Cu(Pd)-impregnated La0.75Sr0.25Cr0.5Mn0.5O3-δ anodes for direct utilization of methane in SOFC

La0.75Sr0.25Cr0.5Mn0.5O3-delta (LSCM) impregnated with Cu and Cu-Pd was evaluated as SOFC anode for direct utilization of CH4. Impregnation of Cu into porous LSCM anode was found to significantly reduce the anodic overpotential. The lowest overpotential was observed for the LSCM anode impregnated with 20 wt.% Cu. The maximum power density of a single cell with the LSCM+20 wt.% Cu composite anode reached 0.86 and 0.48 W/cm(2) in dry H-2 and CH4 at 850 degrees C, respectively. However, the cell with the LSCM anode appeared to be unstable when exposed to H-2+50 ppm H2S with the power density dropped precipitously in about 2 h. The cell performance was further improved with the impregnation of a small amount of Pd into the LSCM+20 wt.% Cu anode. With the addition of 1.5 wt.% Pd to the anode, the maximum power density at 850 degrees C increased from 0.86 to 0.89 W/cm(2) in H-2 and from 0.48 to 0.6 W/cm(2) in CH4, respectively. The mechanism of methane oxidation on the LSCM and LSCM +Cu anodes is considered to involve direct electrochemical oxidation of methane. However, with Pd dispersed on the LSCM+Cu anode, methane might be firstly catalyzed to form C and H-2 which is followed by oxidation of the cracking products. (c) 2007 Elsevier B.V. All rights reserved.