi1−xnormalO3 –yttria-stabilized zirconia (YSZ) composites for x=0.01 , 0.05, and 0.20 have been examined under relevant solid oxide fuel cell (SOFC) operating temperatures and redox cycling conditions. The porous composite conductivities were approximately 1 order of magnitude lower than the corresponding bulk material. In order to obtain reasonable conductivity levels for SOFCs, samples were prereduced at 1400°C in H2 . The conductivity of prereduced samples increased with increasing Nb content when directly measured in humidified H2 ; however, when considering the conductivities measured after redox cycling, there appears to be no benefit to using higher dopant levels. After redox cycling at 800°C , a composite conductivity of 1S∕cm at 800°C in humidified H2 (3% normalH2O ) was achieved for x=0.01 and 0.05 and a composite conductivity of 0.5S∕cm was achieved for x=0.20 . Fuel cell power densities of 415mW∕cm2 at 700°C and 640mW∕cm2 at 800°C were achieved in humidified H2 (3% normalH2O ) with a porous SNT–YSZ anode infiltrated with 1wt% Pd and 3wt% CenormalO2 , a 50μm thick YSZ electrolyte, and an normalLa0.8normalSr0.2normalFeO3 (LSF), LSF–YSZ cathode. The implications of these results for the development of redox-stable anodes are discussed.

Enhanced reducibility and conductivity of Na/K-doped SrTi0.8Nb0.2O3

“…The XRD patterns obtained from the samples sintered in air are also shown in Fig. 2 20 Constraint thermodynamic calculations have shown that the stoichiometric phase is thermodynamically stable at high temperatures even in oxidizing atmospheres due to the release of the lattice oxygen. 16 Therefore, the phase purity may be improved during sintering.…”

H2 and CH4 oxidation on Gd0.2Ce0.8O1.9 infiltrated SrMoO3–yttria-stabilized zirconia anode for solid oxide fuel cells

“…9b show that the R U decreases from 0.56 U cm 2 to 0.41 U cm 2 when switched to dry H 2 . By referring to the literature [37,38] for the ion conductivity of YSZ, the 300 mm YSZ pellet contributes 0.36 U cm 2 at 900 C. By comparison, the presence of 3% H 2 O could incur the oxidation of conductive SrMoO 3 to insulating SrMoO 4 , rendering the increase of R U for GDC infiltrated SrMoO 3 eYSZ anode. Lower partial pressure of hydrogen may also be less efficient in reducing SrMoO 4 to SrMoO 3 .…”

Surface and redox chemistry of Sm0.95Ce0.05Fe1−xNixO3−δ perovskites

“…This feature will need to be further explored for sensor applications because reversibility is one of the key factors for a practicable sensor. Additionally, Sm rich surfaces for this type of material suggest enhancement in sensor behavior because the high coordination of Sm (12) should provide more chances of adsorption for target molecules on surface during sensing process than the other lower coordination atoms in the perovskite [34]. Both fresh and reduced samples have Sm rich surfaces due to surface segregation.…”

“…Perovskites with the ABO 3 structure have demonstrated great promise in a variety of applications, including sensors [1][2][3][4][5][6][7][8], solid oxide fuel cells [9][10][11][12][13][14][15][16][17], and catalysis [18][19][20][21]. In the traditional formulation of ABO 3 perovskites, the A site is usually occupied by lanthanides, alkali metals or alkaline earth metals while the B-site elements are typically first row transition metals [4,22,23].…”