Effect of methane concentration on reaction behavior in direct-methane solid oxide fuel cells with (Ce,Gd)O2−x-impregnated FeCr layer for fuel processing

A solid oxide fuel cell (SOFC) with a Ni-yttria-stabilized zirconia anode of 1 cm2 area was set up with a porous disk of gadolinia-doped ceria-impregnated FeCr as a gas diffusion layer (GDL) under direct-methane feeding. In this setup of SOFC plus GDL, the tests at 800 °C and ambient pressure show that the current density, the methane conversion rate, the product formation rates, and the CO2 selectivity increased with increasing methane concentration. The major reaction in the GDL is CO2 reforming of methane to produce the syngas (CO plus H2). The anodic electrochemical oxidation of CO from GDL results in an overall rate of CO2 formation being much larger than that of CO formation. There is a synergy between the rate of reaction in the GDL and that over the anode.