The rate and selectivity of methane oxidation over La0.75Sr0.25Cr_xMn_(1-x)O_(3-delta) as a function of lattice oxygen stoichiometry under solid oxide fuel cell anode conditions

摘要

Perovskite-structured La0.75Sr0.25Cr_xMn_(1-x)O_(3-delta) (LSCM,x = 0,0.25,0.50,0.75,and 1) is a potential anode material for direct hydrocarbon solid oxide fuel cells (SOFCs).A pulse reactor system was used to determine the catalytic activity and selectivity of LSCM toward methane total oxidation f between 700 and 900 °C in the absence of gas-phase oxygen.This replicates the SOFC anode environment,in which oxidation occurs through reduction of the oxide lattice.Activity and selectivity were characterized as a function of lattice oxygen stoichiometry,3 - delta.As 3 - delta decreased,the selectivity toward total oxidation decreased for all compositions due to either a change toward partial oxidation or increased dry-reforming activity.The reaction rate and range of oxygen stoichiometry favoring total oxidation increased with increasing Mn content.This was accompanied by a decrease in both carbon formation and oxide stability.These measurements suggest that more-active catalysts are required for SOFC applications.