Organic–inorganic hybrid titanophosphite proton conductive membranes with graded monomer conversion

Further advances in polymer electrolyte fuel cells require membranes that can operate at intermediate temperatures between 100 and 150 °C. In this study, we report a unique organic–inorganic hybrid titanophosphite membrane possessing high proton conductivity at such intermediate temperatures. The membrane was prepared to have a graded monomer conversion from its surface to its inner parts, by ultraviolet light (UV) absorption of titanate during UV-initiated photopolymerization. The surface of the membrane was completely polymerized to be water durable, whereas its inner parts were weakly polymerized, thus allowing VPA to function as a proton donor. This gives proton conductivities that are as high as 6.3 × 10− 4 S cm− 1 at 130 °C under a dry atmosphere.