Abstract
There is tremendous potential for both small- and large-scale applications of low-temperature operational ceramic fuel cells (LT-CFCs), which operate between 350 degrees C and 550 degrees C. Unfortunately, the low operating temperature of CFCs was hampered by inadequate oxygen reduction electrocatalysts. In this work, the electrochemical characteristics of a semiconductor heterostructure composite based on WO3-CaFe2O4 deposited over porous Ni-foam are investigated. At low working temperatures of 450-500 degrees C, the developed WO3-CaFe2O4 pasted on porous Ni-foam heterostructure composite cathode exhibits very low area-specific resistance (0.78 omega cm(2)) and high oxygen reduction reaction (ORR) activity. For button-sized SOFCs with H-2 and atmospheric air fuels, we have demonstrated high-power densities of 508 mW cm(-2) running at 550 degrees C, and even potential operation at 450 degrees C, using WO3-CaFe2O4 seeded on porous Ni-foam cathode. Moreover, WO3-CaFe2O4 composite heterostructure with Ni foam paste exhibits very low activation energy compared to both WO3 and CaFe2O4 alone, which supports ORR activity. To comprehend the enhanced ORR electrocatalytic activity of WO3-CaFe2O4 pasted on porous Ni-foam heterostructure composite, several spectroscopic tests including X-ray diffraction (XRD), photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) were used. The findings may also aid in the creation of useful cobalt-free electrocatalysts for LT-SOFCs.