(213b) Dynamics of Anhydrous Proton Transport on the Surface of Functionalized Graphene

Authors: 
Bagusetty, A., University of Pittsburgh
Choudhury, P., New Mexico Institute of Mining and Technology
Saidi, W. A., University of Pittsburgh
Derksen, B., University of Pittsburgh
Johnson, J. K., University of Pittsburgh
Proton transport phenomena has been of tremendous importance for the application of proton transport membrane fuel cells for their efficiency and clean emissions. We are specifically focused with the applications of proton transport at interfaces for a better design of new materials for proton exchange membrane (PEM) fuel cells in anhydrous conditions. Study of transport of protons over the surface of hydroxylated graphene in anhydrous conditions is performed using density functional theory. The hypothesis is that a facile anhydrous proton transport will occur on a surface that has a continuous network of hydrogen bonded hydroxyl groups showing "grotthuss-like" mechanism. Simple configurations of 1-D single file and a 2-D hydrogen bonded network of hydroxyl groups on graphane membrane will sufficiently facilitate the transport of protons. Dynamical properties and energetics related to the transport of the excess proton is studied. In this work, facile transport of excess proton over the surface of functionalized graphene has been confirmed with computed energy barriers using nudged elastic band technique and their respective mechanism pathways will be discussed. Ab-initio molecular dynamics (AIMD) simulations are used to determine the dynamical properties of 1-D single file and 2-D network of fully hydroxylated graphene surface with one excess proton concentration. Correlations influencing the dynamical properties for the above patterns of hydroxylation are investigated. Stability of the functionalized graphene material for varying degree of hydroxylation, morphological defects and also excess proton concentrations will be reported. A monte-carlo based lattice model of 1-D hydrogen bonded network system mimicking the proton hopping mechanism observed from the AIMD simulations is developed. This is to support and verify the behavior of normal diffusion of excess proton transport for larger system size and longer time domain.