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

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 x 10(-16) and 5.72 x 10(-16) cm(2) s(-1) for LaCoO3 and LaFeO3, respectively which are an order of magnitude larger than that of Sr doped LaFeO3 oxide electrodes. (C) 2012 Elsevier Ltd. All rights reserved.