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Catalysts 2019, 9(4), 306; https://doi.org/10.3390/catal9040306

Synergistic Effect of New ZrNi5/Nb2O5 Catalytic Agent on Storage Behavior of Nanocrystalline MgH2 Powders

Nanotechnology and Advanced Materials Program, Energy and Building Research, Center, Kuwait Institute for Scientific Research, Safat 13109, Kuwait
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Received: 18 March 2019 / Revised: 25 March 2019 / Accepted: 26 March 2019 / Published: 27 March 2019
(This article belongs to the Section Catalytic Materials)
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Abstract

Due to its availability and high storage capacity, Mg is an ideal material in hydrogen storage applications. In practice, doping Mg/MgH2 with catalyst(s) is necessary in enhancing the de/rehydrogenation kinetics and minimizing both of decomposition temperature and its related apparent activation energy. The present study proposed a new heterogeneous catalytic agent that consisted of intermetallic compound (ZrNi5)/metal oxide (Nb2O5) binary system for using with different concentrations (5−30 wt%) to improve MgH2. Doping MgH2 powders with low concentration (5, 7, 10 wt%) of this new catalytic system led to superior absorption/desorption kinetics, being indexed by the short time that is required to absorb/desorb 4.2−5.6 wt% H2 within 200 s to 300 s. Increasing the doping dose to 15–30 wt% led to better kinetic effect but a significant decrease in the hydrogen storage capacity was seen. The dependent of apparent activation energy and decomposition temperature of MgH2 on the concentration of ZrNi5/Nb2O5 has been investigated. They tended to be linearly decreased with increasing the catalyst concentrations. The results elucidated the crucial role of catalytic additives on the disintegration of MgH2 into ultrafine powders (196 nm to 364 nm diameter). The formation of such nanoparticles enhance the hydrogen diffusion and shorten the time that is required for the hydrogenation/dehydrogenation process. Moreover, this refractory catalytic system acted as a grain growth inhibitor, in which Mg/MgH2 powders maintained their submicron level during the cycle-life-test that was extended to 100 h at 200 °C. View Full-Text
Keywords: Heterogeneous catalysts; hydrogen storage nanomaterials; de/rehydrogenation kinetic; refractory materials; intermetallic compounds; thermal stability; cycle-life-time Heterogeneous catalysts; hydrogen storage nanomaterials; de/rehydrogenation kinetic; refractory materials; intermetallic compounds; thermal stability; cycle-life-time
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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El-Eskandarany, M.S.; Banyan, M.; Al-Ajmi, F. Synergistic Effect of New ZrNi5/Nb2O5 Catalytic Agent on Storage Behavior of Nanocrystalline MgH2 Powders. Catalysts 2019, 9, 306.

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