Hydrothermal Synthesis and Characterization of K_xMnO₂·yH₂O

Abstract

We report here the direct synthesis of a hexagonal form of manganese dioxide using mild hydrothermal methods. The reaction of potassium or sodium permanganate in water at 170 °C leads directly to potassium or sodium manganese dioxide, Alk≈0.25MnO2·0.6H2O, with a R3̄m rhombohedral structure like Li x (H2O)TiS2 and a 7 Å repeat distance indicative of a monolayer of water between the manganese dioxide layers. This manganese oxide reacts readily and reversibly with lithium ions.

Decolorization of methylene blue in layered manganese oxide suspension with H2O2

“…1. The characteristic peaks at 002, 212, 144 and 161 marked with asterisks (*) were assigned to a well-crystallized Na-Birnessite (JCPDS 23-1046) [31]. Moreover, the peak at 002, representing the Mn-Mn distance from adjacent layers, was especially significant.…”

Materials and fabrication of electrode scaffolds for deposition of MnO2 and their true performance in supercapacitors

“…If the reaction occurs at elevated temperature (hydrothermal condition) and/or acidic solution, the self-decomposition of MnO À 4 according to [249,250]:…”

Structure of synthetic Na-birnessite: Evidence for a triclinic one-layer unit cell

“…A three-layer hexagonal modification was synthesized recently under hydrothermal conditions (Chen et al 1996). However, the most common way to synthesize NaBi is the formation at room temperature and high pH of Na-rich 10Å buserite, which is then partially dehydrated to form NaBi (Giovanoli et al 1970a;Feng et al 1997).…”