Revealing the Atomic Restructuring of Pt–Co Nanoparticles

Xin, Huolin L.; Alayoǧlu, Selim; Tao, Runzhe; Genç, Arda; Wang, Chongmin; Kovařík, Libor; Stach, Eric A.; Wang, Lin‐Wang; Salmerón, Miquel; Somorjai, Gábor A.; Zheng, Haimei

doi:10.1021/nl500553a

Cited by 169 publications

(177 citation statements)

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“…Likewise, annular dark field images obtained in 100 mTorr H 2 , the same partial pressure as in APXPS studies, for individual nanoparticles (Fig. 11), showed bright surface layers and dark subsurface shells, indicating the enrichment of higher Z Pt atoms in the surface regions and Co atoms in the subsurface regions [95,99]. Hence, TEM agreed with the APXPS results pointing to core/shell restructuring and Pt surface segregation of once alloyed nanoparticles in H 2 atmospheres.…”

Section: The Role Of Nobler Metal In Co-based Bimetallicsupporting

confidence: 78%

“…Note that Co shuffled back into the alloy particle as compared to the segregated particle in Fig. 7c [modified with permission from Xin et al [99] aldehydes chemisorbed on Pt sites with their C=C double bonds lying parallel to the surface while C=O bonds were located upright and away from the surface. This bonding configuration led to selective hydrogenation of the C=C double bond and desorption of the saturated aldehyde, as illustrated in Fig.…”

Section: The Role Of Nobler Metal In Co-based Bimetallicmentioning

confidence: 99%

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Nanocatalysis II: In Situ Surface Probes of Nano-Catalysts and Correlative Structure–Reactivity Studies

Alayoǧlu

Somorjai

2014

Catal Lett

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Model nano-catalysts with monodisperse particle sizes and architectures are essential for a fundamental understanding of surface property dynamics during catalytic reactions. Surface tools and techniques, when conducted under catalytically relevant temperature and pressure conditions, render possible measurements of dynamic surface properties such as oxidation state, composition, coordination, and bonding. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy with purposely built in situ reaction cells and ambient pressure X-ray photoelectron spectroscopy (APXPS) provide (near) surface sensitive and chemical specific information on the oxidation states of metal and oxide (co-)catalysts as well as adsorbent functional elements such C, O and N under reactive gas atmospheres and even liquid environments. Likewise, sum frequency generation (SFG) vibrational spectroscopy with in situ reaction cells helps uncover the bonding geometry and configuration of the topmost surface again under conditions pertinent to catalysis. Furthermore, the local dynamics in the nanoscale and on the single particle level are revealed by environmental transmission electron microscopy (ETEM) and the spectro-microscopy techniques equipped within. A correlative approach, where an array of these in situ tools and techniques were conducted in parallel with catalytic measurements, was employed to gain molecular insight into some of the modern scientific challenges in heterogeneous catalysis.Several case examples of this correlative approach are presented here. The CO oxidation reaction over hybrid nano-catalysts of Pt nanoparticles (NPs) with various mesoporous metal oxides such as Co 3 O 4 , MnO 2 and CeO 2 was explored in relation to bifunctional catalysis and interfacial charge transfer chemistry by using in situ NEXAFS spectroscopy. Likewise, bimetallic CoPt and PtSn nanoparticle catalysts supported on silica were investigated by using a combination of in situ NEXAFS spectroscopy and APXPS. Next, CO 2 hydrogenation was carried out over bimetallic CoPt/SiO 2 and Co/TiO 2 hybrid nano-catalysts. In this case, in situ NEXAFS spectroscopy, APXPS, and ETEM indicated severe, yet reversible, surface restructuring that involved hydrogen atom spillover. Finally, *2 nm Pt NPs were investigated using in situ SFG to study hydrogenation and hydrogenative isomerization reactions. Specifically, SFG indicated that the hydrogenation of furfural and crotonaldehyde proceed by interfacial hydrogen atom spillover from TiO 2 , while the hydrogenative isomerization of methylcyclopentane (MCP) proceeds by spillover and surface diffusion of cyclohexene over mesoporous zeolites. These studies unequivocally indicated the presence of a particular reaction channel that involved one way flow of charged (i.e. electrons or protons) or neutral species (i.e. reactants) at a broadly defined interface between metals and oxides. In addition to these case studies, experimental approaches employing capillary flow micro-reactors are discussed in relation toward t...

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Section: The Role Of Nobler Metal In Co-based Bimetallicsupporting

confidence: 78%

Section: The Role Of Nobler Metal In Co-based Bimetallicmentioning

confidence: 99%

Nanocatalysis II: In Situ Surface Probes of Nano-Catalysts and Correlative Structure–Reactivity Studies

Alayoǧlu

Somorjai

2014

Catal Lett

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“…Chiral map of SWCNTs without 7 large diameter ones, namely, (24,6), (17,15), (14,13), (28,6), (16,12), . There is no high selectivity to certain (n, m) species, but (8,4), (7,6), (8,6), (9, 7), (9,8) and (10,6) tubes occupy more than 37% of the total.…”

Section: Characterizations Of Swcnts Grown By Cvdmentioning

confidence: 99%

“…[8,10] In order to address the detailed structural change and track the evolution of catalyst nanoparticles, it is necessary to map the atomic structure in reactive environments using in situ environmental transmission electron microscopy (TEM). [11] In the work reported here, we present an acorn-like Pt-Fe2O3 catalyst for the growth of carbon nanotubes.…”

Section: Introductionmentioning

confidence: 99%

Environmental transmission electron microscopy investigations of Pt-Fe2O3 nanoparticles for nucleating carbon nanotubes

Zhang

Jiang

et al. 2016

Carbon

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“…[34] Some particular techniques of importance to the examples that follow are optical sum frequency generation spectroscopy, allowing the observation of molecular adsorbates, and synchrotron X-ray absorption and photoelectron spectroscopies, permitting atomic-level, element specific structural characterisation of the catalyst. We have also recently used in situ TEM to observe changes to PtCo nanoparticles under H 2 atmospheres [35,36] and in situ diffraction to observe the oxidation / reduction of mesoporous ceria supports (indicated by a substantial change in lattice parameter) under reducing and oxidising conditions. [37] Sum frequency generation (SFG) spectroscopy, developed by Shen and coworkers in the late 1980s, [38] is a technique which lends itself very well to studies of catalyst surfaces, due to its inherent interfacial sensitivity -even for buried interfaces.…”

Section: In Situ Techniques For Studying Nanoparticle Catalystsmentioning

confidence: 99%

Conquering Catalyst Complexity: Nanoparticle Synthesis and Instrument Development for Molecular and Atomistic Characterisation Under In Situ Conditions

Somorjai

Beaumont

2015

Top Catal

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. (2015) 'Conquering catalyst complexity : nanoparticle synthesis and instrument development for molecular and atomistic characterisation under in situ conditions.', Topics in catalysis., 58 (10). pp. 560-572. Further information on publisher's website:http://dx.doi.org/10.1007/s11244-015- Publisher's copyright statement:The nal publication is available at Springer via http://dx.doi.org/10.1007/s11244-015-0398-5Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. resolution in situ techniques with atomically and molecularly well-defined nanoparticle catalysts to achieve this goal. In particular we focus on mono-dispersed metal nanoparticles in the 0.8 -10 nm range with precise size distribution provided by modern colloidal synthetic techniques. These have been used in conjunction with a range of in situ techniques for understanding the complexity of a number of catalytic phenomena. Drawing on the nanoparticle size discrimination afforded by this approach, most metal nanoparticle catalysed covalent bond making/breaking reactions are identified as being structure sensitive, even when that was previously not thought to be the case. Small nanoparticles, below 2 nm, have been found to have changes of electronic structure that give rise to high oxidation state clusters under reaction conditions. These have been utilized to heterogenize typically homogeneous catalytic reactions using metal nanoclusters in the range of 40 atoms or less to carry out reactions on their heterogenized surfaces that would typically be expected only to occur at the higher oxidation state metal centre of a homogeneous organometallic catalyst. The combination of in-situ techniques and highly controlled metal nanoparticle structure also allows valuable insights to be achieved in understanding the mechanisms of multicomponent catalysts, catalysis occurring in different fluid phases and phenomena occurring at the metal-oxide interface.

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Revealing the Atomic Restructuring of Pt–Co Nanoparticles

Cited by 169 publications

References 32 publications

Nanocatalysis II: In Situ Surface Probes of Nano-Catalysts and Correlative Structure–Reactivity Studies

Nanocatalysis II: In Situ Surface Probes of Nano-Catalysts and Correlative Structure–Reactivity Studies

Environmental transmission electron microscopy investigations of Pt-Fe2O3 nanoparticles for nucleating carbon nanotubes

Conquering Catalyst Complexity: Nanoparticle Synthesis and Instrument Development for Molecular and Atomistic Characterisation Under In Situ Conditions

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