Why Au and Cu Are More Selective Than Pt for Preferential Oxidation of CO at Low Temperature

Kandoi, Shampa; Gokhale, Amit A.; Grabow, Lars C.; Dumesic, James A.; Mavrikakis, Manos

doi:10.1023/b:catl.0000016955.66476.44

Cited by 255 publications

(227 citation statements)

References 55 publications

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“…Addition of both CeO x and Li 2 O provides the best performing catalysts in selective CO oxidation. All three metals preferentially oxidize CO over H 2 at low temperatures in agreement with the DFT study of Kandoi [23]. Gold is the most active catalyst in CO oxidation with hydrogen present at low temperatures.…”

Section: Discussionsupporting

confidence: 83%

“…Recent studies have shown that also CuO mixed with ZnO [19] and CuO mixed with cerium oxide [20][21][22] are promising PROX catalysts. A DFT study [23] shows that gold and copper have a lower barrier for CO oxidation than for H 2 oxidation. Previously reported results show that ceria has a promoting effect on the activity of the Au/Al 2 O 3 catalyst in CO oxidation [13,24].…”

Section: Introductionmentioning

confidence: 99%

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A comparative study of the effect of addition of CeO x and Li2O on γ-Al2O3 supported copper, silver and gold catalysts in the preferential oxidation of CO

2007

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In the study described in this paper we deposited gold, silver and copper on c-Al 2 O 3 as nanoparticles (<4 nm) and investigated the behavior of these nanoparticles in the preferential oxidation of CO in presence of H 2 . In addition, the effect of addition of CeO x and/or Li 2 O was investigated. All the three metals show preferential oxidation of CO at low temperatures. The oxides added to Au/c-Al 2 O 3 , Ag/c-Al 2 O 3 and Cu/c-Al 2 O 3 improve the catalytic performance of the gold, silver and copper. Interesting and synergistic effects were observed when both the CeO x and Li 2 O were added. Possible mechanisms are proposed.

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Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

A comparative study of the effect of addition of CeO x and Li2O on γ-Al2O3 supported copper, silver and gold catalysts in the preferential oxidation of CO

2007

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“…Similarly to hydrogen activation, the dissociative adsorption of oxygen on ensembles of metallic gold atoms becomes more important at higher temperatures, reducing the possibility of CO + O 2 reaction, while in the same time the possibility of hydrogen oxidation becomes more important. This is ought to the higher energy barrier of the hydrogen oxidation reaction (O+H➝OH, H+OH➝H 2 O, OH+OH➝H 2 O+O) compared to that of CO oxidation (CO+O➝CO 2 ) (27). Thus, while CO oxidation is more favored at lower temperatures, at higher temperatures hydrogen oxidation becomes more important, explaining the drastic decrease of SCO activity and selectivity.…”

Section: Figurementioning

confidence: 99%

On the mechanism of selective CO oxidation on nanosized Auγ-Al2O3 catalysts

et al. 2006

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Nanometer-sized gold particles on oxide supports are efficient catalysts for the selective catalytic oxidation (SCO) of carbon monoxide under conditions compatible with the operation of PEM fuel cells. Nanosized Au/␥-Al 2 O 3 catalysts are able to oxidize CO between 20 and 70°C in an atmosphere of hydrogen combining high CO conversion and satisfactory selectivity to CO 2 (1). It is generally agreed that the catalytic activity of gold depends on the size of the gold particles, but the nature of support material, the preparation method, the activation procedure have also been suggested to play a key role (2). Sites at the gold support interface have also been claimed to be responsible for the activity in CO oxidation (3). Strain in the Au particles due to the mismatch of the lattices at the interface with the support (4) and the effect of low-coordinated sites and roughness (4) have also been suggested as important factors for high activity. The most important effect, concerning the catalytic activity of gold nanoparticles for low temperature oxidation of CO is related to the availability of many low-coordinated gold atoms on the small particles (5). Effects related to the interaction with the support may also contribute, but to a considerably smaller extent (5).CO oxidation over group VIII noble metals is the most studied catalytic reaction. However, selective oxidation of CO in hydrogen-rich conditions is not as well studied (6,7). CO (reactant) and CO 2 (product) sorption processes are fundamental elementary steps for SCO and moreover, the effect of hydrogen on their sorption over supported Au catalysts remains a subject of significant interest.Among the various supported Au catalysts, Au/Al 2 O 3 is perhaps one that has shown the widest variation for CO oxidation, ranging from being very inactive to practically as active as Au/TiO 2 (8). Compared to Au/␥-Al 2 O 3 , multicomponent gold-based catalysts also supported on ␥-Al 2 O 3 and combined with common metal oxides, such as: MnO x , MgO, FeO x (9,10) as well as gold catalysts supported on other materials such as Au/TiO 2 (11) and Au/FeO x (11,12) have been found to exhibit even more promising commercial performance for the SCO reaction. However, based on its simplicity, a well-studied Au/␥-Al 2 O 3 catalyst (1,9) has been utilized in the present work as model system, in order to gain fundamental information on the catalytic behaviour of gold nanoparticles and identify the active sites on Au/␥-Al 2 O 3 .In this paper, new findings which offer further information concerning the mechanism of CO preferential oxidation over nanosized Au are presented. The first finding concerns CO 2 formation in the absence of oxygen and hydrogen both in bare ␥-Al 2 O 3 as well as in Au/␥-Al 2 O 3 (called as CO decomposition). At high temperatures (>200 °C) in excess of H 2 , over the Au/␥-Al 2 O 3 catalyst, reversed water gas shift (RWGS) reaction results in CO 2 consumption towards CO and H 2 O formation. Finally, the kinetic measurements of the present work indicate that hydrog...

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“…This fact has led to the development of cheaper and more available active phases which show high activity and much higher selectivity to CO. The use of non-noble metal based catalysts, mainly copper catalysts, has received special attention due to the high selectivity in the CO-PROX reaction [15].…”

mentioning

confidence: 99%

The influence of promoters (Zr, La, Tb, Pr) on the catalytic performance of CuO-CeO2 systems for the preferential oxidation of CO in the presence of CO2 and H2O

et al. 2015

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CuO supported on CeO2 and Ce0.9X0.1O2, where X is Zr, La, Tb or Pr, were synthesized using nitrate precursors, giving rise ceria based materials with a small particle size which interact with CuO species generating a high amount of interfacial sites. The incorporation of cations to the ceria framework modifies the CeO2 lattice parameter, improving the redox behavior of the catalytic system. The catalysts were characterized by X-ray Diffraction (XRD), High-resolution Transmission Electron Microscopy (HRTEM), Raman spectroscopy, thermoprogrammed reduction with H2 (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The catalysts were tested in the preferential oxidation of CO under a H2-rich stream (CO-PROX), reaching conversion values higher than 95% between 115-140 ºC and being the catalyst with 6 wt.% of Cu supported on Ce0.9Zr0.1O2 (sample 6CUZRCE) the most active catalyst. The influence of the presence of CO2 and H2O was also studied simulating a PROX unit, taking place a decreasing of the catalytic activity due to the inhibitor effect both CO2 and H2O.

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Why Au and Cu Are More Selective Than Pt for Preferential Oxidation of CO at Low Temperature

Cited by 255 publications

References 55 publications

A comparative study of the effect of addition of CeO x and Li2O on γ-Al2O3 supported copper, silver and gold catalysts in the preferential oxidation of CO

A comparative study of the effect of addition of CeO x and Li2O on γ-Al2O3 supported copper, silver and gold catalysts in the preferential oxidation of CO

On the mechanism of selective CO oxidation on nanosized Auγ-Al2O3 catalysts

The influence of promoters (Zr, La, Tb, Pr) on the catalytic performance of CuO-CeO2 systems for the preferential oxidation of CO in the presence of CO2 and H2O

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