Proton conducting polymer electrolytes for CO sensors

Abstract

Commercially available CO sensors suffer from many drawbacks most important of all is the dependence of their performance on changes in humidity. The objective of this work is to develop a non-aqueous proton conducting polymer to overcome such a problem. IMI. Poly(vinyledenefluoride-co-hexafluoropropylene), of A novel ionic liquid consisted of a mixture of imidazole and imidazolium bis- (triflouromethanesulphonyl imide) solids, The liquid was introduced into poly(vinyledenefluoride), FVdF, PVdF-HFP, poly(epichlorohydrin-co-ethyleneoxide), poly(methylmethacrylate), PMMA and PVdF-HFP polymeric hosts in order to obtain homogeneous films. Compatibility of the polymer hosts with IMI was first addressed. PEE and the (PMMA/PVdF-HFP) blend gave homogenous films whereas IMI mixtures with PVdF or PVdF-HFP were phase segregated. The latter became homogenous upon addition of propylene carbonate, PC. Conductivity of the films were studied as a function of IMI content, where a linear behaviour was observed between the logarithm of the conductivity versus the IMI content. A percolation threshold was proposed to explain the observed break point in the conductivity dependence of the PVdF-HFP:IMI films. XRD, TGA and DSC were used to characterise the films. blend PEE and a A planar amperometric CO sensor was fabricated using a IMI:PC:PVdF-HFP film. The sensor showed no response without being pre-equilibrated with water. The sensor response and tgo were found to be dependent on the CO concentration and relative humidity. Cyclic Voltammograms were performed on a Pt electrode in a IMI:PC solution. It was concluded that water was very crucial for the CO oxidation. A new gap electrode method was developed to measure the conductivity of the films. The results showed that uncontrollable variations in either the polymer conductivity or the geometry or both have made it difficult to fit the systematic variation to the theoretical model. Nevertheless, acceptable conductivity values were obtained for the polymers by a combined normalization/iteration method. The technique should therefore be generally applicable given better control of polymer uniformity and thickness.

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