Ammonium based ionic liquids immobilized in large pore zeolites: Encapsulation procedures and proton conduction performance

Ammonium based ionic liquids immobilized in Y (FAU framework code) and beta (BEA framework code) type zeolites by different solution methods have been comprehensively characterized for their potential applications as hydrophilic-conducting fillers for PEM. In particular (2-hydroxymethyl) trimethylammonium dimethyl phosphate (IL1) and N,N-dimethyl-N-(2-hydroxyethyl) ammonium bis(trifluoromethanesulfonyl) imide (IL2) encapsulated into commercial NaY (Si/Al = 1.5) and NH 4-BEA (Si/Al = 12.5) type zeolites have been investigated. X-ray diffraction, N 2 physisorption, TGA analysis, ATR–FTIR and Raman spectroscopy techniques have been used to assess about the goodness of the encapsulation procedures. Finally, A.C. impedance spectroscopy measurements of tablets prepared from PVDF/composite (1:9 wt. ratio) were performed in order to evaluate their conduction properties. The conduction properties of the composites as a function of temperature and water partial pressure have been finally chosen as analytical tool to define the best encapsulation procedure and IL/Z composite for PEMFCs applications. A possible conduction mechanism, where synergic-inhibition effects between ILs and H 2O molecules coupled to IL dragging by water desorption take place, is also presented.