Selective oxidation of methane in an SOFC-type reactor: effect of applied potential

The effect of applied potential on the selective oxidation of methane in a solid oxide fuel cell (SOFC)-type reactor was investigated. A tube-type YSZ was used as an electrolyte where a La1.8Al0.2O3 anode and a conventional La0.85Sr0.15MnO3 cathode were deposited on the inner and outer surfaces of the tube, respectively. The fuel cell-type temperature-programmed desorption (FC-TPD) measurements revealed that the amount of adsorbed oxygen on the anode catalyst was altered with the applied potential. Increasing the applied potential increased the amount of weakly adsorbed oxygen at the "oxygenate site". Two operating modes of the SOFC-type reactor were carried out. In the normal mode, it was found that the rate Of C-2 formation was not affected by an applied potential. The positive potential increased the rate of carbon oxides formation, especially the product CO, while the negative potential suppressed the rates of CO and CO2 formation. For the mixed-flow mode, even though the electrochemically promoted rates did not show significant improvement over the open-circuit rates, the catalytic activities of the anode catalyst to different products were altered by the applied potential with non-Faradaic manner. The change in the selectivity of the active site gave a new aspect to non-Faradaic electrochemical modification of catalytic activity (NEMCA) phenomena. (C) 2002 Elsevier Science B.V. All rights reserved.