Electro-catalytic and Fuel Cell Studies in an Internal Reforming Iso-octane Fed SOFC Using Cu/CeO_2 Composites As Anodic Electrodes

摘要

The internal reforming of iso-octane is examined in a solid oxide fuel cell of the type Cu-CeO_2/YSZ/Pt. The results show that i-C_8H_(18) is efficiently reformed by H_2O to syngas over Cu/CeO_2 composites, free of carbon deposits. Apart from iso-octane reforming, the products distribution at open circuit conditions is also influenced by the associated i-C_8H_(18) thermal cracking and catalytic decomposition reactions as well as by the reverse water gas shift and methanation reactions. At closed circuit operation, the prevailing reactions are related to the electro-oxidation of H_2 and CO and the co-electrolysis of H_2O and CO_2, at anodic and cathodic polarization conditions, respectively. AC impedance spectroscopy studies revealed that the cell and electrode resistances are substantially decreased with increasing temperature leading consequently to higher maximum power densities (12.6 mW/cm~2, 850°C). The diffusion of charged and/or neutral species at the electrode surface is possibly the rate limiting step during fuel cell operation.