Nanocomposites and nanomaterials

Proton conducting membranes modified with nanoparticles of tin(IV) phosphate
Dzyazko Yu.S1, Fedina I.V.1, Ponomarova L.M.2, Yatsenko T.V.1
1V.I. Vernadskii Institute of General and Inorganic Chemistry of the NAS of Ukraine, 32/34 Palladin ave., 03142, Kyiv, Ukraine
E-mail:  fedinairyna8@gmail.com
2Department of Theoretical and Applied Chemistry, Sumy State University, Rymskii-Korsakov 2, 40000, Sumy, Ukraine

For proton-conducting membranes, which are used in fuel cells, an important problem is the storage of significant electrical conductivity under elevated temperatures, which prevents platinum catalyst poisoning. The solution to the problem is the incorporation of an inorganic ion exchange component into the polymer. However, the modifier can ambiguously affect the functional properties of membranes: the result of modification can be both their improvement and deterioration. This problem is due to the complex porous structure of swollen ion exchange membranes, which includes hydrophilic micro- and mesopores, as well as hydrophobic meso- and macropores. The modifier can be deposited at different pores, the size of which determines the geometric parameters and morphological features of the incorporated particles. The aim of this work is to develop methods for obtaining the same type of particles in ion exchange polymers.
The Nafion-117 membrane (was modified with nanoparticles of tin(IV) hydrophosphate (THP). The synthesis methods involved the deposition in the polymer matrix of only non-aggregated nanoparticles or aggregates (globular or dendritic). Native particles are located in hydrophilic pores, and aggregates in hydrophobic pores. Materials containing massive agglomerates in hydrophobic macropores were also obtained. Under conditions of constant temperature, the electrical conductivity of membranes containing different amounts of water was studied. The dependence of the electrical conductivity of membranes on the water content is percolation. For a temperature of 20° С, it was found that aggregates increase the percolation threshold, and unaggregated nanoparticles decrease it. Thus, membranes that are modified by nanoparticles are able to retain electrically conductive properties while reducing the water content. The function of the water accumulator is performed by the surface of nanoparticles, where the bound water is concentrated. A similar effect is observed at 100 ° C for a membrane modified with non-aggregated THP nanoparticles. In this case, the membranes that contain nanoparticle aggregates do not exhibit conductive properties.