Improved Ionic Transport Using a Novel Semiconductor Co_0.6Mn_0.4Fe_0.4Al_1.6O₄ and Its Heterostructure with Zinc Oxide for Electrolyte Membrane in LT-CFCs

Abstract

Improving the ionic conductivity and slow oxygen reduction electro-catalytic activity of reactions occurring at low operating temperature would do wonders for the widespread use of low-operating temperature ceramic fuel cells (LT-CFCs; 450–550 °C). In this work, we present a novel semiconductor heterostructure composite made of a spinel-like structure of Co0.6Mn0.4Fe0.4Al1.6O4 (CMFA) and ZnO, which functions as an effective electrolyte membrane for solid oxide fuel cells. For enhanced fuel cell performance at sub-optimal temperatures, the CMFA–ZnO heterostructure composite was developed. We have shown that a button-sized SOFC fueled by H2 and ambient air can provide 835 mW/cm2 of power and 2216 mA/cm2 of current at 550 °C, possibly functioning down to 450 °C. In addition, the oxygen vacancy formation energy and activation energy of the CMFA–ZnO heterostructure composite is lower than those of the individual CMFA and ZnO, facilitating ion transit. The improved ionic conduction of the CMFA–ZnO heterostructure composite was investigated using several transmission and spectroscopic measures, including X-ray diffraction, photoelectron, and UV–visible spectroscopy, and density functional theory (DFT) calculations. These findings suggest that the heterostructure approach is practical for LT-SOFCs.

Keywords

• spinel-structured Co_0.6Mn_0.4Fe_0.4Al_1.6O₄ (CMFA)
• semiconductor ZnO
• CMFA–ZnO heterostructure composite
• higher fuel cell performance
• ionic transport
• LT-SOFC electrolyte