Biochar derived from coconut as fuel for the direct carbon solid oxide fuel cell

Coconut char is prepared by pyrolysis and used as the fuel for the direct carbon solid oxide fuel cell (DC-SOFCs), which are composed of yttrium-stabilized zirconia (YSZ) electrolyte and silver and gadolinium-doped ceria (Ag-GDC) cermet electrodes. The microstructure and composition of coconut char are characterized and the performances of DC-SOFCs with coconut char as fuel was investigated. The results show that the as-prepared coconut biochar has a mesoporous structure and a particle size of several microns; moreover, it contains K and Ca elements, favorable for the Boudouard reaction. A peak power density of 255 mW/cm² is observed for the DC-SOFC operated at 800 ℃ with coconut char as fuel; it increases to 274 mW/cm² when the char is loaded with Fe as a promoter to improve the reverse Boudouard reaction. The discharging time of the cell with 0.5 g Fe-loaded coconut char operated at a constant current density of 0.5 A/cm² lasts for 17.6 h, representing a fuel conversion of 39%, demonstrating the feasibility and superiority of coconut char as a fuel for DC-SOFCs.