Template-free electrosynthesis of crystalline germanium nanowires from solid germanium oxide in molten CaCl_2-NaCl

摘要

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 GeO_2 in molten CaCl_2-NaCl at 600℃ with a current efficiency of ～86% and an energy consumptions as low as 3.26 kW h (kg Ge)~(-1). The cyclic voltammogram of the GeO_2-filled cavity electrode shows that the onset electroreduction potential of GeO_2 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 (GeO_2). The potential applications of the obtained Ge for photodetector and infrared optical window have been also investigated by Raman and FT-IR measurements.