  Direct carbon fuel cells (DCFCs) are highly efficient power generators fueled
by abundant and cheap solid carbons. However, the limited formation of triple
phase boundaries (TPBs) within fuel electrodes inhibits their performance even
at high temperatures due to the limitation of mass transfer. It also results in
low direct-utilization of the fuel. To address the challenges of low carbon
oxidation activity and low carbon utilization simultaneously, a highly
efficient, 3-D solid-state architected anode has been developed to enhance the
performance of DCFCs below 600C. The cells with the 3-D textile anode,
Gd:CeO2-Li/Na2CO3 composite electrolyte, and Sm0.5Sr0.5CoO3 (SSC) cathode have
demonstrated excellent performance with maximum power densities of 143, 196,
and 325 mW cm-2 at 500, 550, and 600C, respectively. At 500C, the cells could
be operated steadily with a rated power density of ~0.13 W cm-2 at a constant
current density of 0.15 A cm-2 with a carbon utilization over 86%. The
significant improvement of the cell performance at such temperatures attributes
to the high synergistic conduction of the composite electrolyte and the
superior 3-D anode structure which offers more paths for carbon catalytic
oxidation. Our results indicate the feasibility of direct electrochemical
oxidation of solid carbon at 500-600C with a high carbon utilization,
representing a promising strategy to develop 3-D architected electrodes for
fuel cells and other electrochemical devices.
