Hydrogen-induced Ostwald ripening of cobalt nanoparticles on carbon nanotubes

Vece, Marcel Di; Zoican-Loebick, Codruta; Pfefferle, Lisa D.

doi:10.1007/s11051-013-2234-9

Cited by 3 publications

(4 citation statements)

References 41 publications

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“…Although a few small clusters and particles have disappeared, the majority remain in the same location and of approximately the same size, suggesting at this temperature small mixed platinum–cobalt clusters may be stabilised by the carbon black support. Previous research with cobalt nanoparticles revealed Ostwald ripening to occur (Alloyeau et al ., ; Di Vece et al ., ) but less so for platinum. Our previous in situ work showed that small platinum clusters became more faceted over time at 300–500 °C in hydrogen when supported on amorphous carbon with the number of isolated atoms reducing in quantity over time (Boyes et al ., ; Gai et al ., ).…”

Section: Resultsmentioning

confidence: 94%

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Direct observations of dynamic PtCo interactions in fuel cell catalyst precursors at the atomic level using E(S)TEM

Ward

Theobald

Sharman

et al. 2017

Journal of Microscopy

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Reduction reactions in practical bimetallic platinum-cobalt electrode catalyst precursors containing platinum, cobalt and cobalt oxides in hydrogen at 200, 450 and 700 °C for 6 h have been studied in situ using an aberration corrected environmental (scanning) transmission electron microscope (AC E(S)TEM). Little difference was observed in reduction at 200 °C but during and after reduction at 450 °C, small nanoparticles less than 3 nm in diameter with tetragonal PtCo structures were observed and limited Pt Co ordering could be seen on the surfaces of larger nanoparticles. During and after reduction at 700 °C, fully ordered Pt Co and PtCo nanoparticles larger than 4 nm were produced and the average nanoparticle size almost trebled relative to the fresh precursor. After reduction at 450 and 700 °C, most nanoparticles were disordered platinum/cobalt alloys with fcc structure. After reduction at 700 °C many of the smallest nanoparticles disappeared suggesting Ostwald ripening had occurred. Mechanisms concerning the thermal transformation of mixed cobalt and platinum species are discussed, offering new insights into the creation of bimetallic platinum-cobalt nanoparticles in fuel cell catalysts.

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Section: Resultsmentioning

confidence: 94%

“…A few small isolated clusters have disappeared suggesting that they may have undergone Ostwald ripening. Previous (S)TEM work suggests that cobalt Ostwald ripening can occur at 450 °C in hydrogen (Di Vece et al ., ).…”

Section: Resultsmentioning

confidence: 97%

Direct observations of dynamic PtCo interactions in fuel cell catalyst precursors at the atomic level using E(S)TEM

Ward

Theobald

Sharman

et al. 2017

Journal of Microscopy

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“…of the cobalt nanoparticles at the surface of the CNTs, which was otherwise observed when working at elevated temperatures (400 °C) [21]. Upon hydrogenation only cobalt atoms and cyclooctane, a non-coordinating molecule, are formed in the reaction medium.…”

Section: Introductionmentioning

confidence: 98%

“…Based on this expertise, we investigated the preparation of cobalt-CNT composites (CNT@Co) by direct decomposition of an organometallic cobalt complex, [Co(η 4 -C 8 H 12 ) (η 3 -C 8 H 13 )], in the presence of suspended CNTs. Hydrogenation of this complex can be performed at room temperature which can favor attachment of cobalt onto the CNT and limit Ostwald ripening of the cobalt nanoparticles at the surface of the CNTs, which was otherwise observed when working at elevated temperatures (400 °C) [21]. Upon hydrogenation only cobalt atoms and cyclooctane, a non-coordinating molecule, are formed in the reaction medium.…”

Section: Introductionmentioning

confidence: 99%

Co nanocrystals engineering

Fontaíña-Troitiño

Ciuculescu-Pradines

Correa‐Duarte

et al. 2017

Adv. Nat. Sci: Nanosci. Nanotechnol.

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Organometallic chemistry plays an increasing role in the synthesis of nanoparticles, as it provides a reliable access to metal nanoparticles with efficient control over their morphology, organization and surface chemistry. In case of magnetic nanoparticles, the synthetic tools provided by organometallic chemistry allow access to nanomaterials of high magnetization, meaning that no dead surface magnetic layer is observed. These objects are thus good candidates to be used as building blocks in composite materials of high added value. This paper reports on the organometallic synthesis of composites made of cobalt nanoparticles and carbon nanotubes. TEM investigations show that attachment of cobalt spheres and rods along the carbon nanotubes is achieved, the rods and tube long axis being aligned parallel to one another.

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