Enhanced hydroxide ion conductivity of Mg–Al layered double hydroxide at low humidity by intercalating dodecyl sulfate anion

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Ionic conductivity of dodecyl sulfate (DS) anion [CH₃(CH₂)₁₁OSO₃⁻]-intercalated Mg–Al layered double hydroxide (LDH) was examined. Mg–Al DS LDH showed higher ionic conductivity under low humidity than Mg–Al CO₃²⁻ LDH, the most typical LDH. The conductivity of Mg–Al DS LDH was 7.6 × 10⁻⁴ S cm⁻¹ at 80°C 30%RH, whereas that of Mg–Al CO₃²⁻ LDH was 1.1 × 10⁻⁴ S cm⁻¹. This higher ionic conductivity is attributed to the increased amount of the adsorbed water with intercalation of DS anion. The increase of surface water probably provides a path for hydroxide ion conduction, which results in the higher ionic conductivity under low humidity. Additionally, Mg–Al DS LDH retained high ionic conductivity for a longer storage under low humidity.