Correlation of Fuel Cell Anode Electrocatalytic and ex situ Catalytic Activity of Perovskites La_0.75Sr_0.25Cr_0.5X_0.5O_3−δ (X = Ti, Mn, Fe, Co)

The performance of a series of perovskite oxides having the mutual chemical formula and structure La 0.75 Sr 0.25 Cr 0.5 X 0.5 O 3−δ (X = Co, Fe, Ti, Mn) as solid oxide fuel cell anode electrocatalysts depends on the nature of the substituent element X. The electrocatalytic activity for methane oxidation in a fuel cell correlates well with ex-situ temperature programmed catalytic conversion of CH 4, X = Co > Mn ∼ Fe > Ti, under temperature programmed reaction conditions in 5% CH 4 /He. The total conductivity of the materials in air decreases X = Co > Fe > Mn > Ti. Within the series of catalysts, the order of maximum fuel cell power density depended on feed: CH 4, X = Fe > Mn > Ti; H 2, X = Fe > Mn > Ti; and 0.5% H 2 S/CH 4, X = Ti > Fe > Mn. The Co-containing catalyst was unstable under reducing conditions. A process is proposed to explain the difference in catalyst order and enhanced activities in H 2 S/CH 4 as fuel compared to CH 4 alone.