Fuel Flexible Solid Oxide Fuel Cells with High Power Density: Potential for Future Hybrid Electric Vehicles

Our research describes the performance of a solid oxide fuel cell (SOFC) fueled by directly feeding either premium gasoline or biodiesel to the anode without using external reforming. The novel component of the fuel cell that enables such operation is the mixed conductivity MoO₂-based anode .This unusual ceramic material exhibits excellent electronic/ionic conductivity, and this behavior is believed to lead to high catalytic activity of MoO₂ towards partial oxidation of various hydrocarbons. In addition, MoO₂ shows high resistance to coke formation, which allows longer and more stable operation. Using this anode with premium gasoline as the fuel, a fuel cell demonstrating a power density > 3.0 W cm^-2 at 0.6 V was successfully fabricated. Over a 24 h period of operation, the open cell voltage remained stable at ~0.9 V. At the cell voltage of 0.6 V, its current density dropped over the first 7 h to a value of ~3.0 A cm^-2, where it stayed for the remaining 17 h of the test with a minor fluctuation. Power density of ~2.0 W cm^-2 at 0.6 V was still measured after 24 h on stream with a continuous feed of gasoline. Scanning electron microscopy (SEM) examination of the anode surface pre- and post-testing showed no evidence of coking, which hints at the reason for the observed stability under the harsh cell operating conditions. The implication of this preliminary study is that an SOFC using a MoO₂-based anode has potential for generating electrical power from both gasoline and biodiesel for future hybrid electric vehicles.