CO oxidation over Au/ZrO2 catalysts: Activity, deactivation behavior, and reaction mechanism

Knell, A.J.; Barnickel, P.; Baiker, Alfons; Wokaun, Alexander

doi:10.1016/0021-9517(92)90159-f

Cited by 161 publications

(36 citation statements)

References 14 publications

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“…It may be noted that surface formates arising from the interaction between CO and surface hydroxy groups have also been proposed as reaction intermediates [73,146] .…”

Section: Haruta ' S Mechanism: Metal Gold Particlesmentioning

confidence: 99%

Gold Nanoparticles: Recent Advances in CO Oxidation

Louis

2007

Nanoparticles and Catalysis

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IntroductionThe oxidation of carbon monoxide at around room temperature is the most famous reaction known for gold catalysts. Haruta ' s group discovered in 1987 [1, 2] that gold is a unique catalyst for this reaction when gold metal particles are smaller than 5 nm and supported on oxides. Since then, extensive and intensive fundamental works have been published, and expanding new applications, from air purifi cation (gas masks, gas sensors, indoor air quality control) to hydrogen purifi cation for fuel cells (PROX, preferential selective oxidation of CO in the presence of H 2 ) have been developed.Gold is indeed active in carbon monoxide oxidation at a much lower temperature ( ≤ RT) than any platinum group metal [3] ( Fig. 15.1 ). The difference in reactivity can be due to the fact that Pt, Pd and Rh easily dissociate molecular oxygen at low temperature and bind strongly both atomic oxygen and CO. Tightly bound adsorbates have to overcome sizeable barriers to react, making the reaction rates signifi cant only at rather high temperatures [4] . On the contrary, on gold the reactants are loosely bound, but a higher binding energy of CO on gold nanoparticles than on bulk gold may provide suffi cient concentrations of CO on the surface for the reaction of oxidation to occur with negligible energy barriers. The main problem with this apparently simple reaction is that if CO is known to adsorb on low coordinated surface gold sites, the adsorption and activation of oxygen on gold particles is more puzzling (Section 15.4.3 ). The CO oxidation mechanism is not yet elucidated in spite of the huge number of papers published, and four main mechanisms have been suggested.High activity in CO oxidation when gold particles are smaller than 5 nm, and supported on reducible oxides, such as iron oxide or titania, led Haruta et al. [3, 5 -8] to propose the fi rst mechanism of CO oxidation (Fig. 15.2 ): the reaction takes place at the interface between the gold metal particle and the oxide support, i.e., between CO adsorbed on the gold particles and O 2 activated by the oxide support. Later, based on the assumption that metal cations could be located at the metalsupport interface, Bond and Thompson [9] proposed a mechanism rather similar, 475Nanoparticles and Catalysis. Edited by Didier Astruc

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“…It may be noted that surface formates arising from the interaction between CO and surface hydroxy groups have also been proposed as reaction intermediates [73,146] .…”

Section: Haruta ' S Mechanism: Metal Gold Particlesmentioning

confidence: 99%

Gold Nanoparticles: Recent Advances in CO Oxidation

Louis

2007

Nanoparticles and Catalysis

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“…35,36 In addition, tetragonal ZrO 2 is applied for catalysis and catalytic support for some gas phase reactions. 37,38 Chemical solution synthesis processes are often suitable for the production of conformal films and ceramic particles. These methods control grain size in the synthesis of tetragonal phase ZrO 2 .…”

Section: Forcespinning Of a Zirconia Shell Composition For Lmo Cathodmentioning

confidence: 99%

Surface engineering of electrospun fibers to optimize ion and electron transport in Li%2B battery cathodes.

Bell¹,

Missert²,

Leung³

et al. 2012

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This report documents research into the fabrication of Lithium Manganese Oxide (Spinel) (LMO) cathode material in the form of fibrous mats, the degradation process of this material in a battery electrolyte, the formation of core-shell coated fibers and the electrochemical properties of the active cathode core fiber. In practice, LMO experiences several degradation mechanisms ranging from capacity fading, the Jahn-Teller distortion phenomenon leading to dissolution in the electrolyte phase, and the formation of surface films by degradation of the electrolyte, and/or phase transitions at the surface to form Mn 2 O 3 . Density Functional Theory (DFT) was applied to model from first principles the interactions between the electrolyte and the surface leading to Mn ion dissolution. Thermodynamic values of solvation energy were calculated and related to the applied potential on the material during electrochemical cycling. Direct in situ observation of the degradation process was conducted on fiber structures using AFM and coin cell measurements, showing the rapid formation of theorized surface films. This provides the first direct evidence of processes occurring at the interface, such as dissolution of the active material, facet development, decomposition of the electrolyte to form a surface electrolyte interface (SEI) layer, or the 4 formation of Li alcoxides/carboxylates. Methods for fabricating fiber structures of LMO were researched using two techniques; electrospinning and forcespinning. Chemical precursors were evaluated and optimized to lead to polycrystalline, hollow fibers of LMO, as well as tetragonal zirconia fiber mats. Sol-gel chemistries for the synthesis of LMO and zirconia have been implemented to generate these fiber morphologies. Core-shell methods were attempted using both techniques, proving partial success and insight into the physics of coherent core-shell fibers.The knowledge developed in this program has increased understanding of the degradation mechanisms of the active energy storage material, and aided development of a protective interface which resists these processes while permitting rapid Li + transport, good e -conductivity, a stable interface, and prevention of the formation of a solid-electrolyte interphase (SEI) layer. 5

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“…The Au 4f7/2 peaks for samples 7, 8 and 9 centered at 84.7, 84.3 and 84.0 eV respectively show gold of partially oxidized state. As mentioned above, the catalyst precipitate precursor was Au(OH) 3 . When it was treated in oxygen at a relatively low temperature, gold retains certain oxidized state.…”

Section: Electrical Conductivity Measurementsmentioning

confidence: 99%

“…Owing to its chemical inertia and difficulty in dispersion on the supports, gold has long been regarded as a much less active catalyst than platinum group metals. However, recent studies [1][2][3] have clearly shown that gold is extraordinarily active for low-temperature CO oxidation. Supported gold catalysts, such as Au/TiO 2 , Au/MnO x , Au/ZnO, Au/Fe 2 O 3 , Au/Al 2 O 3 and Au/NiFe 2 O 4 , have been identified as promising catalysts used in chemical sensors [4][5][6] , sealed CO 2 lasers [7,8] and air purification devices [9,10] .…”

Section: Introductionmentioning

confidence: 99%

Catalytic performance and structural characterization of ferric oxide and its composite oxides supported gold catalysts for low-temperature CO oxidation

Zhang

Wang

2001

Sc. China Ser. B-Chem.

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The preparation and catalytic activity of ferric oxide and its composite oxides supported gold catalysts for low-temperature CO oxidation were investigated detailedly, and characterized extensively by XRD, XPS, TPR, EC and XAFS techniques. It was found that containing highly dispersed Au of partially oxidized state, these nano-structured oxides supported Au/Fe 2 O 3 and Au/NiFe 2 O 4 catalysts had higher low-temperature activities. The possible catalytic active center is the gold of partially oxidized state (Au ζ+ ). Owing to its chemical inertia and difficulty in dispersion on the supports, gold has long been regarded as a much less active catalyst than platinum group metals. However, recent studies [1][2][3] have clearly shown that gold is extraordinarily active for low-temperature CO oxidation. Supported gold catalysts, such as Au/TiO 2 , Au/MnO x , Au/ZnO, Au/Fe 2 O 3 , Au/Al 2 O 3 and Au/NiFe 2 O 4 , have been identified as promising catalysts used in chemical sensors [4][5][6] , sealed CO 2 lasers [7,8] and air purification devices [9,10] . Some of them are also employed for hydrogen elimination from CO 2 feed gas in urea synthesis [11,12] . These reaction data and applications indicate that Au and support interact synergistically, exhibiting high long-term CO oxidation activity near room temperature. The reason for the enhancement of the catalytic performance of these supported gold catalysts is thought to be related to the CO oxidation reaction mechanism and the structure of gold catalyst, such as gold particle size and chemical state. In order to clarify the mechanism of the catalytic oxidation of CO with O 2 , in situ IR, ESR and TPD-ITD techniques have been used, and some insight into the catalytic mechanism was obtained [13][14][15][16] . Furthermore, some supported gold catalysts such as Au/MnO x , Au/Fe 2 O 3 , Au/Al 2 O 3 , Au/Co 3 O 4 and Au/Mg(OH) 2 were examined using XPS, TEM, XAFS and Mössbauer surface characterization techniques [17][18][19][20][21][22][23] . Relatively little was understood about the possible catalytic active center [24]

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CO oxidation over Au/ZrO2 catalysts: Activity, deactivation behavior, and reaction mechanism

Cited by 161 publications

References 14 publications

Gold Nanoparticles: Recent Advances in CO Oxidation

Gold Nanoparticles: Recent Advances in CO Oxidation

Surface engineering of electrospun fibers to optimize ion and electron transport in Li%2B battery cathodes.

Catalytic performance and structural characterization of ferric oxide and its composite oxides supported gold catalysts for low-temperature CO oxidation

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