Hydrogen storage in a rare-earth perovskite-type oxide La0.6Sr0.4Co0.2Fe0.8O3 for battery applications

Recently, rare-earth perovskite-type oxides with the general formula ABO(3) (A rare earth element, B transition metal, O oxygen) are regarded as promising materials for Ni/oxide batteries due to their hydrogen storage ability. In the present study, the hydrogen storage properties of the rare-earth perovskite-type oxide La0.6Sr0.4Co0.2Fe0.8O3 were evaluated in alkaline solution and at various temperatures. The hydrogen storage properties were investigated electrochemically by applying galvanostatic charge/discharge currents. Electrochemical pressure-composition-temperature isotherms were constructed using the Nernst equation. The exchange current density and proton hydrogen diffusion coefficient were calculated using linear polarization measurements and the potential-step method, respectively. Interestingly, the maximum hydrogen absorption capacity, re-calculated from the electrochemical capacity, is 1.72 wt% at 333K and 6molL(-1) KOH. In addition, the hysteresis value, calculated from pressure-composition-temperature isotherms, was 429Jmol(-1) at 333K, while the self-discharge rate was about 25% after 24-h storage at open circuit and at 333K.