(16e) Molecular Simulation of Ion Transport in the Quaternized Chitosan/Poly(vinyl alcohol) Blend Membrane

Alkaline direct methanol fule cells(ADMFC) have attracted considerable attention, since they can accelerate methanol oxdidation rate, depress the methanol crossover. The anion exchange membrane is the key component, which could affect ADMFC performance significantly. In this paper, molecular simulation methods are used to study the transport behavior of OH- in the anion exchange manbrane prepared with quaternized chitosan(QCS) and poly(vinyl alcohol)(PVA). The diffusion behaviors of OH- ion and water molecule in the membranes are studied. The conductivity of the membrane is caculated through calculation of the self-diffusion coefficient of OH- and application of Nernst-Planck equation. It is found that the calculated conductivities are close to experimental values when the suitable sampling time is adopted. The calculated conductivity increases with increasing temperature or QCS content, which is consistent with experimental results. The conductivity also increases with increasing water uptake. This implyed a close relationship between the conductivity and water uptake existed. Through the pair correlation function analysis of QCS and the distribution analysis of water molecules in QCS/PVA membrane, we found that the structure of OH- ion had a form of HO [H2O] 4- and vehicle mechanism dominated the anion transport.