Synthesis of a Ternary Thiostannate with 3D Channel Decorated by Hydronium for High Proton Conductivity

Metal chalcogenides with various channel structures feature a number of interesting properties including fast-ion conductivity and selective ion exchange. Most of these compounds are popularly prepared based on the templates of organic amines that play the part of a structure directing agent and even structure-building units, while it still remains a challenge as to the organotemplate-free synthesis for these compounds. Here, a new ternary thiostannate (H₃O)₄Cu₈Sn₃S₁₂ was synthesized through a facile, efficient, and organotemplate-free route under hydrothermal conditions. The framework of (H₃O)₄Cu₈Sn₃S₁₂ consists of [Cu₈Sn₆S₂₄]^8- building units and possesses a 3D interconnected 8-ring channel structure decorated by pure hydroniums, which not only balance the charges but also facilitate the proton conductivity. The proton conductivity reaches as high as 1.03 × 10^-3 S cm^-1 at 393 K under anhydrous conditions, which is 2 orders of magnitude higher than that of (H₃O)₂(enH₂)Cu₈Sn₃S₁₂, a similar channel structure compound prepared by using ethylenediamine as an organic template.