Control of carbon deposition over methane-fueled SOFCs through tuning the O/C ratio at the anode/electrolyte interface

Abstract

Direct methane SOFCs can use abundant methane fuel economically and efficiently. Ni-based anode supports are deemed as the best candidate for practical applications owing to their low-cost, chemical compatibility, and high catalytic activity. However, the Ni-based anodes are prone to degradation due to carbon deposition using methane fuel. For the first time, this experimental study, coupling with simulation, discloses the direct causes of carbon deposition are highly depended on the O/C ratio at anode/electrolyte interface, and can be controlled through tuning the mass transfer within anodes, by means of optimizing pore structure of anode-support, methane concentration of input gas, and the operating current density. It is found that more methane transferred to the anode/electrolyte interface can improve power output while resulting in a low O/C ratio at the interface, thus causing carbon deposition. On the contrary, increasing the operating current density and lowering the input methane concentration can reduce the O/C ratio at the interface, thus the carbon deposition over Ni-based anodes can be diminished, and even eliminated. By experimental and numerical analysis, this work points out the O/C ratio is key to the carbon deposition of methane-fueled SOFC, and also provides a facile strategy to mitigate the carbon deposition through tuning anode microstructure and operation parameters such as operating current density, inlet methane concentration.