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Model of confined water self-diffusion and its application to proton-exchange membranes
A model of self-diffusion in confined water is proposed. It is based on the idea that confined water forms structures similar to hexagonal ice and its transport characteristics can be described in the framework of a quasiparticle approach. It is assumed that the quasiparticles responsible for self-diffusion are D- and L-bond defects, which in the case of confined water are interstitial H2O molecules and vacancies in an ice-like lattice. The process of D-defects migration is described as the diffusion of an ideal gas through a porous medium. The analytical expression for the self-diffusion coefficient of confined water depending on the water content quantitatively well describes the experimental data for Nafion-type of proton-exchange membranes.