●  GOALS

The Hydrogen Storage Division brings together leading researchers with expertise in the fundamental design, analysis, and engineering aspects of systems for hydrogen storage. With an emphasis on reducing system weight, volume, and cost, and increasing efficiency, durability, and charge/discharge rates, researchers in this division focus on the design and demonstration of hydrogen systems to enable a sustainable, safe, and affordable method for the storage and transport of hydrogen fuel. Specific goals include elucidating and exploiting the role of defects such as grain boundaries, dislocations, and twins in metallic and intermetallic hydrogen storage materials, and using state-of-the-art characterization tools to describe the microstructural changes that take place in hydrogen storage materials as hydrogen gas is absorbed and released.

●  RESEARCH HIGHLIGHTS AND ACCOMPLISHMENTS

The team had a number of technical accomplishments over the course of the last year. To explore in detail the atomic scale microstructural changes that take place in storage materials during hydrogen absorption and release, the team has developed ex situ transmission electron microscopy tools that are now being applied to hydrogen storage alloys such as Ti,V. Through joint investigations between the Hydrogen Storage and Hydrogen Structural Materials Division, these tools are offering new insights into the microstructural changes that accompany hydrogen absorption and release, which point to the formation of twin boundaries and stacking faults during hydrogenation.

The effects of lattice geometry (lattice size, atomic radii) on hydrogen diffusion kinetics have been explored in Mg-Co alloys, the results of which have initiated new collaborations combining experiment with atomic-scale modeling and simulation at Illinois. Further study has demonstrated the role of nanostructuring and catalysts on the performance of Mg-based materials. In collaboration with the Hydrogen Production Division, the Hydrogen Storage Division demonstrated that grain boundary refinement achieved via high-pressure torsion (HPT) in metallic compounds improves their hydrogen storage capability. Experiments revealed that the grain refinement achieved through HPT is most important for improving the hydrogen absorption rate, pointing to grain boundaries as active storage centers that can be exploited for enhanced performance. HPT was also applied to the nanoscale grain refinement in (typically hard to refine) intermetallic compounds. The team has also demonstrated that HPT-processing of metals such as Pd can minimize structural deformation such as volume expansion during hydrogen uptake.

●  FUTURE DIRECTIONS

Using the newly-developed TEM characterization tools, the team will establish the formation mechanism of lattice defects in Ti,V BCC alloys and other hydrogen storage materials during hydrogenation/ dehydrogenation towards the guided design of high performance materials. In collaboration with nanoscale synthesis and computational modeling capabilities at Illinois, the team will explore geometrical effects on performance. Building on the accomplishments of the team, future efforts will target a number of avenues related to elucidating and exploiting microstructural effects on hydrogen storage. These include continued efforts to exploit HPT for microstructure refinement and enhanced performance. The team will explore the reduction of hydrogen absorption temperature in metallic compounds via the introduction of catalysts, the application of HPT to the hydrogen storage intermetallic FeTi, and the quantitative evaluation of the effect of grain structure on volume expansion and microstructural changes in Pd and other metals of interest during hydrogen cycling.