Electrode reaction properties using a reactant gas addition method in a commercial 100 cm² class solid oxide fuel cell

This work investigates the reaction characteristics of the anode and cathode by overpotential analyses in 100 cm² class planar anode-supported SOFCs. The reactant gas addition (RA) technique was applied to analyse the overpotential, which uses the reactant gas flow rate and partial pressure as parameters due to their variation upon adding a reactant species to an electrode. The anodic overpotential was determined to be made up of mass transfer-induced overpotentials of H₂ and H₂O species. The H₂O species account for the majority of the anodic overpotential at the measured current range i.e., 0–150 mA cm⁻². Thus, the anodic reaction is under an extreme H₂O-induced mass-transfer resistance compared with H₂. The RA method showed that the cathodic overpotential was mainly due to a deficiency of O₂ species in the mass transfer through the gas phase rather than the solid phase. Furthermore, both cathodic and anodic overpotentials depended on gas flow rate and utilisation, indicating a significant gas-phase mass transfer effect.