Efficient proton conductivity of gas-tight nanomembranes of silica-based double oxides

An experiment was conducted to report that protonic conduction is a common feature of amorphous films of many silica-based double oxides and that their sub-100-nm thick membranes can act as effective barriers against diffusion of H₂ molecules. An aluminosilicate film of 100-nm thickness was prepared from a 100 mm mixed sol of AlCl₃ and tetraethoxysilane (TEOS) with atomic ratio of Al/Si = 0.1/0.9 in ethanol. All of the metal alkoxides were used without further purification. Thin films of various metal silicates were prepared from mixed solutions of TEOS and individual metal alkoxides. Appropriate doses of TEOS were added to I-PrOH and then hydrochloric acid. The ITO substrate was treated with oxygen plasma at 10 W under 10 Pa for 10s and immersed in pure water, in order to produce a clean, hydrophilic surface of ITO. It was observed that amorphous nanomembranes contain sufficient acidic sites throughout the membrane interior and that the protons migrate through the membrane matrix.