Superior power density solid oxide fuel cells by enlarging the three-phase boundary region of a NiO–Ce0.8Gd0.2O1.9 composite anode through optimized surface structure

Abstract

In an effort to boost the power densities of solid oxide fuel cells (SOFCs) operating at intermediate temperatures (600-750 °C), novel powder synthesis methods have been studied with the goal of increasing the three-phase boundary region of the anode. Porous anodes composed of Ni and Ce0.8Gd0.2O1.9 (GDC) cermet are commonly studied in SOFCs, but the cell performance is limited by their dependency on the three-phase boundaries at which the electrochemical oxidation reaction takes place. This paper presents a remarkable improvement in the electrochemical performance through a significant enlargement of the three-phase boundary region by an optimization of the surface structure. The strategy starts with the premise that the oxide powder particles in aqueous solution carry a positive or negative electrical charge depending upon the pH of the solution, and the charge can be exploited to attach chelated metal ions to their surface, extending the three-phase boundary region. This modified NiO-GDC composite powder resulted in not only an extension of both electronic and O(2-) ionic conduction pathways, but also a suppression of grain growth in the anode during the process of cell fabrication. As the final outcome, the modified Ni-GDC anode-supported cells show far superior power densities (1.85 W cm(-2) at 750 °C and 0.83 W cm(-2) at 600 °C) in H2 compared to the conventional Ni-GDC anode-supported cells (0.61 W cm(-2) at 750 °C and 0.26 W cm(-2) at 600 °C).