Compact hydrogen storage gets a boost

Solid metal hydrides are seen as a potential fuel source for powering hydrogen vehicles, but are usually limited by slow hydrogen uptake and release. But scientists from Lawrence Livermore National Laboratory (LLNL), working with colleagues from Sandia National Laboratories, Thailand’s Mahidol University, and the National Institute of Standards and Technology, have developed a technique to overcome this.

The researchers found that nanoconfinement - infiltrating the metal hydride within a matrix of another material such as carbon – can have the effect of shortening the diffusion pathways for hydrogen, making the hydride a more efficient fuel source. Using a high-capacity lithium nitride (Li3N) hydrogen storage system under nanoconfinement, they also discovered that internal ‘nano-interfaces’ could alter the phases produced when the material is cycled, further boosting performance. The research is reported in the journal Advanced Materials Interfaces.

"The key is to get rid of the undesirable intermediate phases, which slow down the material's performance as they are formed or consumed,” said Brandon Wood, an LLNL materials scientist and lead author of the paper. “If you can do that, then the storage capacity kinetics dramatically improve and the thermodynamic requirements to achieve full recharge become far more reasonable."

"In this material, the nano-interfaces do just that, as long as the nanoconfined particles are small enough. It's really a new paradigm for hydrogen storage, since it means that the reactions can be changed by engineering internal microstructures.”

According to the team, the discovery that interfaces can play a pivotal role in hydrogen storage materials is not hugely surprising, as engineers have been exploring the same phenomenon in battery electrodes for a few years.

"There is a direct analogy between hydrogen storage reactions and solid-state reactions in battery electrode materials," said Tae Wook Heo, another LLNL co-author on the study. "People have been thinking about the role of interfaces in batteries for some time, and our work suggests that some of the same strategies being pursued in the battery community could also be applied to hydrogen storage.”