Maximized proton conductivity of the HPF6 clathrate hydrate by structural transformation

The unique and specific interaction of ionic guests with the surrounding cage framework might play a key role in promoting the electrochemical properties of ionic clathrate hydrates. In this work we focus on addressing (1) structural transformation simply due to an increase of water content, (2) structure-dependent ionic conductivity, (3) the existence of maximum ionic conductivity at a specific hydration number, and (4) proton migration through channels in the crystalline hydrate matrix. The melting temperature and ionic conductivity of hexafluorophosphoric acid hexahydrate (HPF6-6.0H(2)O) are found to be approximately 29.5 degrees C and 10(-1) S.cm(-1). respectively, showing that HPF6 center dot 6.0H(2)O possesses desirable features as a solid proton conductor.