Process Investigation of a Solid Carbon-Fueled Solid Oxide Fuel Cell Integrated with a CO₂-Permeating Membrane and a Sintering-Resistant Reverse Boudouard Reaction Catalyst

The process of a new type of carbon-air battery based on a solid oxide fuel cell (SOFC) integrated with a CO₂-permeable membrane was investigated systematically. Solid carbon fuel was modified with an excellent reverse Boudouard reaction catalyst, Fe_mO_n (active component)-K₂O (promoter). Al₂O₃ as a sintering inhibitor was also introduced to the catalyst-carbon mixture. Two preparation techniques for catalyst-loaded carbon fuel were tried. One technique was the direct mix of all catalyst components and carbon (method A), and the other technique was the premix of all catalyst components before introducing carbon (method B). The performance of carbon-air batteries with different catalyst-carbon mixing techniques was studied by an I-V polarization test. Both techniques produced a good maximum power density of approximately 300 mW cm^-2 at 850 °C. The sintering of the catalyst at high temperatures was prohibited, for the most part, using an Al₂O₃ support (i.e., method B). The carbon-air battery could operate continuously for 314 min at 750 °C with a specific capacity up to 672 mAh g^-1 (on the basis of the solid carbon loaded into the SOFC) and a high fuel conversion of 98.7%. This work optimized the operation of carbon-air batteries and further demonstrated the feasibility of this new type of electrochemical energy device.