De/hydrogenation kinetics against air exposure and microstructure evolution during hydrogen absorption/desorption of Mg-Ni-Ce alloys

Lishuai Xie, Jinshan Li, Tiebang Zhang and Hongchao Kou

Renewable Energy, 2017, vol. 113, issue C, 1399-1407

Abstract: Aiming at elucidating the positive effects of Ce element on the oxidation resistance of Mg-based hydrogen storage alloys, Mg-Ni-Ce alloys with different Ce contents have been prepared in a resistance furnace with furnace cooling. The mass fraction of Mg in each sample is 80% to maintain high and consistent hydrogen storage capacity. An 18R-type long-period stacking ordered phase (LPSO) is observed within the Mg12Ce matrix in Mg-Ni-Ce alloys. A two-step activation process is observed in Ce containing alloys. Detailed microstructural characterization of activated samples during air exposure and in-depth analysis of absorption/desorption kinetics on air-exposed samples based on Johnson-Mehl-Avrami (JMA) model are performed to discuss the mechanism underlying improved anti-oxidation properties. CeH2.73 forms after activation and transforms to CeO2 during air exposure, which is earlier and faster than the MgO formation during initial air contact preventing forming a compact and uniform MgO layer on the surface. The formed CeH2.73/CeO2 particles with average particle size less than 60 nm act as catalysts accelerating the hydrogen dissociation and nucleation sites for the MgH2 formation during hydrogenation. After de-/hydrogenation cycles, CeO2 turns back to CeH2.73, which can react with oxygen again when the sample is exposed to air.

Keywords: Mg alloy; Hydrogen storage; Nucleation and growth; Oxidation resistance; Ceria (search for similar items in EconPapers)
Date: 2017
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Citations: View citations in EconPapers (6)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:113:y:2017:i:c:p:1399-1407

DOI: 10.1016/j.renene.2017.06.102

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