Open- and closed-circuit study of an intermediate temperature SOFC directly fueled with simulated biogas mixtures

An intermediate temperature solid oxide fuel cell (SOFC) based on a gadolinia doped ceria (GDC) solid electrolyte, a Ni(Au)-GDC cermet anode and a La0.54Sr0.46MnO3 perovskite cathode was tested at 600 and 640 °C on direct feed of simulated biogas mixtures. The catalytic (open-circuit) rate of the methane dry (CO2)-reforming reaction over Ni(Au)-GDC anode was found to be maximized at about equimolar CH4/CO2 feed ratio. Cell power density up to 60 mW cm−2, at a cell voltage of 445 mV and a current density of 135 mA cm−2 at 640 °C, has been obtained under closed-circuit cell operation at this optimal feed ratio. Carbon deposition was found not to downgrade cell output characteristics under closed-circuit conditions at constant external loads for ∼120 h, preceded by open- or closed-circuit operation for ∼100 additional hours.