Ionothermal synthesis of a highly crystalline zirconium phosphate proton conductor.

A highly crystalline one-dimensional zirconium phosphate, (NH 4 ) 2 [ZrF(PO 4 )(HPO 4 )] (ZrP-3), was facilely synthesized by the ionothermal method. The robust structure and rich hydrogen-bonded network make ZrP-3 an excellent proton conductor by having a proton conductivity higher than 10 -2 S cm -1 at 90 °C and 95% RH. The remarkable stability makes ZrP-3 a promising solid electrolyte material for proton exchange membrane fuel cells.