Kinetics of methane electrooxidation in pure and composite anodes of La_0.3Y_0.1Sr_0.4TiO_3−δ

The electrochemical characteristics of electrolyte-supported solid oxide fuel cells containing pure perovskite anode of La_0.3Y_0.1Sr_0.4TiO₃−_δ, (LYST_A-) and composite anodes with varying fractions (30 and 50 wt%) of yttria-stabilized zirconia (YSZ), LYST_A- (30)YSZ and LYST_A- (50)YSZ, were studied in humidified methane. The 8 wt% CeO₂ and 4 wt% NiO, denoted as (84), were impregnated into the pure and composite anodes for efficient electrooxidation of methane. The studies were carried out to qualitatively estimate the kinetic parameter, exchange current density (i_o), for methane electrooxidation. Evaluation in a 3-electrode configuration with an asymmetric reference electrode yielded the following activity trend: (84)LYST_A- > (84)LYST_A- (30)YSZ > (84)LYST_A- (50)YSZ in the high-overpotential region, with i_o values of 133.2 ± 32.5, 40.8 ± 16.6, and 47.9 ± 16.3 mA cm⁻² at 900 °C, respectively. The presence of YSZ in the composite anodes leads to decrease in i_o and degrading performance. Impedance studies clubbed with equivalent circuit modeling along with physical characterization were used to account for decreased i_o values in composite anodes. Metal support interactions arising between Ni and CeO₂ are studied using a high-resolution transmission electron microscope. Solid oxide fuel cell (SOFC) studies with (84)LYST_A- anode yielded a maximum power density of 591 mW cm⁻² in hydrogen and 429 mW cm⁻² in methane.