Supported Catalysts from Chemical Vapor Deposition and Related Techniques

Tada, Mizuki; Iwasawa, Yasuhiro

doi:10.1002/9783527610044.hetcat0026

Cited by 7 publications

(5 citation statements)

References 121 publications

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“…CVD (chemical vapor deposition) is a common alternative to solution methods that eliminates some of the deficiencies in structural control discussed above. , In CVD, a gaseous precursor stream is chemisorbed onto the support. The absence of solvent facilitates precursor diffusion inside pores and precludes drying steps during which active phase redistribution may occur.…”

Section: Traditional Supported Oxide Catalyst Synthesismentioning

confidence: 99%

Design Strategies for the Molecular Level Synthesis of Supported Catalysts

2011

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Supported catalysts, metal or oxide catalytic centers constructed on an underlying solid phase, are making an increasingly important contribution to heterogeneous catalysis. For example, in industry, supported catalysts are employed in selective oxidation, selective reduction, and polymerization reactions. Supported structures increase the thermal stability, dispersion, and surface area of the catalyst relative to the neat catalytic material. However, structural and mechanistic characterization of these catalysts presents a formidable challenge because traditional preparations typically afford complex mixtures of structures whose individual components cannot be isolated. As a result, the characterization of supported catalysts requires a combination of advanced spectroscopies for their characterization, unlike homogeneous catalysts, which have relatively uniform structures and can often be characterized using standard methods. Moreover, these advanced spectroscopic techniques only provide ensemble averages and therefore do not isolate the catalytic function of individual components within the mixture. New synthetic approaches are required to more controllably tailor supported catalyst structures. In this Account, we review advances in supported catalyst synthesis and characterization developed in our laboratories at Northwestern University. We first present an overview of traditional synthetic methods with a focus on supported vanadium oxide catalysts. We next describe approaches for the design and synthesis of supported polymerization and hydrogenation catalysts, using anchoring techniques which provide molecular catalyst structures with exceptional activity and high percentages of catalytically significant sites. We then highlight similar approaches for preparing supported metal oxide catalysts using atomic layer deposition and organometallic grafting. Throughout this Account, we describe the use of incisive spectroscopic techniques, including high-resolution solid state NMR, UV-visible diffuse reflectance (DRS), UV-Raman, and X-ray absorption spectroscopies to characterize supported catalysts. We demonstrate that it is possible to tailor and isolate defined surface species using a molecularly oriented approach. We anticipate that advances in catalyst design and synthesis will lead to a better understanding of catalyst structure and function and, thus, to advances in existing catalytic processes and the development of new technologies.

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Section: Traditional Supported Oxide Catalyst Synthesismentioning

confidence: 99%

Design Strategies for the Molecular Level Synthesis of Supported Catalysts

2011

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“…31,131 In this chapter, the structures and catalytic performance of metal-cluster catalysts prepared by CVD (chemical vapor deposition), which can produce uniform metal structures on oxide surfaces. 132 In situ characterization of the metal-cluster catalysts prepared by CVD revealed essences of catalysis and relationships between catalyst structure and reactivity. 133136 …”

Section: Creation Of Novel Metal Clusters By Chemical Vapor Depositiomentioning

confidence: 99%

Surface-Mediated Design and Catalytic Properties of Active Metal Complexes for Advanced Catalysis Creation

Tada¹

2010

Bulletin of the Chemical Society of Japan

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Molecular-scale design of catalytically active structures at oxide surfaces is highlighted, focusing on our recent challenges for selective heterogeneous catalysis. We found novel structural transformations of supported metal complexes on oxide surfaces and achieved unique selective catalysis for various chemical syntheses. In this account, the advanced design of supported metal-complex catalysts on oxide surfaces and the in situ characterization of their structural kinetics, which means kinetics of structural changes of catalysts themselves, under catalyst-working conditions are reviewed. Surface-Mediated Design of Catalytically ActiveStructures for Selective Catalysis 1.1 Introduction: Metal-Complex Attaching on Oxide Surfaces. Heterogeneous solid catalysts have been widely utilized for the industrial production of many synthetic chemicals. The advantages of heterogeneous catalysts are not only the separation of catalysts and products from reaction media but also their high durability and catalytic activities resulting from the unique structures of catalytically active sites at solid surfaces. Relationships among the metal structures, organized environment, and the catalytic properties of surface species tell us the nature of catalysis and new strategy for rational design of heterogeneous catalysts.Metal-complex attachment to oxide surfaces is a practical way to produce molecularly regulated structures of active metal species on oxide surfaces, and subsequent structural transformation in a controllable manner often provides unique regulated metal structures active for selective catalytic reactions. 116 There are several types of metal-complex attachment techniques: coordination of metal-complex precursors to immobilized ligands on organic polymers, 1721 coordination of metal-complex precursors to functional ligands bound to oxide surfaces, 2,4,2225 intercalation into clay materials, 26 ion exchange into porous materials such as zeolite and mesoporous silica, 27 and direct attachment of metal-complex precursor onto oxide surfaces. 3,6,11,28,29 The interfacial attachment between a metal complex and an oxide surface can produce unique metal coordination different from the original metal-complex precursor. For example, SiOH is reacted with a M(CH 3 ) complex and a M(OSi) complex is produced, releasing CH 4 . A chemical bond between a metal-complex precursor and a support surface modifies the reactivity of the supported metal complex, resulting in novel catalytic activity the precursor complex does not exhibit. 3,6,11,28,29 Traditional ion-exchange on zeolites and intercalation to clay materials are also typical ways to introduce metal species onto solid supports although the valences and types of metal precursors are restricted. 4 Direct reactions of metal-complex precursors and hydroxy groups on oxide surfaces create novel metal-coordination structures, and many important factors for selective catalysis can be controlled at the interface, such as electronic properties and coordination sphere of the attached metal...

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“…In contrast to the wet-chemical impregnation process, the incorporation of iron and carbon was obtained within a single step. The embedded iron can be utilized to catalyze the graphitization of the decomposed carbon, , significantly altering the textural properties of the obtained carbon replica . Additionally, the CVD of ferrocene employing SiO 2 @mSiO 2 templates was reported for the synthesis of hollow graphitic carbon spheres. − …”

Section: Introductionmentioning

confidence: 99%

Chemical Vapor Deposition of Hollow Graphitic Spheres for Improved Electrochemical Durability

Knossalla

Mielby

Göhl

et al. 2021

ACS Appl. Energy Mater.

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The wet-chemical synthesis of hollow graphitic spheres, a highly defined model catalyst support for electrocatalytic processes, is laborious and not scalable, which hampers potential applications. Here, we present insights into the chemical vapor deposition (CVD) of ferrocene as a simple, scalable method to synthesize hollow graphitic spheres (HGS cvd ). During the CVD process, iron and carbon are embedded in the pores of a mesoporous silica template. In a subsequent annealing step, iron facilitates the synthesis of highly ordered graphite structures. We found that the applied temperature treatment allows for controlling of the degree of graphitization and the textural properties of HGS cvd . Further, we demonstrate that platinum loaded on HGS cvd is significantly more stable during electrochemical degradation protocols than catalysts based on commercial high surface area carbons. The established CVD process allows the scalable synthesis of highly defined HGS and therefore removes one obstacle for a broader application.

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Supported Catalysts from Chemical Vapor Deposition and Related Techniques

Abstract: The sections in this article are Chemical Vapor Deposition ( CVD ) Technique CVD Precursors and Equipment CVD Catalysts Gold ( Au ) Coba… Show more

Cited by 7 publications

References 121 publications

Design Strategies for the Molecular Level Synthesis of Supported Catalysts

Design Strategies for the Molecular Level Synthesis of Supported Catalysts

Surface-Mediated Design and Catalytic Properties of Active Metal Complexes for Advanced Catalysis Creation

Chemical Vapor Deposition of Hollow Graphitic Spheres for Improved Electrochemical Durability

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