Synthesis of Dispersible Pd@CeO<sub>2</sub>Core−Shell Nanostructures by Self-Assembly

Cargnello, Matteo; Wieder, Noah L.; Montini, Tiziano; Gorte, Raymond J.; Fornasiero, Paolo

doi:10.1021/ja909131k

Cited by 222 publications

(192 citation statements)

References 55 publications

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“…Xu and coworkers compared the visible-light photoactivity with that of traditional Pd/CeO 2 and commercial CeO 2 . 87 The peaks in the photoluminescent spectra of the Pd@CeO 2 core-shell nanostructure are much lower than those in the other two samples, indicating the efficiently prolonged lifetime of electron-hole pairs, which is in line with the photocurrent-voltage plots displayed in Figure 19b. Compared with traditional Pd/CeO 2 and commercial CeO 2 , the photocurrent density of Pd@CeO 2 is significantly greater, which may be the main reason for the longer life span achieved for the Pd@CeO 2 core-shell sample.…”

Section: Anti-sintering Capabilitiessupporting

confidence: 76%

“…87 Complete conversion of CH 4 was observed at 400°C ( Figure 18a). All other reference samples achieved the complete CH 4 conversion above 700°C.…”

Section: Anti-sintering Capabilitiesmentioning

confidence: 98%

“…For example, three-way catalysts should work above 400°C, and in the methane combustion reaction, the high stability of methane hinders the catalytic reaction; hence, the complete conversion temperature is always higher than 600°C. 87 With such high working temperatures, the noble metals tend to deactivate through the loss of active surface. The CeO 2 -encapsulated noble metal nanocrystal approach offers a powerful tool for minimizing deactivation of the catalyst during the sintering processes.…”

Section: Anti-sintering Capabilitiesmentioning

confidence: 99%

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CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

2015

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Encapsulation of small noble metal nanoparticles has received attention owing to the resulting highly increased stability and high catalytic activity and selectivity. Among the types of inert metal oxides, CeO 2 is unique. It is inexpensive and highly stable, and, more importantly, the unique electronic configuration gives it a strong capability to provide active oxygen. The method of fabricating CeO 2 -encapsulated noble metal nanocatalysts is determined by the requirements of the application. In this review, we first describe the various types of encapsulated noble metals and then the current developments of synthesis in detail, including the types of hybrid nanostructures and successful synthetic strategies. The following section, concerning catalytic applications, is divided into three topics: anti-sintering capabilities, catalytic activities and selectivities. We hope that this review of the recent achievements and the proposed strategy for addressing the emerging challenges will inspire further developments in this research area. NPG Asia Materials (2015) 7, e179; doi:10.1038/am.2015.27; published online 8 May 2015 INTRODUCTIONNoble metal catalysts have received much attention in the past decade because of their unique chemical and physical properties, and they have been widely applied in industrial use. [1][2][3][4][5][6][7][8][9][10] With the help of noble metal catalysts, environmental friendly catalysis resulting in the decreased production of pollutants, waste minimization and new synthetic routes that circumvent modern synthetic techniques such as Sonogashira-, Heck-and Miyaura-Suzuki-type reactions can be easily realized. 11-15 However, for most technologically important chemical processes, noble metal catalysts spontaneously aggregate and grow to reduce the surface energy, which limits the catalysts' lifetime and efficiency. The ultra-high prices of noble metals have also seriously limited their further development. Because of the development of modern industry, there remains a critical need for robust, simple and readily controllable routes to fabricate highly active, stable and recyclable nanocatalysts.To maximize the catalytic performance of noble metals and reduce the quantity used, it is necessary to load the active centers on a substrate. [16][17][18][19][20] A suitable substrate not only provides a high surface area to stabilize small nanoparticles (NPs) under long-term catalysis but also renders hybrid junctions with rich redox reactions on the two-phase interface. With the development of synthetic techniques in nanoscience, small noble metal NPs, especially atomically precise nanoclusters/metal oxide hybrid nanostructures, have been successfully fabricated very recently, and these materials exhibit remarkable enhanced catalytic activity and selectivity. [21][22][23] However, this simple loading form cannot meet the growing demand for the stability, because the noble metal catalysts contain numerous exposed surfaces

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Section: Anti-sintering Capabilitiessupporting

confidence: 76%

“…87 Complete conversion of CH 4 was observed at 400°C ( Figure 18a). All other reference samples achieved the complete CH 4 conversion above 700°C.…”

Section: Anti-sintering Capabilitiesmentioning

confidence: 98%

Section: Anti-sintering Capabilitiesmentioning

confidence: 99%

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CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

2015

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“…[5] The supramolecular Pd@CeO 2 core-shell structures were prepared according to published procedures. [44] Briefly, the method is based on the self-assembly between Ce IV tetradecyl alkoxide and functionalized Pd nanoparticles protected by 11-mercaptoundecanoic acid (MUA). A controlled hydrolysis in the presence of dodecanoic acid leads to the formation of the Pd@CeO 2 structures, in which the CeO 2 shell is composed of small crystallites ( % 3 nm) organized around the preformed metal particles.…”

Section: Catalyst Synthesismentioning

confidence: 99%

Methane Catalytic Combustion over Hierarchical Pd@CeO₂/Si‐Al₂O₃: Effect of the Presence of Water

et al. 2014

Self Cite

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The influence of water vapor on methane catalytic combustion was studied over a Pd@CeO2/Si‐Al2O3 catalyst, carefully designed to maximize Pd‐CeO2 interaction and prevent metal sintering and compared to a conventional impregnated catalyst with identical chemical composition. Although the nanostructured Pd@CeO2/Si‐Al2O3 catalyst is thermally stable, the addition of water to the reaction feed leads to a transient deactivation at low temperatures, consistent with the well documented competitive adsorption. In addition to this, the hierarchically structured catalyst exhibits an additional severe deactivation after methane oxidation in the presence of water vapor at 600 °C that can be reversed only by heating the catalyst above 700 °C. The presence of water in the reaction feed deactivates the conventional impregnated catalyst less severely and the activity largely returns upon water removal. Catalytic FTIR and CO‐chemisorption data indicate that this severe deactivation process in the hierarchical catalyst is due to the formation of stable OH groups on the surface of the ceria nanoparticles. These hydroxyl groups are suggested to significantly inhibit the oxygen spillover from the CeO2 nanoparticles to Pd, preventing its efficient re‐oxidation, as observed by operando X‐ray absorption near edge spectroscopy (XANES) experiments. At the same time, their presence can contribute to limit the gas phase accessibility of Pd, as indicated by the decrease of CO chemisorption capability. The presence of hydroxyls plays a minor role on the deactivation of the conventional catalyst at 600 °C.

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“…It is worth mentioning that the peculiar strong metal-support interaction of these materials may result in electronic deactivation. For instance, although ceria coated noble metals (Au@CeO 2 and Pd@CeO 2 ) are active [17,18], Pd@CeO 2 suffers from fast deactivation under reducing condition [19].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Catalytic Properties of Carbon-Nanotube-Supported RuO2 Catalyst Encapsulated in Silica Coating

Zhang

et al. 2011

Catal Lett

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A carbon-nanotube-supported RuO 2 nanocatalyst encapsulated in thin silica layer was successfully synthesized. The prior formation of silica over RuO 2 nanoparticles effectively hindered catalyst aggregation at high temperatures. The significant improvement of the resistance to sintering and the catalytic selectivity were demonstrated in competitive oxidation of n-butanol and i-butanol and methanol oxidative dehydrogenation.

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Synthesis of Dispersible Pd@CeO₂Core−Shell Nanostructures by Self-Assembly

Cited by 222 publications

References 55 publications

CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

Methane Catalytic Combustion over Hierarchical Pd@CeO₂/Si‐Al₂O₃: Effect of the Presence of Water

Synthesis and Catalytic Properties of Carbon-Nanotube-Supported RuO2 Catalyst Encapsulated in Silica Coating

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Synthesis of Dispersible Pd@CeO2Core−Shell Nanostructures by Self-Assembly

Cited by 222 publications

References 55 publications

CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

Methane Catalytic Combustion over Hierarchical Pd@CeO2/Si‐Al2O3: Effect of the Presence of Water

Synthesis and Catalytic Properties of Carbon-Nanotube-Supported RuO2 Catalyst Encapsulated in Silica Coating

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Synthesis of Dispersible Pd@CeO₂Core−Shell Nanostructures by Self-Assembly

Methane Catalytic Combustion over Hierarchical Pd@CeO₂/Si‐Al₂O₃: Effect of the Presence of Water