Investigations on the proton transport mechanism in potassium dihydrogenphosphate

Abstract

Transference number, mobility, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and electrical conductivity as a function of temperature and humidity are reported on polycrystalline pellets and single crystals of potassium dihydrogenphosphate. The proton transport is anisotropic, the c axis being more favoured. The mobile species are H⁺ and OH^-. The mobile species are the result of a threefold rotation of H₂PO₄^- unit about any of the axes of PO₄ tetrahedra giving O...H...H...O bonding, which rearranges as H...O...H...O. The H...O...H bridge is electrodissociated to give H⁺ and OH^-. Finally, a P-O-P bond is formed between electrolysed H₂PO₄^- groups.