Mechanistic investigation on salt-mediated formation of free-standing Co3O4 nanocubes at 95°C

Rong Xu; Chun Zeng

doi:10.1021/jp021094x

Mechanistic investigation on salt-mediated formation of free-standing Co₃O₄ nanocubes at 95°C

Rong Xu, Chun Zeng^*

^*Corresponding author for this work

National University of Singapore

Research output: Contribution to journal › Article › peer-review

170 Citations (Scopus)

Abstract

The transformation process of various cobalt hydroxide and hydroxide nitrate into final free-standing Co₃O₄ nanocubes with a uniform size of ca. 47 nm has been investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and high-resolution transmission electron microscopy (HRTEM) methods. It is found that during their sequential oxidation under air bubbling at 95°C, β-Co(OH)₂ and Co^II(OH)_2-x(NO₃)_x· NH₂O solid phases are gradually oxidized to a mixture of Co^II_1-xCo^III_x(OH)₂ (NO₃)_x·nH₂O and Co₃O₄ in high concentration nitrate salt (e.g., NaNO₃) solution, through which the single-phase Co₃O₄ nanocubes have been formed with a prolonged oxidation. With the mediation of NaNO₃ salt in synthesis, formation of perfectly faceted Co₃O₄ nanocubes can be attributed to a lowering in O₂ solubility and creation of salt-(solvent)_n diffusion boundary on the surfaces, which retards the cobalt oxidation and alters the normal interfacial growth under nonsalted conditions.

Original language	English
Pages (from-to)	926-930
Number of pages	5
Journal	Journal of Physical Chemistry B
Volume	107
Issue number	4
DOIs	https://doi.org/10.1021/jp021094x
Publication status	Published - Jan 30 2003
Externally published	Yes

ASJC Scopus Subject Areas

Physical and Theoretical Chemistry
Surfaces, Coatings and Films
Materials Chemistry

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title = "Mechanistic investigation on salt-mediated formation of free-standing Co3O4 nanocubes at 95°C",

abstract = "The transformation process of various cobalt hydroxide and hydroxide nitrate into final free-standing Co3O4 nanocubes with a uniform size of ca. 47 nm has been investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and high-resolution transmission electron microscopy (HRTEM) methods. It is found that during their sequential oxidation under air bubbling at 95°C, β-Co(OH)2 and CoII(OH)2-x(NO3)x· NH2O solid phases are gradually oxidized to a mixture of CoII1-xCoIIIx(OH)2 (NO3)x·nH2O and Co3O4 in high concentration nitrate salt (e.g., NaNO3) solution, through which the single-phase Co3O4 nanocubes have been formed with a prolonged oxidation. With the mediation of NaNO3 salt in synthesis, formation of perfectly faceted Co3O4 nanocubes can be attributed to a lowering in O2 solubility and creation of salt-(solvent)n diffusion boundary on the surfaces, which retards the cobalt oxidation and alters the normal interfacial growth under nonsalted conditions.",

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doi = "10.1021/jp021094x",

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N2 - The transformation process of various cobalt hydroxide and hydroxide nitrate into final free-standing Co3O4 nanocubes with a uniform size of ca. 47 nm has been investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and high-resolution transmission electron microscopy (HRTEM) methods. It is found that during their sequential oxidation under air bubbling at 95°C, β-Co(OH)2 and CoII(OH)2-x(NO3)x· NH2O solid phases are gradually oxidized to a mixture of CoII1-xCoIIIx(OH)2 (NO3)x·nH2O and Co3O4 in high concentration nitrate salt (e.g., NaNO3) solution, through which the single-phase Co3O4 nanocubes have been formed with a prolonged oxidation. With the mediation of NaNO3 salt in synthesis, formation of perfectly faceted Co3O4 nanocubes can be attributed to a lowering in O2 solubility and creation of salt-(solvent)n diffusion boundary on the surfaces, which retards the cobalt oxidation and alters the normal interfacial growth under nonsalted conditions.

AB - The transformation process of various cobalt hydroxide and hydroxide nitrate into final free-standing Co3O4 nanocubes with a uniform size of ca. 47 nm has been investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and high-resolution transmission electron microscopy (HRTEM) methods. It is found that during their sequential oxidation under air bubbling at 95°C, β-Co(OH)2 and CoII(OH)2-x(NO3)x· NH2O solid phases are gradually oxidized to a mixture of CoII1-xCoIIIx(OH)2 (NO3)x·nH2O and Co3O4 in high concentration nitrate salt (e.g., NaNO3) solution, through which the single-phase Co3O4 nanocubes have been formed with a prolonged oxidation. With the mediation of NaNO3 salt in synthesis, formation of perfectly faceted Co3O4 nanocubes can be attributed to a lowering in O2 solubility and creation of salt-(solvent)n diffusion boundary on the surfaces, which retards the cobalt oxidation and alters the normal interfacial growth under nonsalted conditions.

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Mechanistic investigation on salt-mediated formation of free-standing Co₃O₄ nanocubes at 95°C

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