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Catalytic effect of titanium nitride nanopowder on hydrogen desorption properties of NaAlH4 and its stability in NaAlH4 |
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| Authors: | Ji Woo Kim,Jae-Hyeok Shim,Seul Cham Kim,Andreas Borgschulte,Robin Gremaud,Andreas Zü ttel,Kyu Hwan Oh |
| Affiliation: | a Department of Materials Science and Engineering, Seoul National University, Seoul 151-742, Republic of Korea b Materials Science and Technology Research Division, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea c Division of Hydrogen and Energy, Department of Environment, Energy and Mobility, Empa Materials Science and Technology, CH-8600 Dübendorf, Switzerland |
| Abstract: | Single crystalline titanium nitride (TiN) nanopowder is synthesized by a mechano-chemical reaction between titanium chloride (TiCl3) and lithium nitride (Li3N) by means of high-energy ball milling. The TiN nanopowder has an average particle size of 6 nm and is introduced into sodium alanate (NaAlH4) as a catalyst. During hydrogen sorption cycles, TiN-catalyzed NaAlH4 exhibits a greater hydrogen desorption rate and higher hydrogen capacity than TiCl3-catalyzed NaAlH4. Contradicting thermodynamic predictions, in situ X-ray diffraction results reveal that TiN nanopowder remains stable and produces no by-products (e.g., Ti-Al compounds) in the reaction with NaAlH4 during hydrogen desorption. In situ Raman spectroscopy also confirms the stability of TiN nanopowder in NaAlH4. This implies that the sustained hydrogen sorption kinetics and hydrogen capacity of TiN-catalyzed NaAlH4 originate from the structural and chemical stability of TiN nanopowder in NaAlH4 for the given conditions of the hydrogen cycle test. |
| Keywords: | Hydrogen storage Sodium alanate Catalyst Titanium nitride nanopowder In situ X-ray diffraction In situ Raman spectroscopy |
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