High power-density single-chamber fuel cells operated on methane

Single-chamber solid oxide fuel cells (SC-SOFCs) incorporating thin-film Sm0.15Ce0.85O1.925 (SDC) as the electrolyte, thick Ni + SDC as the (supporting) anode and SDC + BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3−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.