All-solid-state direct carbon fuel cells with thin yttrium-stabilized-zirconia electrolyte supported on nickel and iron bimetal-based anodes

• Ni1-xFexOδ-YSZ anode-supported DC-SOFCs are systematically investigated.
• Anode of DC-SOFCs can be reduced in situ by CO generated from Boudouard reaction.
• A proper amount of Fe addition in anode can improve DC-SOFC performance.
• A DC-SOFC with optimal anode of x = 0.1 gives MPD of 529 mW cm−2 at 800 °C.
• DC-SOFC of x = 0.1 run at 0.1 A cm−2 shows a stable plateau of 0.86 V of 15 h.

Solid oxide fuel cells (SOFCs) with thin yttrium-stabilized-zirconia (YSZ) electrolyte supported on composite anode of nickel-iron bimetal and YSZ are prepared and operated directly on Fe-loaded activated carbon fuel, without any liquid medium or purging gas. The composition of the anode is represented as Ni1-xFexOδ (x = 0, 0.05, 0.1, 0.2, 0.3)-YSZ. Experiment result shows that such kind of all-solid-state direct carbon solid oxide fuel cells (DC-SOFCs) perform well at 800 °C, giving maximum output power densities in the range of 425–529 mW cm−2. Similar to the case of a SOFC operated on hydrogen fuel, a small amount of Fe addition into the Ni-based anode can improve the performance of a DC-SOFC and the optimum composition is x = 0.1. A DC-SOFC with Ni0.9Fe0.1Oδ-YSZ anode, loaded with 2.5 g Fe-loaded activated carbon fuel, is steadily operated at a constant current density of 0.1 A cm−2 for 15 h at 800 °C. The anodes and the DC-SOFCs are characterized through XRD, AC impedance spectroscopy, and SEM measurements. The superior performance of the Fe-added anode is analyzed accordingly.