Hydrogen desorption kinetics of amorphous Mg0.9Ti0.1Ni1−xPdx(x=0, 0.05, 0.1 and 0.15) electrode alloys
(1. Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China;
2. Graduate School, Chinese Academy of Sciences, Beijing 100049,China;
3. Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China)
2. Graduate School, Chinese Academy of Sciences, Beijing 100049,China;
3. Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China)
Abstract: The amorphous Mg0.9Ti0.1Ni1−xPdx (x=0, 0.05, 0.1, 0.15) hydrogen storage alloys were prepared by mechanical alloying. The hydrogen desorption kinetics of the electrode alloys were studied by potentiostatic discharge experiments and linear polarization measurements. The experimental results show that the three-dimensional diffusion model dominates the hydrogen desorption process of the electrode alloys. The rate constants of hydrogen desorption reaction, which are obtained from a linear fitting of the model equation, increase with temperature. The activation energies of hydrogen desorption were calculated according to the Arrhenius equation. The calculated values were 46.2, 24.29, 33.4 and 34.95 kJ/mol for x=0, 0.05, 0.1 and 0.15 of Mg0.9Ti0.1Ni1−xPdx (x=0, 0.05, 0.1, 0.15) electrode alloys, respectively. The exchange current densities were determined by the linear polarization experiments. The variation of exchange current densities with Pd content in the alloy electrodes agrees with that of activation energies with Pd content.
Key words: hydrogen desorption kinetics; potentiostatic discharge; three-dimensional diffusion; activation energy; hydrogen storage alloys