Integrated Ni/Nb2O5 nanocatalytic agent dose for improving the hydrogenation/dehydrogenation kinetics of reacted ball milled MgH2 powders |
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| Affiliation: | 1. Advanced Energy Materials Processing Laboratory, Center for Energy Convergence Research, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea;2. Department of Material Science & Engineering, Korea University, Seoul 136-713, Republic of Korea;1. Nanotechnology Research Division, Centre for Mechanical Technology and Automation, Department of Mechanical Engineering, University of Aveiro, 3810-193 Aveiro, Portugal;2. Department of Ceramic Engineering, University of Aveiro, CICECO, 3810-193 Aveiro, Portugal;3. Department of Physics and Astronomy “Galileo Glalilei”, University of Padova, via Marzolo 8, 35131, Padova, Italy;1. ICMPE/CNRS-UPEC UMR 7182, 2-8 rue Henri Dunant, 94320 Thiais, France;2. Dpto. Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain;3. Department of Physics and Astronomy and CNISM, University of Bologna, Bologna, Italy;1. Department of Materials Science and Engineering, Sharif University of Technology, 14588 Tehran, Iran;2. Institute for Nanoscience and Nanotechnology, Sharif University of Technology, 14588 Tehran, Iran;3. Department of Engineering, Shahid Beheshti University, 1983963113 Tehran, Iran;4. Department of Physics, University of Isfahan, 81744 Isfahan, Iran;5. Faculty of New Sciences and Technologies, University of Tehran, Tehran, Iran;1. Nanoengineering Research Group, Centre for Mechanical Technology and Automation, Department of Mechanical Engineering, University of Aveiro, 3810-193 Aveiro, Portugal;2. Instituto de Soldadura e Qualidade, Taguspark, 2740 - 120 Porto Salvo, Portugal |
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| Abstract: | Reactive ball milling (RBM) technique was employed to synthesize ultrafine powders of MgH2, using high energy ball mill operated at room temperature under 50 bar of a hydrogen gas atmosphere. The MgH2 powders obtained after 200 h of continuous RBM time composed of β and γ phases. The powders possessed nanocrystalline characteristics with an average grain of about 10 nm in diameter. The time required for complete hydrogen absorption and desorption measured at 250 °C was 500 s and 2500 s, respectively. In order to improve the hydrogenation/dehydrogenation kinetics of as synthesized MgH2 powders, three different types of nanocatalysts (metallic Ni, Nb2O5 and (Ni)x/(Nb2O5)y) were utilized with different weight percentages and independently ball milled with the MgH2 powders for 50 h under 50 bar of a hydrogen gas atmosphere. The results showed that the prepared nanocomposite MgH2/5Ni/5Nb2O5 powders possessed superior hydrogenation/dehydrogenation characteristics, indexed by low values of activation energy for β-phase (68 kJ/mol) and γ-phase (74 kJ/mol). This nanocomposite system showed excellent hydrogenation/dehydrogenization behavior, indexed by the short time required to uptake (41 s) and release (121 s) of 5 wt% H2 at 250 °C. At this temperature the synthesized nanocomposite powders possessed excellent absorption/desorption cyclability of 180 complete cycles. No serious degradation on the hydrogen storage capacity could be detected and the system exhibited nearly constant absorption and desorption values of +5.46 and ?5.46 wt% H2, respectively. |
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| Keywords: | Reactive ball milling Metal hydrides Nanocomposites Nanocatalysts Gas–solid reaction Cycle-life-time |
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