High Power Density Single Chamber Fuel Cells Operated on Methane

Single-chamber solid oxide fuel cells (SC-SOFCs) incorporating thin-film Sm_(0.15)Ce_(0.85)O_(1.925) (SDC) as the electrolyte, thick Ni + SDC as the (supporting) anode and SDC + BSCF (Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ)) as the cathode were operated in a mixture of methane, oxygen and helium at furnace temperatures of 500–650 °C. Because of the exothermic nature of the oxidation reactions that occur at the anode, the cell temperature was as much as 150 °C greater than the furnace temperature. Overall, the open circuit voltage was only slightly sensitive to temperature and gas composition, varying from ∼0.70 to ∼0.78 V over the range of conditions explored. In contrast, the power density strongly increased with temperature and broadly peaked at a methane to oxygen ratio of ∼1:1. At a furnace temperature of 650 °C (cell temperature ∼790 °C), a peak power density of 760 mW cm^(−2) was attained using a mixed gas with methane, oxygen and helium flow rates of 87, 80 and 320 mL min^(−1) [STP], respectively. This level of power output is the highest reported in the literature for single chamber fuel cells and reflects the exceptionally high activity of the BSCF cathode for oxygen electro-reduction and its low activity for methane oxidation