Proton-conducting sol–gel hybrids containing heteropoly acids

Organically modified silicate/heteropoly acid hybrids were made through a sol–gel process from ethoxy silane functionalised by polypropylene glycol of various chain lengths. Heteropoly acids were incorporated as a source of protons. The gels with a high heteropoly acid loading show protonic conductivities of about 10−3 S/cm at room temperature. The process of crystallisation and agglomeration of Keggin units was followed by X-ray diffraction and infrared spectroscopy. The membranes were applied in a direct methanol fuel cell at room temperature.