Carbon deposition influenced by gas concentration in a Ni/YSZ anode of an internal-reforming solid oxide fuel cell using a detector layer inside the anode

Carbon deposition on a nickel-based anode is a major concern when using methane as a fuel in SOFCs. In the current study, the influences of electrochemical reaction related to gas concentration distribution inside the fuel electrode on carbon deposition in the vicinities of an electrolyte and the electrode surface were experimentally investigated. A fabricated two- or three-layer structured anode with a detector layer consisting of 50% Ni and 50% Al2O3 for the two-layer anode or 10% Ni and 90% YSZ for the three-layer anode was used. FE-SEM images of the detector layer in the three-layer structured anode clearly suggest the important roles of electrochemical reactions in suppressing carbon deposition by providing oxygen ions and increasing water concentration inside the anode. In addition, the observed carbon deposition at the Ni/Al2O3 top detector layer of the two-layer structured electrode indicates that the surface of the electrode is more likely to be the location for carbon deposition than the vicinity of the electrolyte. From the results, carbon deposition and no deposition conditions could be disclosed as a function of the amount of H2O supplied in fuel and the amount of oxygen ion produced by electrochemical reaction.