Metal doped activated carbon for hydrogen storage

One of the main limitations for hydrogen employment as fuel in vehicles is the difficulty arising from its storage. The main requirements for an on-board storage device are lightweight, small dimensions, safety, high volumetric and gravimetric efficiency and quick loading and unloading [1]. Among suitable materials, activated carbons (ACs) fulfill many of these requirements well. They have a very high specific surface area, from hundreds to thousands square meters, a microporous structure and a good interaction with H2 and are capable of storing ca. 2 wt% of H2 [2]. The amount of stored H2 can be further increased by doping the ACs with metals [3, 4]. In fact, the affinity of metallic nanoparticles for hydrogen and the spillover phenomenon appreciably increase the storage ability. We report on the storage capacity for H2 by high surface area metal doped and undoped AC (ca. 3000 m2/g) under cryogenic conditions (273K up to 100 bar and 77K up to 20 bar). In particular, we tested both noble (Pt, Pd, Rh) and non noble (Ni, Cu) metals as dopants at different loading (0.5 and 2 wt%), deposing them through conventional impregnation methodology and CVD (Chemical Vapor Deposition) technique. The best results, i.e. ca. 6 wt% H2 stored at 77K, 20 bar, have been achieved with 0.5 wt% Cu/AC. However, this represents only a slight improvement with respect to the results obtained with the undoped AC. The real advantage of metal doping becomes evident for the tests at 273K, where Ni or Cu doping brings about a 5-fold increase of the H2 amount stored at 100 bar. Acknowledgments A. Gallo and V. Dal Santo thank the financial support from Regione Lombardia, project “ACCORDO QUADRO Regione Lombardia e CNR” and Italian Ministry of Education, University and Research, project ‘ItalNanoNet’’. References [1] N. Texier-Mandoki, J. Dentzer, T. Piquero, S. Saadallah, P. David, C. Vix-Guterl, Carbon 42 (2004) 2744. [2] L. Schlapbach, A Zuttel, Nature, 414 (2001) 353. [3] C.I. Contescu, C.M. Brown, Y. Liu, V.V. Bhat, N.C. Gallego, J. Phys. Chem. C, 113 (2009) 5886. [4] J. Hu, Q. Gao, Y. Wu, S. Song, Int. J. Hydrogen En., 32 (2007) 1943.