Effect of Ce Doping on the Performance and Stability of Strontium Cobalt Ferrite Perovskites as SOFC Anode Catalysts

Abstract

The bulk structure, surface characteristics, catalytic properties, button cell performance, and stability of perovskite-type oxides with the formula Sr 1-x Ce xCo 0.2 Fe 0.8 O 3-d (x = 0.10, 0.15, and 0.20) were investigated as potential anode electro-catalysts for solid oxide fuel cells. In situ X-ray diffraction results indicated that the structural stability of the cerium-doped perovskites was enhanced with increasing cerium concentration. The catalysts with lower cerium concentration transformed from the initial cubic structure to a lower symmetry structure at high temperatures in a reducing environment. All the catalysts, however, were restored to the original cubic structure after re-oxidation. Electronic conductivity tests showed that the cerium-doped samples break down at higher temperatures, but display potential in terms of structural integrity and high conductivity at temperatures lower than 600°C. The new materials showed better performance than Ni-YSZ in catalytic methane oxidation tests. The sulfur tolerance is significantly enhanced with the cerium-doped perovskites, showing no deactivation for up to 10 h of operation under 50 ppm H 2 S. X-ray photoelectron spectroscopy analysis on the poisoned samples suggests that the sulfur may exist on the surface primarily as strontium sulfate. The sample with a cerium loading of 15 % (x = 0.15) showed a particularly high sulfur tolerance during chronoamperometry tests and its button cell performance matched well with that of Ni-YSZ anode. Sr 1-x Ce x Co 0.2 Fe 0.8 O 3-d (x = 0.10, 0.15, and 0.20) samples may have potential for low or intermediate temperature SOFC operation in which sulfur-containing hydrocarbon fuels are used, although they would not be stable at higher temperatures.

Reduction of operation temperature in SOFCs utilizing perovskites: Review

“…Choi et al [56] investigated the effect of doping Ce in Sr1-xCexCo0.2Fe0.8O3-δ (x = 0.10, 0.15, and 0.20) samples prepared by EDTA-citrate complexing approach and they stated that the higher Ce doping in A-site could lead to more stable perovskites. In addition, the samples showed excellent Sun et al [51] evaluated Mo doped Pr0.5Ba0.5MnO3δ (Mo-PBMO) double perovskite material synthesized by modified sol-gel approach as anode material for solid oxide fuel cell.…”

A cobalt-free electrode material La0.5Sr0.5Fe0.8Cu0.2O3−δ for symmetrical solid oxide fuel cells

“…Cobalt-iron based typical cathode materials with single phase were then used as SSOFC electrodes, for example, Ln x Sr 1-x Co 0.8 Fe 0.2 O 3-δ (Ln = La, Ce) [12][13][14] and SrFe 0.75 M 0.25 O 3-δ (M = Ti, Zr, V, Nb, Cr, Mo and W) [15]. Although these materials demonstrate considerable activity for hydrogen or methane oxidation, their structure stability in reducing atmospheres is still a significant concern [16].…”

Sucrose-Assisted Solution Combustion Synthesis of Doped Strontium Ferrate Perovskite-Type Electrocatalysts: Primary Role of the Secondary Fuel

“…Otherwise, when cobalt replaces iron in the B-site of SrFeO 3-δ , the electronic conductivity improves, thanks to the intrinsic property of Co, as well as the ionic conductivity [49]. In addition, by introducing Cobalt as dopant, the lattice constant gradually decreases, limiting the distortion of the cubic structure [50]. Cobalt-containing cathodes are known for their good electrochemical performances at low-intermediate operating temperatures (20-700 • C) because of their excellent activity in the oxygen reduction reaction [38,[51][52][53].…”