Hydrogen is widely considered an essential part of our energy future as a potential medium for energy storage (its combustion byproduct being merely water vapor), however due to the fact that hydrogen is a gas, the "grand challenge" is the development of a storage system capable of delivering acceptable driving ranges. The problem is that currently we lack a "goldilocks" material--a material that interacts with hydrogen "just right," either the materials bind hydrogen too strongly (making it hard to remove it from the tank) or too weakly (making it hard to store it).
In my group we use a combination of theoretical modeling and computer simulations to investigate "nano-sponges"--materials with pores in the nanometer scale--that are capable of storing hydrogen and natural gas (methane) reversibly by physisorption at moderate pressures. In particular we seek to under-stand how the nanopores can be engineered (optimal pore size and geometry, chemical surface functionaliation) to enhance the hydrogen-pore interaction. For example, we demonstrated theoretically by ab initio calculations and grand canonical Monte Carlo simulations how boron doping of carbon could raise the interaction energies substantially creating a material capable of reaching acceptable storage characteristics at room temperature, which was experimentally confirmed. We are also working to develop the theoretical foundations of new experimental methods to characterize porous materials.
In addition, we also investigate the curious phases and phase transitions observed in numerous quasi-two dimensional systems such as two-dimensional electron systems (Quantum Hall Effects), spins and spin chains ("Extended Universality"), and organic films deposited on a substrate.
Access Publications at Google Scholar here.
Enhanced hydrogen adsorption in boron substituted carbon nanospaces, L. Firlej, Sz. Roszak, B. Kuchta, P. Pfeifer, and C.Wexler, J. Chem. Phys. 131, 164702 (2009).
Multiply Surface-Functionalized Nanoporous Carbon for Vehicular Hydrogen Storage, P. Pfeifer, C. Wexler, P. Yu, G. Suppes, F. Hawthorne, S. Jalisatgi, M. Lee, and D. Robertson, Department of Energy Annual Progress Re-port 2011, 444.
Sub-Nanometer Characterization of Activated Carbon by Inelastic Neutron Scattering, R.J. Olsena, L. Firlej, B. Kuchta, H. Taub, P. Pfeifer, and C. Wexler, Carbon 49, 1663 (2011).
Recoiling and Bound Quantum Excitations of Adsorbed Hydrogen Measured by Inelastic Neutron Scattering, R. Olsen, M. Beckner, M. Stone, P. Pfeifer, C. Wexler, and H. Taub, Phys. Rev. Lett. (under review, 2011).
Novel Liquid Crystalline Phases in Quantum Hall Systems; C. Wexler and O. Ciftja; Int. J. Mod. Phys. B 20; 747-778 (2006).
Universality away from critical points in two-dimensional phase transitions; C.M. Lapilli, P. Pfeifer, and C. Wexler; Phys. Rev. Lett. 96, 140603 (2006).
Melting of hexane monolayers adsorbed on graphite: the role of domains and defect formation; C. Wexler, L. Firlej, B. Kuchta, M.W. Roth; Langmuir Letters 25, 6596-6598 (2009).