La-based perovskites for autothermal reforming: In-situ electrical conductivity measurements and catalytic study

In this work, La-based perovskites with various stoichiometries were synthesized and tested for Autothermal Reforming (ATR) in the intermediate temperature solid oxide fuel cell technology (IT-SOFC). Three materials were compared, namely La0.5Sr0.5Fe0.8Cu0.2O3-d (LaSrFeCu), La0.3Sr0.7Fe0.7Ti0.3O3-d (LaSrFeTi) and La0.4Sr0.4Ba0.2TiO3+d (LaSrBaTi), where the subscripts indicate the atomic ratio used during the synthesis. In the specific, two wet-chemistry approaches (solution combustion synthesis and chelate complex route) were used to obtain mesoporous La-based perovskites. The physico-chemical properties of the materials were analyzed by complementary techniques. Their semiconductive and redox properties were studied by in situ electrical conductivity measurements as a function of the temperature and, at constant temperature, as a function of the partial pressure of oxygen and of the nature of the gaseous atmosphere flowing over the solid. Then, the perovskites were impregnated with 7 wt% of Ni, characterized and tested for the autothermal reforming of ethanol, model biogas, and methane at 500 and 600 C. Catalytic tests showed a high syngas production (83%) when ethanol was used as fuel at 600 C. Analysis of the carbon deposited under different reaction conditions was also performed, in order to assess the stability of the proposed materials. Ni_LaSrBaTi exhibited almost complete ethanol conversion and high H2 selectivity, together with strong structural/thermal stability and good resistance to coke formation, which make this catalyst a promising candidate as IT-SOFC's pre-layer anode.