Stable direct-methane solid oxide fuel cells with calcium-oxide-modified nickel-based anodes operating at reduced temperatures

In this study, some basic oxide additives are introduced into the conventional Ni–Ce0.8Sm0.2O1.9 (SDC) cermet anodes of solid oxide fuel cells (SOFCs) for using methane as the fuel. The effects of incorporating basic oxides on the phase composition, electrical conductivity, microstructure, coking tolerance and catalytic/electrocatalytic activity of the anodes are systematically studied. The basic oxide content and the possible phase reactions in the composite anode have considerable effects on the chemical interactions, electrical conductivities and coking resistances of the cermet anodes. The CaO-modified Ni–SDC anode exhibits higher catalytic performance and/or superior coking tolerance than the Ni–SDC and BaO, SrO, MgO, La2O3-modified Ni–SDC anodes under methane steam reforming conditions. The SOFC with a CaO-modified Ni–SDC anode delivers a much higher power generation than the cells composed of the pristine and BaO-modified Ni–SDC anodes using humidified methane fuel at intermediate temperatures. The improved coking resistance of the CaO-modified Ni–SDC anode results in a more stable voltage in the durability test using methane fuel than the cell with a Ni–SDC anode under the same test conditions. In summary, the CaO-modified Ni–SDC composite is a potential coking-resistant and active anode material for SOFCs that use methane as fuel.