Combinatorial approach to material synthesis and screening of hydrogen storage alloys

Abstract

The development of a practical fuel cell powered automobile is now the focus of intense competition. Full exploitation of the advantages of a fuel cell will require the development of a practical hydrogen storage medium. We introduce the use of thin-film combinatorial methods to synthesize hydrogen storage alloys and demonstrate the use of spatially resolved infrared imaging as a high throughput hydrogen storage candidate screening technique. Using a combination of pulsed laser deposition and magnetron sputtering, multi-compositional samples were produced for hydrogen sorption studies. Analysis is presented of a sample that consists of 16 separate Mg–Ni–Fe ternary pads and 32 Mg–Ni or Mg–Fe binary pads. Hydrogen sorption related emissivity changes observed indicate a substantial decrease in hydriding temperatures, which sensitively depend on composition.

Observation of phase transitions in hydrogenated Yttrium films via normalized infrared emissivity

“…The 10 min point roughly corresponds with the beginning of the second sigmoid in the IR curve; where YH 3 has begun to form. The lack of evidence for YH 3 in the X-ray diffraction is likely related to the formation of a thin layer of YH 3 near the surface, which is not of sufficient volume fraction to be measured by XRD, but is picked up by the extremely surface sensitive IR emission.…”

“…Finally, after 24 h the hydrogenation has been completed and XRD shows only the presence of YH 3 . PGAA confirms that after 24 h the H/Y ratio is 3.…”

“…The method is based on the electronic changes of a film as hydrogen is admitted (e.g., Fermi energy shifts to a region of lower density of states), which affects the strength of IR emission [3]. The often-occurring metal-to-insulator transitions present during the hydrogenation of metallic films results in an increase in the normalized IR emissivity of the sample.…”

Mg-Based Thin Films as Model Systems in the Search for Optimal Hydrogen Storage Materials

“…Upon hydrogenation the material becomes optically transparent and the IR camera will see the bright region at the point where the hydride is forming. The IR screening method was introduced by Olk [7,8]. Oguchi et.al used the method, combined with structural characterization, to determine the rate of a hydride phase growth [9].…”

In situ infrared thermographic screening of compositional spread Mg–Ti thin-film libraries

“…Solid hydrides presenting high volumetric and gravimetric densities are needed to provide all the technical and economic requirements for the real development and implantation of such technology. In order to speed up efforts to find lightweight metal and complex hydrides as promising storage materials, a great deal of work has been done in recent years to develop combinatorial synthesis and high-throughput screening methodologies, mainly based on the thin-film approach [1][2][3][4][5][6][7][8][9][10][11].…”