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Schumacher, B.; Plzak, V.; Kinne, M.; Behm, R. Jürgen

doi:10.1023/a:1024731812974

Cited by 163 publications

(146 citation statements)

References 15 publications

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“…6) and agree with DRIFTS measurements showing formation and build-up of carbonates, carboxylates, hydroxycarbonyls/formates, and bicarbonates on Au/TiO 2 during CO oxidation [6,9,18,19,25]. The point whether the carbonates reside on the gold [19], on the support [9,18,27], on the Au-TiO 2 border [6], or on both the Au and the support [28] is still in debate. Our SIMS data demonstrating an intense emission of molecular ions…”

Section:  Ohsupporting

confidence: 81%

“…Deactivation of the catalyst was suggested to occur due to reduction of oxidized gold species (which were claimed to be the most active sites for CO oxidation) to metallic gold [3,4], sintering of Au nanoparticles (irreversible) [6,15,18], dehydroxylation of the support during the reaction (assuming that OH groups were involved in the oxidation pathway) [23,24], and accumulation of carbonate-like species (carbonate  2 3 CO , formate  2 HCO and carboxylate O-CO groups) at the active sites [6,9,19,25,27,28]. In our work, some sintering, dehydroxylation and build-up of surface carbonate-like species occurred in the catalyst (DP1) already after 1 h on stream, although no deactivation was observed ( Fig.…”

Section:  Ohmentioning

confidence: 99%

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XPS/ToF-SIMS Characterization of TiO$_{2}$ Supported Au Nanoparticles: Effect of Catalytic CO Oxidation

Chenakin¹,

Kruse²,

Vasylyev³

et al. 2016

Metallofiz. Noveishie Tekhnol.

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X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) are employed for a comparative study of the surface composition and electronic structure of an Au/TiO 2 catalyst in the asprepared state and after using it in the reaction of CO oxidation at room temperature. As found, the reaction-induced changes in the morphology of Au nanoparticles related to their agglomeration are accompanied by modification of the electronic state of the catalyst via an enhanced electron transfer to the gold atoms that shows up as an additional negative shift of the Au 4f spectrum and its distortion. The catalytic reaction of CO oxidation results in the loss of hydroxyl groups and accumulation on the support surface of various carbon-containing species with the leading formation of carbonate and bicarbonate groups, which increases with time on stream. The role of these factors in deactivation of the catalyst is discussed.За допомогою рентґенівської фотоелектронної спектроскопії (РФЕС) та часопролітної вторинно-іонної мас-спектрометрії (ЧП-ВІМС) проведено порівняльне дослідження складу поверхні й електронної структури ката-лізатора Au/TiO 2 у свіжоприготованому стані та після його використання у реакції окиснення CO за кімнатної температури. Встановлено, що інду-ковані каталітичною реакцією зміни у морфології наночастинок Au, які спричинені їхньою аґломерацією, супроводжувалися модифікуванням електронного стану каталізатора завдяки посиленому перенесенню елек-тронів на атоми золота, що проявлялося як додатковий неґативний зсув РФЕ-спектра Au 4f і його спотворення. Каталітична реакція окиснення CO призводила до втрати гідроксильних груп та накопичення на поверхні підкладки різних вуглецевмісних функціональних груп з переважним С помощью рентгеновской фотоэлектронной спектроскопии (РФЭС) и времяпролётной вторично-ионной масс-спектрометрии (ВП-ВИМС) про-ведено сравнительное исследование состава поверхности и электронной структуры катализатора Au/TiO 2 в свежеприготовленном состоянии и по-сле его использования в реакции окисления CO при комнатной темпера-туре. Установлено, что индуцированные каталитической реакцией изме-нения в морфологии наночастиц Au, вызванные их агломерацией, сопро-вождались модификацией электронного состояния катализатора путём усиленного переноса электронов на атомы золота, что проявлялось в виде дополнительного отрицательного сдвига РФЭ-спектра Au 4f и его иска-жения. Каталитическая реакция окисления CO приводила к потере гид-роксильных групп и накоплению на поверхности подложки различных углеродсодержащих функциональных групп с преимущественным фор-мированием карбонатов и бикарбонатов, которое усиливалось с течением времени реакции. Обсуждается роль этих факторов в деактивации ката-лизатора.

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Section:  Ohsupporting

confidence: 81%

Section:  Ohmentioning

confidence: 99%

XPS/ToF-SIMS Characterization of TiO$_{2}$ Supported Au Nanoparticles: Effect of Catalytic CO Oxidation

Chenakin¹,

Kruse²,

Vasylyev³

et al. 2016

Metallofiz. Noveishie Tekhnol.

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“…Still others consider carbonates as catalyst poisons, acting according to one of two postulated poisoning mechanisms. The first attributes poisoning to carbonates formation on Au surfaces limiting CO adsorption on the catalysts [81]. The second stipulates that oxygen activation occurs at nanoparticle perimeter sites located at the metal-support interface.…”

Section: Loss Of Active Sites and Carbonates Buildupmentioning

confidence: 99%

CO oxidation over Au/TiO2 catalyst: Pretreatment effects, catalyst deactivation, and carbonates production

Lopez

Powell

Panthi

et al. 2013

Journal of Catalysis

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a b s t r a c tA commercially available Au/TiO 2 catalyst was subjected to a variety of thermal treatments in order to understand how variations in catalyst pretreatment procedures might affect CO oxidation catalysis. Catalytic activity was found to be inversely correlated to the temperature of the pretreatment. Infrared spectroscopy of adsorbed CO experiments, followed by a Temkin analysis of the data, indicated that the thermal treatments caused essentially no changes to the electronics of the Au particles; this, and a series of catalysis control experiments, and previous transmission electron microscopy (TEM) studies ruled out particle growth as a contributing factor to the activity loss. Fourier transform infrared (FTIR) spectroscopy showed that pretreating the catalyst results in water desorption from the surface, but the observable water loss was similar for all the treatments and could not be correlated with catalytic activity. A Michaelis-Menten kinetic treatment indicated that the main reason for deactivation is a loss in the number of active sites with little changes in their intrinsic activity. In situ FTIR experiments during CO oxidation showed extensive buildup of carbonate-like surface species when the pretreated catalysts were contacted with the feed gas. A semi-quantitative infrared spectroscopy method was developed for comparing the amount of carbonates present on each catalyst; results from these experiments showed a strong correlation between the steady-state catalytic activity and amount of surface carbonates generated during the initial moments of catalysis. Further, this experimental protocol was used to show that the carbonates reside on the titania support rather than on the Au, as there was no evidence that they poison Au-CO binding sites. The role of the carbonates in the reaction scheme, their potential role in catalyst deactivation, and the role of surface hydroxyls and water are discussed.

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“…More and more groups [11, 21, 42, 47 -50] are now aware of these problems, and perform the preparation in the dark, dry the samples at low temperature ( ≤ 373 K under vacuum or at RT) and store them free of light and air or water. As mentioned in Section 15.2 , it is very important to eliminate the chlorides before thermal treatment and possibly also sodium when NaOH or Na 2 CO 3 are used for the preparations [25,49] .…”

Section: Preliminary Remarksmentioning

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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Cited by 163 publications

References 15 publications

XPS/ToF-SIMS Characterization of TiO$_{2}$ Supported Au Nanoparticles: Effect of Catalytic CO Oxidation

XPS/ToF-SIMS Characterization of TiO$_{2}$ Supported Au Nanoparticles: Effect of Catalytic CO Oxidation

CO oxidation over Au/TiO2 catalyst: Pretreatment effects, catalyst deactivation, and carbonates production

Gold Nanoparticles: Recent Advances in CO Oxidation

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