Template‐Free Electrochemical Formation of Silicon Nanotubes from Silica

Abstract

Silicon, with its elaborate microstructure, plays important roles in energy materials. In operando engineering of microstructure during extraction is an ideal protocol to develop advanced Si‐based materials. A template‐free electrochemical preparation of silicon nanotubes (Si‐NT) is herein achieved by co‐electrolysis of SiO2 and AgCl in molten NaCl–CaCl2 at 850 °C. The in situ electrodeposited Ag facilitates the generation of a liquid Ag–Si intermediate, triggering a liquid–solid mechanism to direct the growth of Si‐NT. An automatic separation of Ag from Si then occurs in the following cooling process, resulting in Ag deposits on the Ni current collector and recycling of Ag. Such a facile and smart preparation of Si‐NT from affordable silica guarantees an enhanced current efficiency of 74%, a decreased energy consumption of 12.1 kW h kgSi−1, and enhanced lithium‐storage capability of the electrolytic Si‐NT. An in situ coating of Ag over the Si‐NT can also be fulfilled by simply introducing soluble AgCl in the melts. The present study provides a template‐free preparation and an in situ surface modification of Si‐NT.

Electrochemical Fixation of Carbon Dioxide in Molten Salts on Liquid Zinc Cathode to Zinc@Graphitic Carbon Spheres for Enhanced Energy Storage

“…When the cathodic potential is sufficiently negative, the rate‐determining step is the diffusion of reactive species rather than the electrochemical polarization. [ 21 ] Diffusion of soluble CO 3 2− is much easier than that of solid ZnO, which means that the co‐reduction of CO 3 2− and ZnO gradually turns to the dominant reduction of CO 3 2− with the shift of the cathode potential toward the negative direction. Therefore, homogeneous nucleation of carbon on the carbon flakes is dominant at large negative potentials, leading to generation of less Zn@C spheres (Figure S3, Supporting Information).…”

“…When the cathodic potential is sufficiently negative, the ratedetermining step is the diffusion of reactive species rather than the electrochemical polarization. [21] Diffusion of soluble CO 3…”

“…[ 6 ] The wide electrochemical window of molten salt electrolytes promises a high current efficiency of the electrochemical reduction of CO 2 in molten salts. [ 6,20–24 ] The high‐temperature environment of inorganic molten salts brings about enhanced mass transfer and facilitated reaction kinetics, enabling an appealing conversion rate of CO 2 free of any precious catalysts. [ 6,14,15 ] Molten salts possess a high heat capacity, which means the heat required by the molten salt fixation of CO 2 can be supplied by solar‐thermal systems.…”

Controllable conversion of rice husks to Si/C and SiC/C composites in molten salts

“…Molten salt has been proven to be a favorable medium for both electrochemical conversion of SiO 2 to Si and pyrolysis conversion of organic mass to carbon [13][14][15][16][17][18][19][20]. Therefore, integrating of pyrol-ysis and electrolysis in molten salts into one alliance, namely, thermoelectrolysis, to realize the simultaneous conversion of organic mass and SiO 2 in RHs to Si/C composites can realize killing two birds with one stone [8,21].…”

Silicon Nanotubes Fabricated by Wet Chemical Etching of ZnO/Si Core–Shell Nanowires

“…Top-down techniques using lithography [ 13 , 14 , 15 ] and self-assembled nanosphere bead templates [ 16 , 17 , 18 ] have more recently been developed to fabricate SiNTs, but they require a complex manufacturing process, long processing time, or the use of noble metals. Other methods such as chemical etching [ 19 ] and electrochemical formation [ 20 ] cannot produce vertically aligned SiNTs, so they have limited applications.…”