Effect of polyaniline on hydrogen absorption–desorption properties and discharge capacity of AB3 alloy

A series of AB3/PANI composites were prepared by adding polyaniline (PANI) into La0.7Mg0.25Ti0.05Ni2.975Co0.525 (AB3) hydrogen storage alloy, which was prepared by magnetic levitation melting, and the composites were investigated by XRD and SEM. The effects of PANI concentration on the hydrogen absorption–desorption properties and discharge capacities of AB3 alloy were systematically studied by P–C–T isotherms and LAND battery test system, respectively. The results indicated that the addition of PANI did not change the hydrogen absorption capacity of AB3 alloy distinctly, while the hydrogen desorption plateau pressure of AB3 alloy decreased firstly, and then increased with the increase in the PANI concentration, the minimum plateau pressures of 0.022, 0.1, 0.321 and 0.55 MPa were obtained with PANI concentration of 2 wt% at 25, 50, 80 and 100 °C, respectively. It was theoretically verified by the changes in enthalpy and entropy of AB3/PANI hydrides dehydrogenation which were calculated by Van’t Hoff equation. In the present paper, the phenomenon that PANI improved the hydrogen absorption kinetics of AB3 alloy was found; the influence of PANI concentration on hydrogen absorption kinetics of AB3 alloy was more apparent at higher temperature. The activation energies of dissolved hydrogen in AB3/PANI hydrides were calculated from hydrogen absorption kinetics and the Arrhenius equation. LAND experiments demonstrated that, the AB3/PANI electrodes composites possessed higher cycling discharge capacity retention rates than AB3 electrode alloy.