Template-free electrosynthesis of crystalline germanium nanowires from solid germanium oxide in molten CaCl2-NaCl

Germanium nano-materials are attractive due to their potential application prospects in electronic, information and energy industry. Herein we report a one-step preparation of crystalline germanium nanowires (Ge-NWs) by direct electrochemical reduction of solid GeO2 in molten CaCl2-NaCl at 600 degrees C with a current efficiency of similar to 86% and an energy consumptions as low as 3.26 kW h (kg Ge)(-1). The cyclic voltammogram of the GeO2-filled cavity electrode shows that the onset electroreduction potential of GeO2 is -1.0 V vs. Ag/Ag+, much more positive than the reduction potential of cations in the melt. The as-prepared Ge-NWs are of high aspect ratio, high purity and good crystallinity according to the XRD, EDX, SEM and TEM characterizations. The present approach provides a simple and short process for the production of Ge-NWs from a cost-affordable germanium precursor (GeO2). The potential applications of the obtained Ge for photodetector and infrared optical window have been also investigated by Raman and FT-IR measurements. (C) 2013 Elsevier Ltd. All rights reserved.