Graphene as the Ultimate Membrane for Gas Separation
Key Challenges: Investigate the permeability and selectivity of graphene sheets modified with custom-designed sub-nanometer pores. Since graphene is impermeable to nearly all gases this means having to “drill holes” in the graphene sheet by "virtually" removing two neighboring rings from a graphene sheet and substituted either hydrogen or nitrogen atoms to create two different molecular sieves with roughly 0.3-nanometer openings.
Why it Matters: Graphene is a single-atom–thick flat sheet of carbon atom rings arranged in a honeycomb lattice. It is prized for a range of extraordinary properties that make it useful for products ranging from computer displays and flat panel TVs to ATM touch screens and solar cells. But now electronic structure computations carried out solely at NERSC have suggested a new role for this impressive material, one that could have widespread impact on numerous energy and technological applications, including carbon sequestration, fuel cells, and industrial gas separation.
Accomplishments: The Jiang group used first principles density functional theory (DFT) with planewave bases and periodic boundary conditions to explore the potential energy surface and dynamics of hydrogen (H2) and methane (CH4) molecules passing through their subnanometer pores. They found astonishing H2/CH4 selectivity -- on the order of 108 and 1023 for the N-functionalized and all-H pores, respectively. Since their pores present a formidable barrier for CH4 but easily allow H2 to pass -- much more so than traditional polymer and silica membranes used for gas separation -- their results may suggest a way to potentially lower energy costs for purification and production of these key industrial gases.
Investigators: Dr. De-en Jiang, Valentino R. Cooper, and Sheng Dai, Nanomaterials Chemistry Group (Oak Ridge National Laboratory)
More Information: ACS Nano Letters, 2009, 9 (12), pp 4019–4024, and the ORNL Nanomaterials Chemistry Group web site.
About NERSC and Berkeley Lab
The National Energy Research Scientific Computing Center (NERSC) is the primary high-performance computing facility for scientific research sponsored by the U.S. Department of Energy's Office of Science. Located at Lawrence Berkeley National Laboratory, the NERSC Center serves more than 4,000 scientists at national laboratories and universities researching a wide range of problems in combustion, climate modeling, fusion energy, materials science, physics, chemistry, computational biology, and other disciplines. Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California for the U.S. DOE Office of Science. For more information about computing sciences at Berkeley Lab, please visit www.lbl.gov/cs.