Simultaneous Characterizations of Segmented Electrochemical Characteristics and Temperature Distribution in the Hythane-Fueled Direct Internal Reforming Solid Oxide Fuel Cell

The solid oxide fuel cell with direct internal reforming is promising for cost-effective utilization of hythane produced by blending hydrogen in natural gas. Deep understanding of the inhomogeneous distributions of physiochemical processes is essential to assist in optimization of hythane-fueled fuel cell. In this work, the effects of H2 blending ratio and steam-to-carbon ratio on local electrochemical performance and temperature of a segmented cell are comprehensively examined. Local electrochemical processes are clarified by various elec-trochemical impedance spectroscopy investigation approaches including analysis of differences in impedance spectra, distribution of relaxation times, and equivalent circuit model fitting. H2 blending reduces the concen-tration overpotential significantly while also homogenizing the reforming distribution and promoting the anodic electrochemical process in all segments. H2 blending ratio above 20 % greatly reduces the cold spots induced by endothermic reforming but results in hot spots in the gas outlet when the voltage is below 0.7 V because of high electrochemical reaction heat. Regardless of the H2 blending or steam-to-carbon ratio, a nearly thermal neutral state is observed at current density of 300 mA cm-2. These findings demonstrate the potential of boosting performance and simultaneously maintaining homogeneous temperature in the direct internal reforming solid oxide fuel cells.