College of Social & Natural Sciences

Hydrogen dynamics in complex hydrides using proton nuclear magnetic resonance

1. Background

As early as the mid-nineteenth century, the ability of metals such as copper and palladium to absorb large amounts of hydrogen gas was stimulating research^1,2.  Recent investigations of hydrogen absorbing materials, hydrides, have been driven by both scientific interests and geopolitical concerns.  It is widely argued that electric vehicles drawing power from hydrogen fuel cells could be an environmentally sound solution to the energy crises ^3--5.  Because hydrides show tremendous potential as hydrogen storage devices when compared to other methods ⁶, the physical properties of hundreds of hydrides have been investigated ^7,8.  However, a practical hydrogen storage system for mobile applications must minimize storage volume, maximize hydrogen weight fraction, and allow rapid and reversible hydrogen movement. As yet, no hydride that meets all the US Department of Energy performance standards is known⁸. 

Understanding this mechanism is of considerable scientific and technological interest, potentially leading to catalysts for new complex hydrides¹⁰, improvements in hydrogen absorption/desorption characteristics such as reversibility, temperature, pressure, and duration. 

This research will advance the understanding of hydrogen dynamics in complex hydride systems, and test predictions resulting from established models of hydrogen environments and dynamics. The technique that will be used is nuclear magnetic resonance (NMR).  There is currently a gap between models of hydrogen dynamics and experimental corroboration.  We will use NMR to address the questions:   

• Which aspects of the competing hydrogen dynamics models^11,13 are correct? 
• Are models that predict the dependence of hydrogen dynamics on particular variables such as extended defects in the crystal grains correct¹¹? 
• How does hydrogen dynamics differ across similar complex hydride systems? 
• What is the nature of hydrogen dynamics in relevant complex hydrides that have gone as yet unstudied?