Rachel Aga (Advisor), Paul Seybold (Committee Member), Ioana Sizemore (Committee Member)
Master of Science (MS)
Computational modeling using classical grand canonical Monte Carlo simulations and first-principles calculations were carried out to study the adsorption of molecular hydrogen on nanoporous carbon modeled by the slit- pore geometry. It has previously been shown that hydrogen adsorption on pristine porous carbon has dependence on pore size and that an optimum pore size, which exhibits the maximum mass uptake, exists. There have been suggestions that doping graphitic nanocarbon structures with Pd enhances their adsorption capacity. The pore-size dependence of this change in adsorption brought about by Pd and the conditions at which improvement in adsorption can occur have not been extensively addressed to date. In this work, we perform computational modeling to examine hydrogen adsorption on pristine carbon and Pd-doped carbon nanopores. First-principles calculations were used to generate minimized configurations of the sorbent system while grand canonical Monte Carlo simulations modeled the finite temperature and pressure adsorption of hydrogen. We perform simulations at 298 K and pressures of 0.01 MPa, 1 MPa, and 5 MPa for systems with Pd to C ratios of 1:32, 1:18 and 1:8. Among the systems examined, pristine carbon at 5 MPa exhibited the highest mass uptake at 4.2 wt % adsorption capacity. This is consistent with the expectation that as the gas reservoir pressure increases, the adsorption capacity also increases. The presence of Pd resulted to enhancement in adsorption only at 0.01 MPa, the lowest pressure investigated. For the maximum adsorption of 4.2 wt% at 5 MPa, the heat of adsorption was calculated to be 8 kJ/mol. The target heat of adsorption value for hydrogen storage materials is 25 kJ/mol, and this was achieved for the 1:8 Pd:C ratio at a pore size of 6 Angstroms, but the system showed a lower adsorption capacity of 1.5 wt%.
Department or Program
Department of Chemistry
Year Degree Awarded
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