Nanocomposite Membrane Materials Based on Nafion and Cesium Acid Salt of Phosphotungstic Heteropolyacid

• Main Authors: E. Safronova, I. Prikhno, G. Yurkov, A. Yaroslavtsev
• Format: Article
• Language: English
• Published: AIDIC Servizi S.r.l. 2015-05-01
• Series: Chemical Engineering Transactions
• Online Access: https://www.cetjournal.it/index.php/cet/article/view/4881

This paper is devoted to the study of the composite (hybrid) Nafion membranes doped by different concentrations of cesium acid salt of phosphotungstic heteropolyacid. The conductivity of the membranes was studied as a function of temperature (at 100 % relative humidity, RH) and RH (at t = 25 °C). Due to the membrane modification, the conductivity increases. At 100% RH, the dependence of conductivity on the dopant concentration passes the maximum at 3 wt.%. Conductivity of hybrid membranes is by 15-20% higher than that of Nafion. Conductivity of the membranes containing = 7 wt.% of CsxH3-xPW12O40 is lower as compared with that of the initial Nafion. Due to the introduction of CsxH3-xPW12O40, conductivity markedly increases at low RH for all concentrations. At RH = 32 %, the maximum conductivity is observed for the membrane containing 5 wt.% of the dopant (2.7·10-3 S/cm) and this value is three times higher as compared with Nafion. Permeability of electrolyte solutions through the membranes is studied. The presence of the dopant with acidic properties decreases the HCl permeability; the higher is CsxH3-xPW12O40 concentration in the membrane, the lower is the diffusion permeability. Hence, the presence of the dopant prevents the diffusion of anions and increases selectivity. The effect of CsxH3-xPW12O40 on the membrane transport characteristics was explained according to the model of the limited elasticity of membrane pores and channels. Hybrid membranes containing minor amounts of CsxH3-xPW12O40 can be considered as promising electrolytes for proton exchange membrane fuel cells due to their high conductivity at low RH and high selectivity.