Carbon Deposition and Power Density in Rechargeable Direct Carbon Fuel Cells with Gadolinium-doped Ceria and Scandium-stabilized Zirconia

Rechargeable Direct Carbon Fuel Cells (RDCFC) with Ni-cermet anodes and oxide anodes were developed. An RDCFC with a Ni/GDC (gadolinium-doped ceria) anode and 0.3-mm-thick ScSZ (scandium-stabilized zirconia) electrolyte with propane as the charging gas for 5 min at 1173 K exhibited a maximum power density of 258 mW/cm(2), which is a 5 times improvement over a previously reported similar RDCFC except with YSZ electrolyte. To investigate the reaction mechanism in RDCFCs and the role of Ni, the power generation of RDCFCs and conventional SOFCs with Ni/GDC, Ni/ScSZ, GDC, and ScSZ/GDC anodes was evaluated. The results showed that (a) GDC/ScSZ had greater amount of charged carbon than GDC anode, (b) RDCFCs with Ni/ScSZ anode showed extremely poor power generation performance, whereas the SOFC with Ni/ScSZ showed good performance when fueled either by hydrogen or dry methane, (c) carbon deposition by propane did not strongly depend on the presence of Ni under propane charging studied here, and (d) RDCFCs with metal-free anodes, namely, GDC and GDC/ScSZ anodes, exhibited higher power generation performance than did similar SOFCs fueled by dry methane.