EXPLORE THE HYDROGENATION AND DEHYDROGENATION PROCESSES OF MG NANOSTRUCTURES FOR HYDROGEN STORAGE

Yiping Zhao

Department of Physics and Astronomy, University of Georgia , Athens , GA 30602 , USA

On-board Hydrogen storage is the bottleneck for vehicle application s . In order to achieve the FreedomCar targets in 2010 proposed by DOE, the gravimetric hydrogen density should be ~ 6 mass%, and be able to be operated at ambient conditions (< 373 K and 2 atm). It has been demonstrated that the safest way to store hydrogen is solid state material. Currently, there are three types of materials that have shown promise for hydrogen storage: metal hydrides, carbon based materials such as carbon nanotubes, and complex hydrides. Although some of the metal hydrides, such as MgH2, have very high gravimetric hydrogen density, they usually have high activation temperatures and release hydrogen slowly. Carbon nanostructures have low gravimetric hydrogen storage density (~ 2 mass%), and are not suitable for on-board application. Recent advances in complex hydrides, especially catalyzed NaAlH4, have shown the reversible adsorption and desorption of up to 4.2 mass% hydrogen at 180 degree C, and have stimulated a lot of research. In order to improve the properties of hydrogen storage materials, there are two general methodologies: finding novel materials, especially complex hydrides, or to tailor the microstructures of existing storage materials, especially into nanostructures. We are interested in the latter .

A fundamental understanding of the hydrogen-nanostructure interaction and the role of nanoscale catalysts in hydrogenation/ dehydrogenation of metal hydrides is vitally important, and it can be achieved only through a critical and systematic investigation on model materials systems that allow for atomistic materials engineering and quantitative structuring, dynamics and property measurements.  In this project, we will critically investigate the mechanism of nano-catalyst mediated hydrogen absorption/desorption in nanostructured metal hydrides using a model system of nanocatalyst decorated/doped Mg nanoblades.  By illustrating the basic process of nanocatalyst-assisted hydrogenation/dehydrogenation, we will cast insights in how and why different nanostructures and nanocatalyst coating change the hydrogen sorption and storage behavior, and what optimal structural and processing parameters are. 

Below are some of our papers on hydrogen storage

Y.-P. He and Y.-P. Zhao, "The role of Mg2Si formation in the hydrogenation of Mg film and Mg nanoblade array on Si substrates," Journal of Alloys and Compounds, online

Y.-P. He and Y.-P. Zhao, “Hydrogen storage and cycling properties of Vanadium decorated Mg nanoblade array on Ti coated Si substrate,” Nanotechnology 20, 204008 (2009).

Y.-P. He and Y.-P. Zhao, “Improved hydrogen storage properties of V decorated Mg nanoblade array,” Physical Chemistry Chemical Physics 11, 255 -258 (2009).

Y.-P. He, Y.-P. Zhao, L. Huang, H. Wang, and R. J. Composto, “Hydrogenation of Mg film and Mg nanoblade array on Ti coated Si substrates,” Appl. Phys. Lett. 93, 163114 (2008).

Y.-P. He, Y.-J. Liu, and Y.-P. Zhao, “Formation of sub-micro MgH2 whiskers during the hydrogenation of Ti doped Mg film,” Nanotechnology 19, 465602 (2008).

W.M. Hlaing Oo, M.D. McCluskey, Y.-P. He, and Y.-P. Zhao, "Strong Fano resonance of oxygen-hydrogen bonds on oblique angle deposited Mg nanoblades," Appl. Phys. Lett. 92, 183112 (2008).

Y.-P. He, Y.-P. Zhao, and J.-S. Wu, “The effect of Ti doping on the growth of Mg nanostructures by oblique angle co-deposition ,” Appl. Phys. Lett. 92, 063107 (2008).