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Gold nanoparticles supported on magnesium oxide for CO oxidation.

Carabineiro SA, Bogdanchikova N, Pestryakov A, Tavares PB, Fernandes LS, Figueiredo JL - Nanoscale Res Lett (2011)

Bottom Line: Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction.CO oxidation was used as a test reaction to compare the catalytic activity.This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratório de Catálise e Materiais, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, 4200-465 Porto, Portugal. scarabin@fe.up.pt.

ABSTRACT
Au was loaded (1 wt%) on a commercial MgO support by three different methods: double impregnation, liquid-phase reductive deposition and ultrasonication. Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Upon loading with Au, MgO changed into Mg(OH)2 (the hydroxide was most likely formed by reaction with water, in which the gold precursor was dissolved). The size range for gold nanoparticles was 2-12 nm for the DIM method and 3-15 nm for LPRD and US. The average size of gold particles was 5.4 nm for DIM and larger than 6.5 for the other methods. CO oxidation was used as a test reaction to compare the catalytic activity. The best results were obtained with the DIM method, followed by LPRD and US. This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

No MeSH data available.


X-ray diffraction spectra of commercial MgO, pure (thin line) and loaded with 1% Au wt (thicker line) by DIM, with phases and respective crystal planes (Miller indexes) identified.
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Figure 1: X-ray diffraction spectra of commercial MgO, pure (thin line) and loaded with 1% Au wt (thicker line) by DIM, with phases and respective crystal planes (Miller indexes) identified.

Mentions: Figure 1 shows the XRD spectra of the oxide supports alone, and loaded with 1 wt% Au by DIM. The identified phase for the unloaded material is the respective oxide (cubic, Fm-3m, 01-078-0430), with a crystallite size of 42 nm; however, when gold is loaded, a new Mg(OH)2 phase (hexagonal, P-3m1, 01-076-0667) was formed (Figure 1). 99% of this hydroxide phase was detected along with 1% MgO. It was not possible to calculate the particle size of the Mg(OH)2 phase due to interstratification of hydrated phases, as also found by other authors [40], which makes it very difficult to simulate the spectra, so the results obtained (in this case approximately 25 nm) are not reliable. The hydroxide is most likely formed by reaction with water, in which the gold precursor is dissolved (MgO + H2O → Mg(OH)2). Similar results were obtained for the other loading methods.


Gold nanoparticles supported on magnesium oxide for CO oxidation.

Carabineiro SA, Bogdanchikova N, Pestryakov A, Tavares PB, Fernandes LS, Figueiredo JL - Nanoscale Res Lett (2011)

X-ray diffraction spectra of commercial MgO, pure (thin line) and loaded with 1% Au wt (thicker line) by DIM, with phases and respective crystal planes (Miller indexes) identified.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211853&req=5

Figure 1: X-ray diffraction spectra of commercial MgO, pure (thin line) and loaded with 1% Au wt (thicker line) by DIM, with phases and respective crystal planes (Miller indexes) identified.
Mentions: Figure 1 shows the XRD spectra of the oxide supports alone, and loaded with 1 wt% Au by DIM. The identified phase for the unloaded material is the respective oxide (cubic, Fm-3m, 01-078-0430), with a crystallite size of 42 nm; however, when gold is loaded, a new Mg(OH)2 phase (hexagonal, P-3m1, 01-076-0667) was formed (Figure 1). 99% of this hydroxide phase was detected along with 1% MgO. It was not possible to calculate the particle size of the Mg(OH)2 phase due to interstratification of hydrated phases, as also found by other authors [40], which makes it very difficult to simulate the spectra, so the results obtained (in this case approximately 25 nm) are not reliable. The hydroxide is most likely formed by reaction with water, in which the gold precursor is dissolved (MgO + H2O → Mg(OH)2). Similar results were obtained for the other loading methods.

Bottom Line: Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction.CO oxidation was used as a test reaction to compare the catalytic activity.This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratório de Catálise e Materiais, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, 4200-465 Porto, Portugal. scarabin@fe.up.pt.

ABSTRACT
Au was loaded (1 wt%) on a commercial MgO support by three different methods: double impregnation, liquid-phase reductive deposition and ultrasonication. Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Upon loading with Au, MgO changed into Mg(OH)2 (the hydroxide was most likely formed by reaction with water, in which the gold precursor was dissolved). The size range for gold nanoparticles was 2-12 nm for the DIM method and 3-15 nm for LPRD and US. The average size of gold particles was 5.4 nm for DIM and larger than 6.5 for the other methods. CO oxidation was used as a test reaction to compare the catalytic activity. The best results were obtained with the DIM method, followed by LPRD and US. This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

No MeSH data available.