Synthesis and properties of TiO2-P2O5 and SiO2-TiO2-P2O5 porous hybrids obtained by templating in highly concentrated emulsions
By L.A. P
Published in Ceramics International
2016
Abstract
Hybrid inorganic oxides which have simultaneously meso- and macro-porous texture leading to high surface area and high pore volume were prepared by templating in polystyrene monoliths in highly concentrated emulsions. The synthesis was carried out by a two-step method. In the first step, macroporous polystyrene monoliths were prepared using highly concentrated Water-in-Oil (W/O) emulsions as templates, by polymerizing in the external phase of the emulsions. In the second step, the polystyrene monoliths were impregnated with TiO2-P2O5 or SiO2-TiO2-P2O5 sol-gel precursors. Using sol-gel condensation reactions, hybrid inorganic oxide materials were successfully obtained with complex porous structures. The porosity was characterized by electron microscopy (SEM and TEM), and nitrogen sorption. Nitrogen isotherms confirmed that binary TiO2-P2O5 hybrid materials were mainly macroporous while ternary hybrid SiO2-TiO2-P2O5 had all sorts of pores; micropores, mesopores and macropores, with surface area around 300 m2/g. Preliminary electrochemical evaluation of these materials has been performed, aiming at possible applications as elements in Proton Exchange Membrane Fuel Cells (PEMFC). Results of conductivity, obtained by Electrochemical Impedance Spectroscopy (EIS) have shown excellent proton conductivity, particularly at low temperatures. Most likely, this is a consequence of high water retention capacity, in small interconnected pores, and acidity provided by P