Proton Conduction in the Polymer Electrolyte Membrane: molecular and statistical mechanics modeling
Keywords: PEM Fuel cell
For the PEM fuel cell to be successfully integrated into the mass-market new materials will need to be developed, including: electrocatalysts for the fuel and air electrodes and the proton conducting membrane . New materials possessing improved properties will emerge as a result of a collaborative effort between experimentalists, engineers, and theorists, the later doing both device and materials modeling. For the physical and chemical modeling of materials to play a role in the suggestion of new materials the modeling must be at the nano- and even molecular scale and ideally it should not be phenomenological but rather from “first principles”.
The hydrated PEM is an inhomogeneous material the morphology of which is not well characterized. As such it is a system that must be examined through modeling at several distinct length and time scales. Our approach has been to theoretically examine proton conduction in the PEM at three distinct length and time scales implementing three different approaches [2-9]. The hierarchy of this multi-scale modeling is as follows: (1) proton dissociation and hydration of hydrophilic groups in the membrane using ab initio molecular orbital theory; (2) local proton dynamics ‘near’ (between) the fixed sites studied with ab initio (quantum) molecular dynamics; and (3) proton diffusion and the state (permittivity) of the water within a single membrane pore or channel applying both equilibrium and non-equilibrium statistical mechanics.
This talk will present new results and analysis of proton conduction derived from the three approaches described above and at various degrees of hydration with various membranes.
NSTI Nanotech 2003 Conference Technical Program Abstract