Correlation of Fuel Cell Anode Electrocatalytic and ex situ Catalytic Activity of Perovskites La_(0.75)Sr_(0.25)Cr_(0.5)X_(0.5)O_(3-δ) (X = Ti, Mn, Fe, Co)

摘要

The performance of a series of perovskite oxides having themutual 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 electrocatalysls 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 CH4, X = Co > Mn ～ Fe > Ti, under temperature programmed reaction conditions in 5% CH4/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: CH4, X = Fe > Mn > Ti; H2, X = Fe > Mn > Ti; and 0.5% H2S/CH4, 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 H2S/CH4 as fuel compared to CH4 alone.