Hydrogen storage and release of single-Nb-atom doped Al clusters in the gas phase investigated by thermal desorption spectrometry Yufei Zhang and Fumitaka Mafuné Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Japan The increasing energy consumption and the environment minded policy has drawn more attention to the development of clean, efficient and renewable energy source. 1 Hydrogen is a promising energy carrier to replace the carbon-based fossil fuels with advantage of light weight and clean combustion reaction. 2 Therefore, materials such as complex aluminum hydrides and sodium alanates are considered to be an attractive material due to the high hydrogen content. 3 To overcome the high activation barrier of hydrogenation on aluminum clusters, doping of transition metals such as Rh, V, Co and Nb were reported and revealed the importance of charge transfer and geometric effect. 4-7 Recently, doping of single-Nb-atom on aluminum clusters in gas phase was reported to promote hydrogenation of clusters. 8 In the present research, the hydrogenated single-Nb-atom doped Al clusters, Al n NbH p + , in the gas phase were investigated by thermal desorption spectrometry in order to elucidate thermal stability of these clusters, thus reveal the details of hydrogen release such as desorption rate and temperature which are important parameters for hydrogen storage materials. The hydrogenated clusters were produced by laser ablation technique. Mass spectrometric analysis suggested that the niobium doped clusters are more reactive against H 2 compared with aluminum clusters and up to 10 H atoms can be adsorbed on both the cationic and anionic clusters. The thermal desorption spectrometry shows hydrogen desorption started at 550-600 K, and almost all hydrogen released from clusters over 900 K. Thus, continuous desorption of H 2 occurred on small clusters such as Al 4 NbH p + . However, H 2 desorption suddenly occurred on large clusters such as Al 8 NbH p + and almost all H 2 released. The desorption mechanism of Al 8 NbH p + can be explained well in terms of the reported binding energies of H 2 to the cluster. 4 These results indicated that desorption of H 2 from Nb-doped aluminum clusters only occurred at high temperature and remained thermal stability at room temperature. Therefore, it is ideal for hydrogen storage to prevent undesired hydrogen loss. References 1. Basic Research Needs for Electrical Energy Storage—a report of the Basic Energy Sciences Workshop on Electrical Energy Storage, April 2–4, 2007. U.S. Department of Energy Report, July 2007. Graetz, Chem . Soc . Rev ., 2009, 38 , 73–82. 2. Felderhoff, C. Weidenthaler, R. von Helmolt and U. Eberle, Phys . Chem . Chem . Phys ., 2007, 9 , 2643–2653. 3. Jia, J. Vanbuel, P. Ferrari, E. M. Fernández, S. Gewinner, W. Schollkopf, M. T. Nguyen, A. Fielicke, and E. Janssens, J . Phys . Chem . C 2018, 122 , 18247−18255. 4. Nonose, Y. Sone, K. Onodera, S. Sudo and K. Kaya, Chem . Phys . Lett . 1989, 164 , 427−432. 5. Vanbuel, M.-y. Jia, P. Ferrari, S. Gewinner, W. Schollkopf, M. T. Nguyen, A. Fielicke and E. Janssens, Top . Catal ., 2018, 61 ,62–70. 6. Vanbuel, E. M. Fernández, P. Ferrari, S. Gewinner, W. Schçllkopf, L. C. Balbás, A. Fielicke, and E. Janssens, Chem . Eur . J . 2017, 23 , 15638–15643. 7. Ferrari, H. T. Pham, J. Vanbuel, M. T. Nguyen, A. Fielicke and E. Janssens, Chem . Commun ., 2021, 57 , 9518–9521.
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