(690c) NiMo-Ceria-Zirconia Catalytic Reforming Layer for Solid Oxide Fuel Cells Running on Isooctane

Solid oxide fuel cells (SOFCs) are a promising energy conversion device because they can efficiently and directly convert the chemical energy of fuels into electrical energy. Due to the high operating temperatures (typically 600-1000 °C), SOFCs hold particular promise because of their ability to use a variety of complex liquid fuels, such as conventional liquid transportation fuels (e.g., gasoline, diesel-like fuels and jet fuels) and next generation liquid bio-fuels (e.g., biodiesel), either by using external reforming systems or directly feeding these fuels into their inexpensive transition metal-based anodes

Nickel-based anodes are commonly used in SOFCs owing to their low cost, good chemical stability, and excellent catalytic activity toward hydrogen oxidation and reforming of small hydrocarbon molecules. However, the Ni-based anodes are well known for promoting severe surface carbon deposition. Excessive formation of carbon species on the anode leads to a rapid deterioration of the cell performance by physically blocking access of the reactants to the active catalyst sites. To operate the Ni-based SOFCs by feeding liquid isooctane fuel, a catalytic layer can be applied over the Ni-based anode to act as an internal micro-reformer. The micro-reforming layer is designed to convert the mixture of isooctane and air to synthesis gas (hydrogen and carbon monoxide), which is believe to suppress the carbon deposition over the Ni-based anode.

In this work, a NiMo-Ceria-Zirconia (NiMo-CZ) catalyst was used as a micro-reforming layer for SOFCs running on isooctane. The catalyst layer was applied on top of the conventional anode supported single cell with a configuration of Ni-yttira-stabilized zirconia (YSZ) anode, YSZ/Ce_0.8Sm_0.2O_1.9 bi-layer electrolyte and La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ cathode. Our results showed that application of the novel catalyst layer was an effective way to enhance the electrochemical oxidation of complex hydrocarbons at the anode. At 750 °C, the single cell exhibited a low polarization resistance of 1.36 Ω cm² and a good maximum power density of 405 mW cm^-2 in isooctane/air. At the current density of 500 mA cm^-2, the cell voltage presented a fairly low degradation rate of 3.0 mV h^-1 during over 12 h stability test. The excellent electrochemical performance suggests the high catalytic activity of the NiMo-CZ catalyst for reforming isooctane and suppressing performance degradation of the single cell in the isooctane fuel.