Electrochemical properties of protic ionic liquids: correlation between open circuit potential for H-2/O-2 cells under non-humidified conditions and Delta pK(a)

Electrochemical measurements for a series of protic ionic liquids revealed that open circuit potential (OCP) for H-2/O-2 cells increases with increasing Delta pK(a) of the constituent acid and base and passes through a maximum to gradually fall for further increase in the Delta pK(a), which indicates the reliance of the electrochemical activity on the persistence of non-ionic species and on the meagre proton activity due to strong N-H bonds.