Intercalation of Lamellar Mineral Kaolinite with 2‐Picolinic Acid: Facile Preparation, Crystal Structure Optimization, and Proton Conductivity

Kaolinite intercalated with 2-picolinic acid was prepared and characterized by scanning electron microscopy, powder X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. The proton conductivity (sigma) of the material is 1.85x10(-10) Scm(-1) at 353 K and gradually increases to 1.7x10(-7) Scm(-1) at 393 K under N-2 (anhydrous environment) with an activation energy of E-a = 1.93 eV, whereas sigma = 1.56x10(-7) Scm(-1) under 80% relative humidity at 353 K with E-a = 0.91 eV. The crystal structure optimized with the Cambridge Sequential Total Energy Package discloses the absence of a dense H-bond network in the layer space of kaolinite, which explains the low proton conductivity and high proton transfer activation energy of the intercalated proton conductor.