Local and crystal structure of Mg_(1.9)Al_(0.1)Ni hydrogen storage alloys during hydrogen absorption-desorption cycling

摘要

The evolution of crystal structure and chemical state of Mg_(1.9)Al_(0.1)Ni alloy during hydrogen absorption-desorption cycling was examined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). We research the hydrogen storage capacity of the Mg_(1.9)Al_(0.1)Ni by the H/D kinetic curves. The H/D kinetic curves indicate that the hydrogen storage capacity increased with the increased cycles and the samples were activated after 10 cycles have the maximum hydrogen storage capacity. The local structure of Ni atoms was studied by extended X-ray absorption fine structure (EXAFS). The EXAFS results indicate the Ni-Ni bonds distance has no obviously change with the cycles increasing, whereas the Ni-Mg bond lengths increase, and the Ni-Mg bond lengths are longer obviously than before 10 cycles whereas it has no obviously change after 10 cycles.