Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy was used to study in detail the water vapor sorption in a short-side-chain perfluorosulphonic acid ionomer membrane (Hyflon® Ion H) suitable for use as electrolyte in Proton Exchange Membranes Fuel Cells. From the analysis of the IR spectra of the membrane at different values of relative humidity (0–0.50) and at 35°C, four types of water molecules, characterized by decreasing strength of interaction with the sulphonate sites of the membrane, were identified. The actual concentration of the various water populations in the membrane was determined through calibration with independent measurements of water sorption: each family exhibits a different shape of the solubility isotherm, corresponding to a specific sorption mechanism. The sorption of the first two populations can be represented with Langmuir isotherms, with each layer adsorbed onto the previous one in a shell-like structure. The other population, are characterized by less strong hydrogen bonding and can thus related to more "free" water absorbed into the matrix. The experimental trends, related to different water populations, were also modeled invoking a simple scheme of equilibrium acid dissociation reactions and obtaining a fairly good agreement
FTIR-ATR study of water distribution in Hyflon-Ion® H membranes / Ferrari M.C.; Catalano J.; De Angelis MG; Sarti GC; Giacinti Baschetti M. - ELETTRONICO. - (2010), pp. 412-414. (Intervento presentato al convegno NAMS (North American Membrane Society) meeting, 2010 tenutosi a Washington DC nel July 17-22, 2010).
FTIR-ATR study of water distribution in Hyflon-Ion® H membranes
DE ANGELIS, MARIA GRAZIA;SARTI, GIULIO CESARE;GIACINTI BASCHETTI, MARCO
2010
Abstract
Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy was used to study in detail the water vapor sorption in a short-side-chain perfluorosulphonic acid ionomer membrane (Hyflon® Ion H) suitable for use as electrolyte in Proton Exchange Membranes Fuel Cells. From the analysis of the IR spectra of the membrane at different values of relative humidity (0–0.50) and at 35°C, four types of water molecules, characterized by decreasing strength of interaction with the sulphonate sites of the membrane, were identified. The actual concentration of the various water populations in the membrane was determined through calibration with independent measurements of water sorption: each family exhibits a different shape of the solubility isotherm, corresponding to a specific sorption mechanism. The sorption of the first two populations can be represented with Langmuir isotherms, with each layer adsorbed onto the previous one in a shell-like structure. The other population, are characterized by less strong hydrogen bonding and can thus related to more "free" water absorbed into the matrix. The experimental trends, related to different water populations, were also modeled invoking a simple scheme of equilibrium acid dissociation reactions and obtaining a fairly good agreementI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
