Conversion Of Gypsum Into A Superprotonic Conductor

Abstract

Development of superprotonic conductors of inexpensive and environmentally stable inorganic materials is important for clean energy fields such as H2-O2 fuel cells and hydrogen energy technology. We will show that gypsum (CaSO4·2H2O), normally an insulator, can be easily converted into a superprotonic conductor by a new processing method using phosphoric acid.The proton conductivities of the modified gypsums reach ∼ 10−2 S cm&minus1 at room temperature. Fuel cells (1 atm dry-H2)/(air), using 1 mm thick plates of the modified gypsums, give a power density of 0.15 mW cm−2 at room temperature. The high proton conductivities of the modified gypsums are discussed in terms of their x-ray diffraction patterns and IR spectra.