Few-Layer Clayenes for Material and Environmental Applications.

Here, we coined the term "clayene" for a single layer of clay and "few-layer clayene" for clays with 2-10 layers. Few-layer clayenes, which are Fe2+-rich and mica-type, were prepared hydrothermally at 200 °C and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM)/high-resolution transmission electron microscopy (HRTEM) to determine the crystalline phases and morphology, respectively. Chemical composition by energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy confirmed the iron-rich mica composition, and the latter also revealed the presence of both Fe2+ and Fe3+. Mössbauer spectroscopy further confirmed the presence of Fe2+ and Fe3+ and their proportions in the mica-type few-layer clayenes. All of the synthesized mica-type few-layer clayenes except one exhibited high specific surface areas (SSAs) ranging from 94 to 149 m2/g as determined by N2 adsorption-desorption isotherms and the Brunauer-Emmett-Teller (BET) equation. The high surface areas are in conformity with the crystal sizes calculated from XRD peaks and also as revealed by HRTEM. Taking advantage of the interfacial reactions of the high surface area of few-layer clayenes, two potential applications of clayenes were demonstrated in materials and environmental fields.