Graphene-wrapped nanocrystals push fuel cell boundaries

March 15, 2016 // By PAUL BUCKLEY
Berkeley Lab has developed a recipe for a battery-like hydrogen fuel cell
Researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a new materials recipe for a battery-like hydrogen fuel cell to push the device's performance forward in key areas.

The fuel cell design surrounds hydrogen-absorbing magnesium nanocrystals with atomically thin graphene sheets. The graphene shields the nanocrystals from oxygen and moisture and contaminants, while tiny, natural holes allow the smaller hydrogen molecules to pass through. The filtering process overcomes common problems degrading the performance of metal hydrides for hydrogen storage.

The graphene-encapsulated magnesium crystals act as 'sponges' for hydrogen, offering a compact and safe way to take in and store hydrogen. The nanocrystals also permit faster fueling, and reduce the overall 'tank' size.

“Among metal hydride-based materials for hydrogen storage for fuel-cell vehicle applications, our materials have good performance in terms of capacity, reversibility, kinetics and stability,” said Eun Seon Cho, a postdoctoral researcher at Berkeley Lab and lead author of a study related to the new fuel cell formula, published recently in Nature Communications.

In a hydrogen fuel cell-powered vehicle using these materials, known as a 'metal hydride' (hydrogen bound with a metal) fuel cell, hydrogen gas pumped into a vehicle would be chemically absorbed by the magnesium nanocrystaline powder and rendered safe at low pressures.

“This work suggests the possibility of practical hydrogen storage and use in the future. I believe that these materials represent a generally applicable approach to stabilizing reactive materials while still harnessing their unique activity - concepts that could have wide-ranging applications for batteries, catalysis, and energetic materials,” said Jeff Urban, a Berkeley Lab staff scientist and co-author.

The research, conducted at Berkeley Lab’s Molecular Foundry and Advanced Light Source, is part of a National Lab Consortium, dubbed HyMARC (Hydrogen Materials - Advanced Research Consortium) that seeks safer and more cost-effective hydrogen storage, and Urban is Berkeley Lab’s lead scientist for that effort.

The U.S. market share for all electric-drive vehicles in 2015, including full-electric, hybrids and plug-in hybrid vehicles, was 2.87 percent, which amounts to about 500,000 electric-drive vehicles out of total vehicle sales of about 17.4 million, according to statistics reported by the Electric Drive Transportation Association, a trade association promoting electric-drive vehicles.