Non-Precious Metal-Based Electrocatalytic Cathode Materials for Alkaline Membrane Fuel Cells (AMFC)

Abstract

Proton exchange membrane fuel cells (PEMFC) are a promising power technology for vehicles. However, their commercialization has been hindered due to the cathodic process of the oxygen reduction reaction (ORR). The ORR usually uses high-cost platinum-based electrocatalysts, which is also a major drawback towards commercialization. High overpotential, slow kinetics and irreversibility make the ORR the most challenging hurdle for PEMFC’s. Alkaline membrane fuel cells (AMFC) have emerge as an alternative to PEMFC’s as ORR kinetics are greatly improved in alkaline conditions and allows the use of non-noble metals such as cobalt, manganese and iron. The 3d metal oxide family has attracted the attention of researchers as a result of their low-cost and a robust ORR electrocatalytic activity. Here we present the use of M-doped (M = Mn, Co and Zn) ferrites as ORR electrocatalyst for AMFC applications and study their electrocatalytic mechanism using synchrotron-based X-ray absorption (XAS) techniques. Spinel ferrites were doped with manganese (MnFe2O4), cobalt (CoFe2O4) and zinc (ZnFe2O4) by using the co-precipitation method. X-ray diffraction (XRD) confirmed the formation of the spinel phase. The experimental optimal band gaps observed were 1.86 eV, 1.89 eV and 1.88 eV for MnFe2O4, CoFe2O4 and ZnFe2O4 respectively. ORR electrocatalytic activity was then evaluated in N2-saturated and O2-saturated 1.0 M NaOH using rotary disk electrode (RDE) at 1600 rpm. In situ XAS electrochemical characterization will be carried out in order to investigate at an atomic-level changes occurring to the active sites. Beyond just evaluating the ORR activity of the materials, our work seeks to gain an understanding of the in situ electrocatalytic reactions taking place during ORR. Figure 1