Catalytic and electrocatalytic behavior of Ni-based cermet anodes under internal dry reforming of CH4 + CO2 mixtures in SOFCs

A high temperature (700–900 °C) SOFC with yttria stabilized zirconia (YSZ) solid electrolyte was constructed and tested on direct feed of simulated biogas (CH4 + CO2) mixtures. Both catalytic, i.e. open-circuit, and electrocatalytic, i.e. closed-circuit, measurements were carried out. Open-circuit kinetic data showed that the rate of the catalytic reaction of the dry(CO2)-reforming of methane is maximized at about equimolar CO2/CH4 feed ratio for all temperatures studied. Closed-circuit data showed that cell output characteristics (i.e. current and power densities) are also maximized for equimolar CO2/CH4 biogas composition. Power densities up to 51.6 mW/cm2 (at V = 453 mV, i = 114 mA/cm2, T = 875 °C) have been obtained. Long-term operation experiments demonstrated that the constructed biogas fuel cell has very stable behavior for all three different simulated biogas compositions fed, including poor, equimolar and rich methane constitutions.