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Superior MgH2 Kinetics with MgO Addition: A Tribological Effect
Mire Group, Department of Physics of Materials, Universidad Autonoma de Madrid, Cantoblanco 28049, Madrid, Spain
MERLin group, School of Chemical Engineering, The University of New South Wales, Sydney NSW 2052, Australia
* Author to whom correspondence should be addressed.
Received: 17 July 2012; in revised form: 26 July 2012 / Accepted: 31 July 2012 / Published: 13 August 2012
Abstract: The kinetics of hydrogen absorption/desorption in magnesium can be improved without any catalysis assistance and MgO was found to be more effective than the best catalyst reported so far, i.e., Nb2O5. Herein, a quantitative analysis of the hydrogen kinetics in magnesium modified with MgO was performed in order to identify possible rate controlling mechanisms. While hydrogen absorption was found to be diffusion controlled as commonly reported, hydrogen desorption evolved from nucleation and growth to an interface controlled process depending on the desorption temperature. Comparison with the effect of Nb2O5 indicates that similar rate limiting steps occur regardless of the oxide additive. These findings are reconciled by considering the tribological effect of solid oxide additives, as a correlation between oxides electronegativity and improvement in hydrogen kinetics was found. Such a correlation clearly highlights the mechanical effect of solid oxides in facilitating the grinding and stabilisation of small magnesium particles for efficient and fast hydrogen kinetics.
Keywords: magnesium; hydrogen storage; metal oxides; lubricious oxides; electronegativity; tribology
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Ares-Fernández, J.-R.; Aguey-Zinsou, K.-F. Superior MgH2 Kinetics with MgO Addition: A Tribological Effect. Catalysts 2012, 2, 330-343.
Ares-Fernández J-R, Aguey-Zinsou K-F. Superior MgH2 Kinetics with MgO Addition: A Tribological Effect. Catalysts. 2012; 2(3):330-343.
Ares-Fernández, José-Ramón; Aguey-Zinsou, Kondo-Francois. 2012. "Superior MgH2 Kinetics with MgO Addition: A Tribological Effect." Catalysts 2, no. 3: 330-343.