Atomistic simulation of proton transfer ability of Isopoly acid (IPA)/Heteropoly acid (HPA) doped Nafion® 117 for high-temperature fuel cell applications

Polyoxometalate (POM) doped perfluorosulfonic acid (PFSA) membranes are well-investigated electrolytes for high-temperature fuel cell applications. In the present study, classical and quantum molecular dynamics simulation were used to investigate the morphological features and proton transport properties of isopoly acid (IPA)/heteropoly acid (HPA) doped Nafion (R) 117. This represents the first application of Anderson-type POM as dopant. The composite membrane matrix contains H3PW12O40, H5IW6O24, H9AlW6O24, and H2W6O15. An anion interaction with the side chain increases its phase segregation. Quantum calculation results show that lifetime and half-life of hydrogen bonds (H-bond) decreases in the order: Nafion (R) 117 < IPA doped Nafion (R) 117 < HPA doped Nafion (R) 117. In the HPA doped Nafion (R) 117 matrix, proton can hop faster between H2O molecules than IPA doped one. The membrane containing Anderson-type HPA with Al as heteroatom shows the least activation energy barrier for proton hopping. Besides, the self-diffusion coefficients of H2O and H3O+ of composite membrane were also calculated.