Open AccessAn Electrochemical Approach toward the Metastable Type II Clathrate Germanium Allotrope
Author(s) -
Bodo Böhme
Publication year - 2020
Publication title -
inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 233
eISSN - 1520-510X
pISSN - 0020-1669
DOI - 10.1021/acs.inorgchem.0c01796
Subject(s) - chemistry , microcrystalline , electrochemistry , electrolyte , alkali metal , molten salt , germanium , iodide , anode , powder diffraction , fast ion conductor , chemical engineering , inorganic chemistry , crystallography , electrode , organic chemistry , silicon , engineering
By using an anodic conversion process at 280 °C, the type II clathrates Na 1.7(6) Ge 136 and Na 23.0(5) Ge 136 were obtained from Na 12 Ge 17 as the starting material. An alkali-metal iodide molten-salt electrolyte complied with the reaction conditions, allowing for the formation of microcrystalline products. Characterization by powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy also revealed Na 4 Ge 13 as an intermediate and α-Ge and Cs 8- x Ge 136 as byproducts, with the latter likely resulting from cation exchange between the starting material and electrolyte. Taking such minor side reactions and a small contribution of material without suitable electrical contact into account, anodic conversion of Na 12 Ge 17 to Na 1.7 Ge 136 proved to proceed without parasitic processes and to comprise the material bulk. The hitherto existing preparation method for Na x →0 Ge 136 by gas-solid oxidation of Na 12 Ge 17 has thus been translated into a scalable high-temperature electrochemical approach with enhanced tools for reaction control, promising access to pure Ge( cF 136) and Na 24 Ge 136 after process optimization.