Brønsted acid–base and –polybase complexes as electrolytes for fuel cells under non-humidifying conditions

A novel series of Brønsted acid–base complexes were prepared by the combination of 2,5-diphenyl-1,3,4-oxadiazole (DOD) with a super strong acid bis(trifluoromethane sulfonyl)imide (HTFSI) at various molar ratios. The DOD–HTFSI complexes showed high ionic conductivities and were electroactive for H2 oxidation and O2 reduction at a Pt electrode. The complexes could serve as fuel cell electrolytes under entirely non-humidifying conditions and at elevated temperatures. The concept of the DOD–HTFSI complexes was applied to a polybase, poly[p-phenylene-2,5-(1,3,4-oxadiazole)] (POD), and the ion-conduction behavior of the POD–HTFSI complexes was discussed with a view to realizing anhydrous solid-state fast proton conductors.