Improved self-consistency and oxygen reduction activity of CaFe₂O₄ for protonic ceramic fuel cell by porous NiO-foam support

Considerable efforts have been made in the past several decades to search the cheap metal-oxides electrocatalysts with superior electrical properties including ionic and electronic for electrochemical energy devices. In this work, simple orthorhombic structured CaFe₂O₄ nano-particles were embedded on a porous Ni-foam by spin coating method for the application of air electrode for protonic ceramic fuel cells (PCFCs), which provides high oxygen reduction activity than using traditional processes. CaFe₂O₄ coated Ni-foam cathode shows very small area-specific-resistance (ASR) of ≤0.2 Ωcm²and fuel cell device assembled by CaFe₂O₄ coated Ni-foam cathode over ceramic BaZr₀.₈Y₀.₂O₃ (BZY) electrolyte exhibited a peak power density (PPD) of 612 mW cm⁻² when operating at 500°C. The porous Ni-foam support superficially improves the electrical and gas diffusion capabilities along with ionic transport properties of CaFe₂O₄ by narrowing the bandgap to effectively facilitating small polaron hopping energy of valence electrons. However, various spectroscopic measurements such as electrochemical impedance, X-ray photoelectron, thermogravimetric analysis, and Density Functional Theory (DFT) calculations were employed to understand the improved ORR electrocatalyst function of CaFe₂O₄ with Ni-foam support as three-dimensional heterostructure composite cathode. The results can further help to develop functional cobalt-free electro-catalysts for low temperature-PCFCs and other related applications.