Temperature dependent infrared spectroscopy of proton conducting alkali thio-hydroxogermanates

We have investigated the thermal stability and reversibility upon dehydration and re-hydration of a novel class of proton conducting alkali thio-hydroxogermanates. The results indicate that no phase transitions or structural degradation occur in the temperature range 25 to 300 °C, and that repeated dehydration and subsequent re-hydration is a reversible process. The dehydration occurs gradually with increasing temperature, starting at about 80 °C. For temperatures above 180 °C the materials are dry, as all molecular water has been dried off. The dehydration process is shown to be reversible and the material can be rehydrated by exposure to air. The thermal stability and reversibility of the dehydration–rehydration process are attractive properties of functional materials, making the proton conducting alkali thio-hydroxogermanates to potential fuel cell electrolytes.