Hydrogen storage of ZnO and Mg doped ZnO nanowires

ZnO nanowires without or with Mg doping were produced by thermally oxidizing pure Zn or ( Zn + Mg) powders. X-ray diffraction (XRD) patterns indicated that ZnO nanowires with and without Mg doping were crystalline with wurzite structure. The highest hydrogen uptake capability was 2.79 wt% at room temperature and 860 psi for Mg-doped ZnO nanowires. 70.1% of the stored hydrogen can be released at ambient pressure. 2.57 wt% uptake and 68.3% release were measured for ZnO nanowires. Fourier transform infrared spectroscopy (FTIR) showed the formation of O - H bonds, while temperature programmed desorption (TPD) suggested that chemisorbed hydrogen could be released only at 100 - 250 degrees C. The H-2 absorption mechanism on ZnO is discussed.