Alternative anode material for gradual methane reforming in solid oxide fuel cells

This study reports the catalytic and electrochemical characteristics of La0 .8Sr0.2Cr0.97V0.03O3 (LSCV). Catalytic properties of LSCV for the methane s team reforming have been carried out at 800 degreesC. This oxide exhibits a low activity. The most important fact is that no carbon deposit was detect ed. We have investigated electrochemical behaviour of a LSCV-YSZ composite (YSZ: yttria stabilised zirconia) in H-2-H2O and in CH4-H2O atmosphere by i mpedance spectroscopy. Impedance diagrams are composed of two contributions at high-frequency (HF, typically 100 Hz) and at medium-frequency (MF, typi cally 1 Hz). At 800 degreesC, the normalised value of the MF resistance is only three-times higher than that obtained with an optimised Ni-YSZ cermet. In fact, the large difference comes from the HF resistance which is lower for the Ni-YSZ cermet by a factor of 20. This could be explained by the mic rostructure of the interface of the LSCV-YSZ composite layer and the electr olyte pellet which has to be improved. In CH4-H2O, an additional semicircle at low-frequency (noted as LF, typically 0.1 Hz) is observed. This LF cont ribution might be associated with the catalytic rate of the steam reforming of methane reaction. Ruthenium, as a steam reforming catalyst, was added t o the LSCV-YSZ electrode. At 800 degreesC, in pure methane mixed with 5% of steam, this anode material shows similar results to those observed in H-2- H2O without ruthenium. Moreover, electrochemical behaviour was stable with time and no carbon deposit was detected after 100 h of operation. These res ults demonstrated that the gradual methane reforming can be implemented. (C ) 2000 Elsevier Science B.V. All rights reserved.