Dopants adsorbed as single atoms prevent degradation of catalysts

Wang, Sanwu; Borisevich, Albina Y.; Rashkeev, Sergey N.; Glazoff, Michael V.; Sohlberg, Karl; Pennycook, Stephen J.; Pantelides, Sokrates T.

doi:10.1038/nmat1077

Cited by 217 publications

(169 citation statements)

References 28 publications

Supporting

Mentioning

163

Contrasting

Unclassified

Order By: Relevance

“…7a). Integration of this structural relationship with the g-alumina structure was achieved by placing the La atom into the four-fold hollow site provided by an Al 3 þ vacancy 15 , and by replacing an adjacent penta-coordinated Al 3 þ ion (ionic radius (VI octahedral) 0.53 Å) with a Pd 2 þ ion (ionic radius (IV square planar) 0.64 Å) 25 (Fig. 7b).…”

Section: Resultsmentioning

confidence: 99%

“…Using X-ray photoelectron spectroscopy (XPS), Haack et al 14 determined that for La/Al ratios o0. 15, La is probably present as a dispersed, low-coordinated La 3 þ phase, rather than as La 2 O 3 . Lanthanum oxide has been routinely added to g-alumina in automobile catalysts since these discoveries, but the location of the La 3 þ was somewhat of a mystery until the advent of aberration-corrected (AC) electron microscopes, in conjunction with DFT calculations.…”

mentioning

confidence: 99%

“…Lanthanum oxide has been routinely added to g-alumina in automobile catalysts since these discoveries, but the location of the La 3 þ was somewhat of a mystery until the advent of aberration-corrected (AC) electron microscopes, in conjunction with DFT calculations. It was shown by Wang et al 15 that atomically dispersed La 3 þ is present on the g-alumina surface, settling into four-fold hollow, Al 3 þ vacancy sites. These surface La 3 þ ions appear to pin the oxygen substructure, hindering the reconstructive transformation from the fcc (abcabcy) arrangement to the hcp (hexagonally close packed) (abababy) packing of the corundum structure.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

et al. 2014

View full text Add to dashboard Cite

Catalysis by single isolated atoms of precious metals has attracted much recent interest, as it promises the ultimate in atom efficiency. Most previous reports are on reducible oxide supports. Here we show that isolated palladium atoms can be catalytically active on industrially relevant g-alumina supports. The addition of lanthanum oxide to the alumina, long known for its ability to improve alumina stability, is found to also help in the stabilization of isolated palladium atoms. Aberration-corrected scanning transmission electron microscopy and operando X-ray absorption spectroscopy confirm the presence of intermingled palladium and lanthanum on the g-alumina surface. Carbon monoxide oxidation reactivity measurements show onset of catalytic activity at 40°C. The catalyst activity can be regenerated by oxidation at 700°C in air. The high-temperature stability and regenerability of these ionic palladium species make this catalyst system of potential interest for low-temperature exhaust treatment catalysts.

show abstract

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

et al. 2014

View full text Add to dashboard Cite

show abstract

“…6,7 On the other hand, ␥-Al 2 O 3 is exceedingly valuable in catalysis. 8 For many of these applications, it is imperative to form thin films. It is a common practice to synthesize thermodynamically stable ␣-Al 2 O 3 at temperatures Ն1000°C using chemical vapor deposition, 9 but this high thermal load restricts the range of possible substrates and hence hinders widespread applications.…”

mentioning

confidence: 99%

Ab initio molecular dynamics of Al irradiation-induced processes during Al2O3 growth

Mušić

Nahif

Sarakinos

et al. 2011

Applied Physics Letters

View full text Add to dashboard Cite

Al bombardment induced structural changes in α-Al2O3 (R-3c) and γ-Al2O3 (Fd-3m) were studied using ab initio molecular dynamics. Diffusion and irradiation damage occur for both polymorphs in the kinetic energy range from 3.5 to 40 eV. However, for γ-Al2O3(001) subplantation of impinging Al causes significantly larger irradiation damage and hence larger mobility as compared to α-Al2O3. Consequently, fast diffusion along γ-Al2O3(001) gives rise to preferential α-Al2O3(0001) growth, which is consistent with published structure evolution experiments.

show abstract

“…In Scanning Transmission Electron Microscopy (STEM), the enhanced sensitivity and resolution have enabled the detection of single atoms [1] and the resolving of sub-Ångstrom spacings [2] on an almost routine basis. Additionally, there have been a number of unexpected benefits from aberration correction.…”

mentioning

confidence: 99%

Imaging of Materials through Aberration Corrected STEM

Lupini

Veith

Dudney

et al. 2005

MAM

View full text Add to dashboard Cite

Aberration correction has caused something of a revolution in electron microscopy. In Scanning Transmission Electron Microscopy (STEM), the enhanced sensitivity and resolution have enabled the detection of single atoms [1] and the resolving of sub-Ångstrom spacings [2] on an almost routine basis. Additionally, there have been a number of unexpected benefits from aberration correction. Firstly, because the Rayleigh diffraction limit is given by: 0.61λ/θ, in order to take advantage of the reduced aberrations, the objective aperture θ must be made larger. Thus aberration correction not only allows a smaller probe size, but also admits the possibility of increased current inside that smaller probe. Secondly, this increased aperture size allows a new technique for 3-dimensional imaging [3,4], similar to optical confocal microscopy. For a diffraction limited system, in the absence of aberrations, the depth of field is commonly defined [5] as: λ/θ 2 . This is the 80% of maximum on axis criteria, so in practice the depth resolution is a little worse than this. Even in the presence of aberrations, we would expect this result to be approximately true, because the aperture is normally chosen so that it is just smaller than the angle at which the aberrations become significant.Three-dimensional imaging is important because all real samples are three-dimensional, yet most microscope images are two-dimensional representations of a sample and it is not always possible to reconstruct a three-dimensional model from these images. In addition, the limited depth of focus will become even more relevant with improvements in corrector design, because it is already comparable to specimen thickness. Thus for many samples, the variations in height are far larger than the depth of field in a C s -corrected system. So this is not just a way to extract new information; it will become essential to consider the reduced depth of focus in order to interpret images from any non-flat sample. Similarly, for the case of single atoms buried in an amorphous substrate, it has been shown [4] that the single atoms are not necessarily visible unless the beam is focused within the sample. Thus, even where three-dimensional information is not explicitly required, it may be essential to use this technique in order to extract the correct distribution of dopants or impurities. In aligned crystals, the electrons are attracted to the columns of atoms, which is sometimes known as channeling, so there the behavior is more complicated [6]. This also has implications for tomography. If the depth of focus is too small, then the images at different tilts are not simple projections and the approximations used to derive the tomographic reconstruction are no longer valid, in which case tomography will necessarily involve some form of deconvolution.By reciprocity, the bright field (BF) STEM image is equivalent to the BF TEM image. The main reason that the STEM is not more widely used for BF imaging is that the efficiency is very low. Only a small fraction of the electron...

show abstract

Dopants adsorbed as single atoms prevent degradation of catalysts

Cited by 217 publications

References 28 publications

Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

Ab initio molecular dynamics of Al irradiation-induced processes during Al2O3 growth

Imaging of Materials through Aberration Corrected STEM

Contact Info

Product

Resources

About