Electrochemical properties of LaMO3 (M=Co or Fe) as the negative electrode in a hydrogen battery Original Research Article

Undoped orthorthombic LaFeO3 and monoclinic LaCoO3 oxides were selected as an anode material for Ni–H battery due to their high electron conductivity by multivalent transition status of B-site cation. Both groups of oxides were prepared by a conventional solid-state reaction method, and their electrochemical charge/discharge properties were investigated. The electrochemical kinetic properties, exchange current density, and proton diffusivity were also extracted using linear polarization measurement and the potential-step method. X-ray photoelectron spectroscopy (XPS) analysis was used to measure the oxidation state of the transition metal in the specimens. A non-linear least-square fitting deconvoluted the peaks, suggesting that the valence state of Fe and Co in the sample was mainly +3. The hydrogen diffusion rate was also estimated using the potential-step method, giving 5.42×10−16 and 5.72×10−16 cm2 s−1 for LaCoO3 and LaFeO3, respectively which are an order of magnitude larger than that of Sr doped LaFeO3 oxide electrodes.