Carbon deposition behavior from CH4 fuel on Ni-SCSZ cermet anode in high temprature SOFC

Within 800-1000°C, carbon deposition tends to decrease with increasing temperature on Ni-ScSZ cermet anodes at S/C =0.03 during anodic oxidation of methane. This is supposed to occur under much higher S/C ratio (e.g., =1) according to traditionally accepted thermodynamic equilibrium analysis based on bulk atmosphere S/C. But an opposite trend was observed on Ni-YSZ under the same conditions. Accordingly, a steam reforming local equilibrium model is proposed based on fast equilibrium of H 2 O adsorption on electrode surface and an assumption that, the reforming equilibrium is built up on the basis of local S/C on electrode surface where adsorbed H 2 O determines the steam content for local S/C. The observed different trend between Ni cermets is explained by their different H 2 O adsorption properties. An inhibition effect of current on carbon deposition is explained by the shift in H 2 O adsorption equilibrium induced by anodic reaction major product, H 2 O.