Selective oxidation of CO in the presence of H2, H2O and CO2utilising Au/α-Fe2O3catalysts for use in fuel cells

Landon, Philip; Ferguson, J.; Solsona, Benjamín; Garcı́a, Tomás; Al-Sayari, S.A.; Carley, Albert Frederick; Herzing, Andrew A.; Kiely, Christopher J.; Makkee, Michiel; Moulijn, Jacob A.; Overweg, A.R.; Golunski, Stanislaw E.; Hutchings, Graham J.

doi:10.1039/b510762h

Cited by 92 publications

(57 citation statements)

References 36 publications

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“…The literature results vary greatly, so the nominal activities are normalized to the total amount of Au, with no adjustments made for Au particle size. We are aware of only two reports that achieve the 50/50 goal, both of which use low SVs and nominally dry feeds 7,14 . By controlling the amount of water added to the reaction (vide infra) and using higher SVs, we far surpassed the 50/50 goal, and did so at SVs 1-2 orders of magnitude larger than those in the literature ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The Au/Al 2 O 3 catalysts were more selective for PROX in our initial testing, so we focused additional studies on this system. Although the promotional effects of water in PROX have been reported 7,39 , there is no systematic study that seeks to control the activity and selectivity by adjusting the feed-water content. Herein we show that carefully controlling the feed-water content and space velocity (SV) leads to significant improvements in catalyst performance-far surpassing the 50/50 goal.…”

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confidence: 99%

“…They should be excellent PROX catalysts, but 20 years of research has produced very few catalysts capable of achieving the 50/50 goal (Fig. 1a) 7,14 . Numerous studies have searched for better catalysts, examining particle-size effects 12,15 , metal-oxide-support effects 16,17 , mixed metal oxides 15,18 and ordered mesoporous materials 19 .…”

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Controlling activity and selectivity using water in the Au-catalysed preferential oxidation of CO in H2

et al. 2016

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Section: Resultsmentioning

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Controlling activity and selectivity using water in the Au-catalysed preferential oxidation of CO in H2

et al. 2016

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“…For example for TiO 2 -supported catalysts, deposition precipitation is used where the TiO 2 is stirred in an aqueous solution of a gold salt and base is added to precipitate the gold, [78][79][80][81][82] whereas Fe 2 O 3 -supported catalysts are prepared by coprecipitation from an aqueous solution of gold and iron salts. [83][84][85] These methods tend to synthesize a very broad range of gold nano-structures and until recently particles in the 2-5 nm range were considered to be the active species in these catalysts. 85 However, transmission electron microscopy has advanced rapidly, especially with the introduction of C. u-VOPO 4 transforms to d-VOPO 4 when exposed to a variety of reactants at 400 C. A further transformation of d-VOPO 4 into a disordered material was observed when butane or acetic acid was added in the absence of oxygen.…”

Section: Designing Supported Gold and Gold Palladium Catalystsmentioning

confidence: 99%

Heterogeneous catalysts—discovery and design

Hutchings

2009

J. Mater. Chem.

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148

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Heterogeneous catalysis plays a key role in the manufacture of essential products in key areas of agriculture and pharmaceuticals, but also in the production of polymers and numerous essential materials. Our understanding of heterogeneous catalysts is advancing rapidly, especially by using the latest characterisation methods on these relatively complex effect materials. At the heart of these catalytic processes, both selective oxidation and hydrogenation play a key role. Both oxidation and hydrogenation exhibit similar requirements since often a partial reaction product is required, rather than the products of total hydrogenation or oxidation, in the latter case this being typically carbon dioxide and water. This Feature Article considers the approaches available for catalyst discovery and design for heterogeneous catalysts. Three catalysts are considered in detail, two exemplifying oxidation and the other selective hydrogenation. The design of vanadium phosphates for the selective oxidation of butane to maleic anhydride is described in terms of the search for advanced materials with superior activity. This is achieved through the synthesis of wholly amorphous vanadium phosphates. The design of supported gold and gold palladium alloy catalysts for the oxidation of carbon monoxide and the direct hydrogenation of oxygen to form hydrogen peroxide is described and the problems concerning selectivity control are discussed.

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Identifying Potential Active Species in Au/ZnO CO Oxidation Catalysts

Thomas

Edwards

et al. 2010

Microsc Microanal

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The low temperature oxidation of CO to CO 2 is a key reaction in the field of gold catalysis, not only because it represents Haruta's historic discovery of unexpected room temperature catalytic activity in nano-crystalline gold [1], but also because it is a commercially important reaction in fuel cell technology [2]. Gold supported on zinc oxide has been proven to exhibit good catalytic activity and stability for the CO oxidation reaction [3]. However numerous studies have as yet failed to conclusively reveal the identity of the catalytically active species in the Au/ZnO system [4].The aim of this work is to understand the nanostructure-performance relationships that exist for the Au/ZnO catalyst system. State-of-the-art electron microscopy techniques have been used to characterize a systematic series of Au/ZnO catalysts made by a simple co-precipitation method [3]. The set of catalysts were calcined over a range of different temperatures (i.e. dried at 110°C only, calcined at 200, 250, 300, 350, and 400°C) for a 4 hour-period. As shown in Fig. 1, the calcination temperature employed had a profound effect on the resultant catalytic performance, with those materials calcined at 250-300°C exhibiting the best CO conversion after 60 minutes on-line.Conventional bright field and phase contrast lattice imaging was effective for following the changes in ZnO grain-size and morphology over this temperature range, as shown in Fig. 2. In addition, it was possible to characterize the Au particle size distribution by these methods, provided that the metal particles were greater than 1nm in size. However the use of aberration corrected high angle annular dark field (HAADF) imaging [5] has now clearly shown that the nature of the gold distribution on ZnO is far more complex than previously imagined. So far, five distinct gold morphologies have been identified by STEM-HAADF to co-exist on these ZnO supports; namely (i) isolated Au atoms, (ii) sub-nm Au clusters, (iii) ordered monolayer rafts of Au atoms, (iv) linear stripes of Au and (v) epitaxial Au nano-particles greater than 1nm in diameter, as shown in Fig. 3. Interestingly, the estimated number fraction of these five distinct Au species is observed to vary with calcination temperature of the Au/ZnO catalyst. In this presentation, we will describe our efforts to deduce the relative catalytic activities of these various forms of supported gold by correlating the measured catalytic activity with catalyst nanostructure.

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Selective oxidation of CO in the presence of H₂, H₂O and CO₂utilising Au/α-Fe₂O₃catalysts for use in fuel cells

Cited by 92 publications

References 36 publications

Controlling activity and selectivity using water in the Au-catalysed preferential oxidation of CO in H2

Controlling activity and selectivity using water in the Au-catalysed preferential oxidation of CO in H2

Heterogeneous catalysts—discovery and design

Identifying Potential Active Species in Au/ZnO CO Oxidation Catalysts

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