Solid state protonics is a new reseach field attracting much current attention. One of the most urgent subjects in this field is to create a novel proton conductor, from the viewpoint of developing new energy and energy conservation technologies, including photovoltaic, hydrogen storage and fuel cell technologies. In this work, we report on a proton-conductive organic-inorganic hybrid system, which is a coordination polymer. Such a metal-dimer system with multi-redox property has a large potentiality for the creation of new-functional and high-performance materials in metal-complex solids^1.
We have developed several kinds of proton conductors, which are 1-D, 2-D as shown in Figure, and 3-D coordination polymers. From the complex-plane impedance measurements, all the coordination polymers were found to be highly proton-conductive at room temperature. Among them, H_2dtoaCu exhibits highest proton conduction (〜 10^<-2> S cm^<-1>). This value is comparable to that of Nafion, which is famous for a solid electrolyte of fuel cell. The mechanism of proton conduction is discussed in detail. New highly proton-conductive coordination materials and highly-concentrated hydrogen-storage nano-materials are also discussed.