Triode operation for enhancing the performance of H2S-poisoned SOFCs operated under CH4–H2O mixtures

• Triode SOFCs were operated under CH4–H2O in the presence of H2S.
• Triode operation does not alter the H2S poisoning mechanism of the catalytic sites.
• Triode operation can improve H2S-poisoned anodic electrochemical performances.
• Thermodynamic efficiency close to the unity was achieved.

Performances of Solid Oxide Fuel Cells (SOFCs) were investigated in triode operation mode under methane steam reforming in the presence of H2S. Both the catalytic performances for methane steam reforming and the electrochemical properties for the electrochemical oxidation of hydrogen of a Ni/GDC anode drastically dropped in the presence of 1 ppm H2S. Poisoned catalytic sites are different from those for the hydrogen electrochemical oxidation. Triode operation, i.e. application of moderate negative currents between the anode and an auxiliary electrode, can improve electrochemical properties, as a result of a local production of H2 coming from H2O electrolysis. Some specific triode operations were found to achieve a thermodynamic efficiency close to the unity to avoid any energy overconsumption.