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

This study reports the catalytic and electrochemical characteristics of La(0.8)Sr(0.2)Cr(0.97)V(0.03)O(3) (LSCV). Catalytic properties of LSCV for the methane steam reforming have been carried out at 800 degreesC. This oxide exhibits a low activity. The most important fact is that no carbon deposit was detected. We have investigated electrochemical behaviour of a LSCV-YSZ composite (YSZ: yttria stabilised zirconia) in H(2)-H(2)O and in CH(4)-H(2)O atmosphere by impedance spectroscopy. Impedance diagrams are composed of two contributions at high-frequency (HF, typically 100 Hz) and at medium-frequency (MF, typically 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 microstructure of the interface of the LSCV-YSZ composite layer and the electrolyte pellet which has to be improved. In CH(4)-H(2)O, an additional semicircle at low-frequency (noted as LF, typically 0.1 Hz) is observed. This LF contribution might be associated with the catalytic rate of the steam reforming of methane reaction. Ruthenium, as a steam reforming catalyst, was added to 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)-H(2)O without ruthenium. Moreover, electrochemical behaviour was stable with time and no carbon deposit was detected after 100 h of operation. These results demonstrated that the gradual methane reforming can be implemented. (C) 2000 Elsevier Science B.V. All rights reserved.