Self-organized microheterogeneity and high proton conductivity of a solid eutectic of potassium and sodium hydroxides

A new phenomenon is discovered, whereby self-organized microheterogeneity of a NaOH/KOH solid eutectic modifies the properties of this proton conductor and thus changes the characteristics of a related Pd|NaOH/KOH|Pd heterostructure. The basic and applied interest in this phenomenon is related both to a high proton conductivity of the NaOH/KOH eutectic (10–30 mS/cm, which is several orders of magnitude (!) higher than the conductivity of NaOH and KOH alone) at moderate temperatures (360–450 K) and to the special electrochemical properties of the heterostructure. The much greater conductivity in the indicated temperature range and specific features of the low-frequency impedance spectrum are related to the formation of a microheterogeneous mixture of NaOH and KOH crystals in the course of self-organization accompanying solidification of the eutectic. An analysis of the temperature dependence of the eutectic heat capacity reveals the presence of chemically different microdomains of two types with the characteristic volumes of ∼35 and 70 nm 3 .