Large oxygen reduction response of CaFe2O4-WO3 heterostructure composite for protonic ceramic fuel cell cathode
Junjiao Li, Naveed Mushtaq, M.A.K. Yousaf Shah, Badriah S. Almutairi, Sajid Rauf, Rizwan Raza, Fenghua Qi, Senlin Yan, Yuzheng Lu
Abstract
Protonic Ceramic fuel cells (PCFCs) hold great promise for many applications; however, their high operating temperature hinders their commercial use in practice. The crucial issue that limits the electrochemical performance of PCFCs (including oxygen and proton-ion-conducting) is the sluggish oxygen redox reaction (ORR) at the cathode surface at low operating temperatures. Herein, we have developed a C aFe 2 O 4 -WO 3 heterostructure composite by interface-vacancy engineered for an efficient ORR electrocatalyst for LT-PCFCs. The C aFe 2 O 4 -WO 3 heterostructure composite exhibits very low cathodic area-specific resistance (ASR) and high oxygen reduction reaction (ORR) activity response at low operating temperatures of 400–550 °C using a BaCe 0.7 Zr 0.2 Y 0.1 O 3-δ (proton-conducting) electrolyte. We have demonstrated high-power density of 585 ± 2% mW-cm −2 with a current density of 1660 mA-cm −2 at 550 °C with H 2 fuel and atmospheric air as oxidant and even with possible operation at 400 °C. Moreover, the CaFe 2 O 4 -WO 3 heterostructure composite shows a very low proton migration energy and activation energy compared to individual CaFe 2 O 4 and WO 3 , helping to promote ORR activity. Various spectroscopic measurements, such as X-ray diffraction, high resolution transmission electron microscopy (HR-TEM), U-visible spectroscopy (UV–visible), Raman spectroscopy , X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations are employed to understand the interfacial properties for the improved ORR electrocatalytic activity of the CaFe 2 O 4 -WO 3 heterostructure composite cathode. Our obtained experimental and theoretical results can further help to develop functional cobalt-free electrocatalysts for LT-PCFCs.