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 electrochemical impedance spectroscopy investigation approaches including analysis of differences in impedance spectra, distribution of relaxation times, and equivalent circuit model fitting. H₂ blending reduces the concentration 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.