Proton transfer in SrCeO₃-based oxide with internal reformation under supply of CH₄ and H₂O

Mass and charge transfer in a proton-conducting ceramic with internal reformation under the supply of CH₄ + H₂O was experimentally investigated for application to a fuel detritiation system of a fusion reactor. The oxide used in the present experiment was SrCe _0.95Yb_0.05O_3-a, and the electrodes were composed of Ni-SiO₂ paste and Ni wire mesh. The system was described by CH₄ + H₂O|Ni|SrCe_0.95Yb_0.05O _3-a|NiO|O₂ + H₂O. Plots of the I-V (electric current density versus cell potential) characteristic curve were determined under the conditions of different H₂O/CH₄ concentration ratios and temperatures of 600-800 °C. It was found that the system could work well even without any external CH₄ reformer. Mass-transfer process in/on the porous Ni electrode and in the ceramic electrolyte was experimentally clarified. The distribution of carbon depositions in the porous electrode was also determined with EDX by scanning over entire surface in the scope of SEM. The ratio of CH₄ to H₂ direct decomposition to its steam-reforming reaction was found to be different from location to location in the porous Ni electrode.