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Fabrication and Characterization of Monodisperse Magnetic Porous Nickel Microspheres as Novel Catalysts.

Teng C, He J, Zhu L, Ren L, Chen J, Hong M, Wang Y - Nanoscale Res Lett (2015)

Bottom Line: The strategy involves impregnation of porous polymer microspheres with nickel precursors, calcination to remove the template, followed by thermal reduction.The unique porous nanostructured Ni microspheres possess catalytic activity and excellent recyclability, as demonstrated in the catalytic reduction of 4-nitrophenol to 4-aminophenol.The micropherical Ni catalysts could be easily separated either by an external magnetic field or by simple filtration.

View Article: PubMed Central - PubMed

Affiliation: Guangdong Provincial Key Laboratory of Nano-Micro Materials Research, School of Chemical Biology & Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.

ABSTRACT
A facile and efficient hard-templating strategy is reported for the preparation of porous nickel microspheres with excellent uniformity and strong magnetism. The strategy involves impregnation of porous polymer microspheres with nickel precursors, calcination to remove the template, followed by thermal reduction. The morphology, structure, and the property of the Ni microspheres were characterized by scanning electron microscopy, X-ray powder diffraction, N2 adsorption-desorption isotherms, thermogravimetric analysis, and magnetic hysteresis measurement. The obtained porous nickel microspheres were monodispersed with a particle size of 0.91 μm and crystallite size of 52 nm. Their saturation magnetization was much higher than that of Ni nanoparticles. The unique porous nanostructured Ni microspheres possess catalytic activity and excellent recyclability, as demonstrated in the catalytic reduction of 4-nitrophenol to 4-aminophenol. The micropherical Ni catalysts could be easily separated either by an external magnetic field or by simple filtration.

No MeSH data available.


Wide-angle powder XRD patterns of porous NiO microspheres and Ni microspheres reduced at 300 °C, 400 °C, and 500 °C. The violet lines show the standard diffractions of Ni (JCPDS No. 04–0850)
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Fig2: Wide-angle powder XRD patterns of porous NiO microspheres and Ni microspheres reduced at 300 °C, 400 °C, and 500 °C. The violet lines show the standard diffractions of Ni (JCPDS No. 04–0850)

Mentions: The crystalline phases and the crystallite sizes of the powders were confirmed by XRD measurements. Powder X-ray diffraction patterns revealed that the obtained porous NiO microspheres and Ni microspheres are all crystalline. The reflection peaks of NiO microspheres (shown in Fig. 2), indexed to (111), (200), (220), (311), and (222), can be well-assigned to the cubic phase of NiO (JCPDS card no. 47–1049). The average crystallite size of porous NiO microspheres, calculated based on the Williamson-Hall method, was ca. 29 nm, consistent with the SEM observation (Fig. 1f). Reduction of porous NiO microspheres at 300 °C converted most of the microspheres into Ni as the diffraction peaks of the face-centered cubic (fcc) phase of crystalline Ni (JCPDS card no. 04–0850) with 2θ of 44.4°, 51.7°, 76.3°, corresponding to (111), (200), and (220) planes of crystalline Ni, becoming highly intense. However, the NiO peaks were still present. Increasing the reduction temperature to 400 °C reduced the impurity amount of NiO, and only with a reduction temperature of 500 °C, no NiO could be seen. The crystallite size of pure Ni microspheres was calculated to be ca. 52 nm according to the Williamson-Hall method, larger than that of the NiO microspheres. Obviously, high-temperature reduction gave rise to extensive sintering due to surface condensation. The sintering behavior could also be seen in the SEM images. Although reduction at 500 °C was essential for converting NiO to Ni thoroughly, this high thermal reduction temperature created a slightly higher degree of crystallite growth and more bicontinous interpenetration of the metallic particles. Fortunately, the Ni microspheres were still separated showing smooth surfaces and clearly discernable spherical interfaces.Fig. 2


Fabrication and Characterization of Monodisperse Magnetic Porous Nickel Microspheres as Novel Catalysts.

Teng C, He J, Zhu L, Ren L, Chen J, Hong M, Wang Y - Nanoscale Res Lett (2015)

Wide-angle powder XRD patterns of porous NiO microspheres and Ni microspheres reduced at 300 °C, 400 °C, and 500 °C. The violet lines show the standard diffractions of Ni (JCPDS No. 04–0850)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4593984&req=5

Fig2: Wide-angle powder XRD patterns of porous NiO microspheres and Ni microspheres reduced at 300 °C, 400 °C, and 500 °C. The violet lines show the standard diffractions of Ni (JCPDS No. 04–0850)
Mentions: The crystalline phases and the crystallite sizes of the powders were confirmed by XRD measurements. Powder X-ray diffraction patterns revealed that the obtained porous NiO microspheres and Ni microspheres are all crystalline. The reflection peaks of NiO microspheres (shown in Fig. 2), indexed to (111), (200), (220), (311), and (222), can be well-assigned to the cubic phase of NiO (JCPDS card no. 47–1049). The average crystallite size of porous NiO microspheres, calculated based on the Williamson-Hall method, was ca. 29 nm, consistent with the SEM observation (Fig. 1f). Reduction of porous NiO microspheres at 300 °C converted most of the microspheres into Ni as the diffraction peaks of the face-centered cubic (fcc) phase of crystalline Ni (JCPDS card no. 04–0850) with 2θ of 44.4°, 51.7°, 76.3°, corresponding to (111), (200), and (220) planes of crystalline Ni, becoming highly intense. However, the NiO peaks were still present. Increasing the reduction temperature to 400 °C reduced the impurity amount of NiO, and only with a reduction temperature of 500 °C, no NiO could be seen. The crystallite size of pure Ni microspheres was calculated to be ca. 52 nm according to the Williamson-Hall method, larger than that of the NiO microspheres. Obviously, high-temperature reduction gave rise to extensive sintering due to surface condensation. The sintering behavior could also be seen in the SEM images. Although reduction at 500 °C was essential for converting NiO to Ni thoroughly, this high thermal reduction temperature created a slightly higher degree of crystallite growth and more bicontinous interpenetration of the metallic particles. Fortunately, the Ni microspheres were still separated showing smooth surfaces and clearly discernable spherical interfaces.Fig. 2

Bottom Line: The strategy involves impregnation of porous polymer microspheres with nickel precursors, calcination to remove the template, followed by thermal reduction.The unique porous nanostructured Ni microspheres possess catalytic activity and excellent recyclability, as demonstrated in the catalytic reduction of 4-nitrophenol to 4-aminophenol.The micropherical Ni catalysts could be easily separated either by an external magnetic field or by simple filtration.

View Article: PubMed Central - PubMed

Affiliation: Guangdong Provincial Key Laboratory of Nano-Micro Materials Research, School of Chemical Biology & Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.

ABSTRACT
A facile and efficient hard-templating strategy is reported for the preparation of porous nickel microspheres with excellent uniformity and strong magnetism. The strategy involves impregnation of porous polymer microspheres with nickel precursors, calcination to remove the template, followed by thermal reduction. The morphology, structure, and the property of the Ni microspheres were characterized by scanning electron microscopy, X-ray powder diffraction, N2 adsorption-desorption isotherms, thermogravimetric analysis, and magnetic hysteresis measurement. The obtained porous nickel microspheres were monodispersed with a particle size of 0.91 μm and crystallite size of 52 nm. Their saturation magnetization was much higher than that of Ni nanoparticles. The unique porous nanostructured Ni microspheres possess catalytic activity and excellent recyclability, as demonstrated in the catalytic reduction of 4-nitrophenol to 4-aminophenol. The micropherical Ni catalysts could be easily separated either by an external magnetic field or by simple filtration.

No MeSH data available.