Specific electrical conductivity in molten potassium dihydrogen phosphate KH₂PO₄ - An electrolyte for water electrolysis at ∼300°C

The conductivity of pure molten KH₂PO₄ salt and four mixtures with more or less water (KH₂PO₄-H₂O and KH₂PO₄-KPO₃ systems, respectively) were measured at temperatures of 240-320°C and under their own water vapor pressures. Molten KH₂PO₄ has been proven to be a promising electrolyte for an elevated temperature pressurized water electrolyzer demonstrating high conductivity of ∼0.30Scm^-1 at 300°C. The conductivity data are given as polynomial functions of temperature and composition. The melting point of the pure salt under its own water vapor pressure was determined to be ∼272°C.