Relationship between the composition of functional groups on the surface of hybrid silicophosphate membranes and their proton conductivity

The surface composition of a set of hybrid silicophosphate membranes has been studied by a method based on the adsorption of acid-base indicators; the relationship between the derived data and the proton conductivity of the test materials has been analyzed. It has been found that the proton conductivity of the membranes increases with an increase in the amount of nearly neutral hydroxyl groups with pK a ∼ 7.3, which slowly dissociate to form protons, and decreases with an increase in the number of acid hydroxyl groups with pK a ∼ 2.5, which exhibit fast dissociation to release protons that are rapidly washed out of the system.