Methane Pulse and in-Situ Raman Study of Impregnated Ni/CGO As Anodes of SOFC

Abstract

Nickel/gadolinium doped ceria (Ni/CGO) has been a popular SOFC anode material for decades for its superior mix conductivity and excellent oxygen storage capacity. However, the study of Ni/CGO in a realistic working condition is still lacking. Also, not much research has linked the chemical properties of CGO with the carbon resistance which is essential when using hydrocarbon as fuels. In this research, Ni/CGO powder was prepared via impregnation-calcination method. A novel pulse experiment has been conducted on impregnated powder. We did certain pulses of a fixed amount of methane into the sample at 600℃.The outlet gas was monitored by a quadrupole mass spectrometer. The product gas was composed of several species including hydrogen, steam, carbon monoxide, carbon dioxide, and methane that was not participated to the reaction. The major reaction was the partial oxidation of methane. With the increase of pulsing number, the product and shape of product peak changed a lot. Also, we observed a “tail” after each carbon monoxide production peak which was deduced to be the self-oxidation of carbon by the bulk migrated oxygen. After detailed quantitative analysis of the shape and intensity of the peaks and tails. We came up with a model in which the mechanism of methane partial oxidation was confirmed and so was the relation between carbon self-oxidation rate, surface oxygen and bulk oxygen migration rate of CGO. In-situ Raman spectroscopy was performed during the pulse experiment to monitor the change of CGO surface oxygen stoichiometry and deposited carbon. Thus we can confirm the conclusion deduced by pulse experiments and directly relate the carbon self-oxidation rate with bulk oxygen migration of CGO. The results would provide an insight into the design and modification of SOFC anode materials.