Enabling greener transportation with graphene

Hydrogen storage has proven to be a significant bottleneck to the advancement and proliferation of fuel cell and hydrogen technologies in cars, trucks, and other applications. Rafiee has developed a new method for manufacturing and using graphene, an atom-thick sheet of carbon atoms arranged like a nanoscale chain-link fence, to store hydrogen. His solution is inexpensive and easy to produce.

With adviser and Rensselaer Professor Nikhil Koratkar, Rafiee used a combination of mechanical grinding, plasma treatment, and annealing to engineer the atomic structure of graphene to maximize its hydrogen storage capacity. This new graphene has exhibited a hydrogen storage capacity of 14 percent by weight at room temperature – far exceeding any other known material.

This 14-per cent capacity surpasses the US Department of Energy 2015 target of realising a material with hydrogen storage capacity of 9 percent by weight at room temperature. Rafiee said his graphene is also one of the first known materials to surpass the Department of Energy's 2010 target of 6 percent.

Rafiee's graphene exhibits three critical attributes that result in its unique hydrogen storage capacity. The first is high surface area. Graphene's unique structure, only one atom thick, means that each of its carbon atoms is exposed to the environment and, in turn, to the hydrogen gas. The second attribute is low density. Graphene has one of the highest surface area-per-unit masses in nature, far superior to even carbon nanotubes and fullerenes.

The third attribute is favorable surface chemistry. After oxidizing graphite powder and mechanically grinding the resulting graphite oxide, Rafiee synthesized the graphene by thermal shock followed by annealing and exposure to argon plasma. These treatments play an important role in increasing the binding energy of hydrogen to the graphene surface at room temperature, as hydrogen tends to cluster and layer around carbon atoms.

Talented engineer
Rafiee joined Rensselaer in 2008, following an internship at the City University of Hong Kong and earning his bachelor's and master's degrees in mechanical and manufacturing engineering from the University of Tabriz in Iran. At Rensselaer, Rafiee and his brother, Mohammad, joined the research group of mechanical, aerospace, and nuclear engineering professor Nikhil Koratkar.