Apr 24, 2009
Nanoblade array confronts hydrogen storage bottleneck
Storage is the bottleneck when it comes to using hydrogen energy for on-board vehicle applications. Magnesium hydride is one of the most promising candidates for future solid-state hydrogen storage thanks to its light weight, low cost and highly reversible hydrogen storage capacity of 7.6 mass% in MgH2. There are obstacles to overcome though. The material's high thermodynamic stability and sluggish reaction kinetics limit its practical applications, but here, engineering magnesium into nanostructures and adding an appropriate transition metal catalyst could help.
To investigate the concept, researchers at the University of Georgia, US, have designed and fabricated a vanadium-decorated magnesium nanoblade array structure (shown above) by coating a thin layer of vanadium onto the two sides of individual magnesium nanoblades. The structures were made using a dynamic shadowing growth (DSG) technique, which is based on a physical vapor deposition method and combines oblique angle deposition (OAD) with substrate manipulation and source control.
The catalytic role of the vanadium coating in the formation and decomposition of MgH2 and the unique nanoblade morphology with large surface area and small hydrogen diffusion length contribute to an overall improvement in hydrogen sorption performance. Specifically, the hydrogen sorption activation energy is reduced from 120–150 kJ/mol H2 for magnesium films or powders to ~35 kJ/mol H2, the hydrogen uptake and release temperatures are reduced even to room temperature, and the hydrogen loading and unloading times are reduced from 50 hours to several minutes.
The team reported its work in a special issue of Nanotechnology.
About the author
Dr Yuping He is a postdoctoral researcher in Prof. Yiping Zhao's group at the Nanoscale Science and Engineering Center and Department of Physics and Astronomy, University of Georgia, Georgia, US. She is working mainly on the hydrogen storage properties of magnesium-based nanostructures, which is supported by a DOE Hydrogen Initiative Award.