Correlation between kinetics and chemical bonding state of catalyst surface in catalyzed magnesium hydride |
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| Authors: | Tao MaShigehito Isobe Eri MoritaYongming Wang Naoyuki HashimotoSomei Ohnuki Toru KimuraTakayuki Ichikawa Yoshitsugu Kojima |
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| Affiliation: | a Graduate School of Engineering, Hokkaido University, N-13, W-8, Sapporo 060-8278, Japan
b Institute for Advanced Materials Research, Hiroshima University, Japan |
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| Abstract: | We reported on the hydrogen desorption properties, microstructure, kinetics, and chemical bonding state of catalyst surface for composites of MgH2 and 1 mol% Nb2O5 ball-milled for 0.02 h, 0.2 h, 2 h, 20 h under 1 MPa H2 atmosphere, as well as hand-mixed (HM) one. Hydrogen desorption properties were significantly improved by ball-milling with Nb2O5. Then, we estimated by Kissinger Method the activation energy (Ea) of hydrogen desorption reaction that decreased with the increase of ball-milling time. Especially, Ea of the sample ball-milled for 0.2 h was drastically decreased, compared with that of the sample ball-milled for 0.02 h. TEM observations revealed that the distribution of Nb2O5 in MgH2 was gradually improved during ball-milling. On the other hand, we confirmed by XPS that in the sample ball-milled for 0.2 h, Nb2O5-x phase(s) existed at least on the surface. It can be suggested that these deoxidized Nb2O5-x phases eventually decrease Ea as substantial catalyst rather than Nb2O5 itself. |
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| Keywords: | Hydrogen storage materials MgH2 Oxide catalyst XPS TEM |
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