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Achieving nano-gold stability through rational design † † Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc01597b Click here for additional data file.

View Article: PubMed Central - PubMed

ABSTRACT

When Au is subdivided to the nanoscale its reactivity changes from an inert nature to one of incredible reactivity which is not replicated by other catalysts. When dispersed onto metal oxides such as TiO2, nano-Au has shown high reactivities for a multitude of reduction and oxidation reactions of industrial importance with potential and current uses such as, CO oxidation, NOx reduction, purification of hydrogen for fuel cells, water gas shift reactions, abatement of volatile organic compounds (VOC's) as well as pollution and emission control systems such as autocatalysts. However, many industrially important reactions and applications operate under harsh conditions where the catalyst is exposed to high temperatures and further needs to operate for extended periods of time. These conditions cause Au nanoparticle sintering whereby small, highly active clusters form large clusters which are catalytically inactive. For this reason, research into stabilizing Au nanoparticles has abounded with a goal of producing durable, thermally stable catalysts for industrial applications. Here we show a durable, thermally stable Au–TiO2 catalyst which has been developed by rational design. The catalyst exhibits a 3-dimensional, radially aligned nanorod structure, already locked into the thermodynamically stable polymorph, via a scalable and facile synthesis, with Au nanoparticles isolated on the support structure. As the Au nanoparticles are highly stable the new catalyst is able to maintain light-off for CO oxidation below 115 °C even after multiple cycles at 800 °C. This ability of the catalyst to resist multiple thermal cycles to high temperature while remaining active at low temperatures shows promise for various industrial applications. The thermal stability of the catalyst is investigated and characterized through morphological and structural studies.

No MeSH data available.


Related in: MedlinePlus

(A) SEM image (top left) of the catalyst after activation with the corresponding BSE image (top right) highlighting the Au nanoparticles as bright flashes. The images show the dispersion of Au nanoparticles which are isolated on the periphery of the structure after activation of the catalyst under hydrogen. HRTEM (bottom left and right) after activation of the catalyst. The images show the well-defined structure and distinct surface geometry of the Au nanoparticles at the tips of the nanorods as well as showing evidence of strong binding between the titania and the Au nanoparticles, (B) (Left) HAADF image of catalyst confirming the location of the Au (bright white spots) at the tips of the rods and showing the morphology of the RANR after in situ PXRD measurements under synthetic air. (Right) TEM image of the catalyst after in situ PXRD measurements for over 200 hours and holding at 810 °C for 5 hours confirmed minimal growth of the nano-Au.
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fig1: (A) SEM image (top left) of the catalyst after activation with the corresponding BSE image (top right) highlighting the Au nanoparticles as bright flashes. The images show the dispersion of Au nanoparticles which are isolated on the periphery of the structure after activation of the catalyst under hydrogen. HRTEM (bottom left and right) after activation of the catalyst. The images show the well-defined structure and distinct surface geometry of the Au nanoparticles at the tips of the nanorods as well as showing evidence of strong binding between the titania and the Au nanoparticles, (B) (Left) HAADF image of catalyst confirming the location of the Au (bright white spots) at the tips of the rods and showing the morphology of the RANR after in situ PXRD measurements under synthetic air. (Right) TEM image of the catalyst after in situ PXRD measurements for over 200 hours and holding at 810 °C for 5 hours confirmed minimal growth of the nano-Au.

Mentions: Phase pure titanium dioxide rutile nanorods with a specific morphology referred to as radially aligned nano rutile or RANR was prepared using a mild hydrothermal synthesis at ambient pressure. Alignment of the rutile nanorods was verified by electron diffraction, TEM (Fig. 1B) and in situ PXRD (Fig. S9†) with each nanorod having the same crystallographic orientation. The RANR consistently shows surface areas around 100 m2 g–1 providing relatively high usable surface area.


Achieving nano-gold stability through rational design † † Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc01597b Click here for additional data file.
(A) SEM image (top left) of the catalyst after activation with the corresponding BSE image (top right) highlighting the Au nanoparticles as bright flashes. The images show the dispersion of Au nanoparticles which are isolated on the periphery of the structure after activation of the catalyst under hydrogen. HRTEM (bottom left and right) after activation of the catalyst. The images show the well-defined structure and distinct surface geometry of the Au nanoparticles at the tips of the nanorods as well as showing evidence of strong binding between the titania and the Au nanoparticles, (B) (Left) HAADF image of catalyst confirming the location of the Au (bright white spots) at the tips of the rods and showing the morphology of the RANR after in situ PXRD measurements under synthetic air. (Right) TEM image of the catalyst after in situ PXRD measurements for over 200 hours and holding at 810 °C for 5 hours confirmed minimal growth of the nano-Au.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5134759&req=5

fig1: (A) SEM image (top left) of the catalyst after activation with the corresponding BSE image (top right) highlighting the Au nanoparticles as bright flashes. The images show the dispersion of Au nanoparticles which are isolated on the periphery of the structure after activation of the catalyst under hydrogen. HRTEM (bottom left and right) after activation of the catalyst. The images show the well-defined structure and distinct surface geometry of the Au nanoparticles at the tips of the nanorods as well as showing evidence of strong binding between the titania and the Au nanoparticles, (B) (Left) HAADF image of catalyst confirming the location of the Au (bright white spots) at the tips of the rods and showing the morphology of the RANR after in situ PXRD measurements under synthetic air. (Right) TEM image of the catalyst after in situ PXRD measurements for over 200 hours and holding at 810 °C for 5 hours confirmed minimal growth of the nano-Au.
Mentions: Phase pure titanium dioxide rutile nanorods with a specific morphology referred to as radially aligned nano rutile or RANR was prepared using a mild hydrothermal synthesis at ambient pressure. Alignment of the rutile nanorods was verified by electron diffraction, TEM (Fig. 1B) and in situ PXRD (Fig. S9†) with each nanorod having the same crystallographic orientation. The RANR consistently shows surface areas around 100 m2 g–1 providing relatively high usable surface area.

View Article: PubMed Central - PubMed

ABSTRACT

When Au is subdivided to the nanoscale its reactivity changes from an inert nature to one of incredible reactivity which is not replicated by other catalysts. When dispersed onto metal oxides such as TiO2, nano-Au has shown high reactivities for a multitude of reduction and oxidation reactions of industrial importance with potential and current uses such as, CO oxidation, NOx reduction, purification of hydrogen for fuel cells, water gas shift reactions, abatement of volatile organic compounds (VOC's) as well as pollution and emission control systems such as autocatalysts. However, many industrially important reactions and applications operate under harsh conditions where the catalyst is exposed to high temperatures and further needs to operate for extended periods of time. These conditions cause Au nanoparticle sintering whereby small, highly active clusters form large clusters which are catalytically inactive. For this reason, research into stabilizing Au nanoparticles has abounded with a goal of producing durable, thermally stable catalysts for industrial applications. Here we show a durable, thermally stable Au–TiO2 catalyst which has been developed by rational design. The catalyst exhibits a 3-dimensional, radially aligned nanorod structure, already locked into the thermodynamically stable polymorph, via a scalable and facile synthesis, with Au nanoparticles isolated on the support structure. As the Au nanoparticles are highly stable the new catalyst is able to maintain light-off for CO oxidation below 115 °C even after multiple cycles at 800 °C. This ability of the catalyst to resist multiple thermal cycles to high temperature while remaining active at low temperatures shows promise for various industrial applications. The thermal stability of the catalyst is investigated and characterized through morphological and structural studies.

No MeSH data available.


Related in: MedlinePlus