The delicate balance of phase speciation in bimetallic nickel cobalt nanoparticles

Palazzolo, Alberto; Poucin, Cyprien; Freitas, Alexy P.; Ropp, Anthony; Bouillet, Corinne; Ersen, Ovidiu; Carenco, Sophie

doi:10.1039/d2nr00917j

Cited by 9 publications

(13 citation statements)

References 58 publications

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“…However, it can be noted that these diameters might be slightly higher than these of the Ni NPs (10.5 � 1.2 nm), consistently with the formation of a cobalt shell, which is in agreement with our previous work on thicker shells. [29] The shell thickness is moreover consistent with these expected from our geometrical model. In agreement with the presence of a thin cobalt shell, no crystalline cobalt phase was detected by X-ray diffraction on powder (showed on Figure S3).…”

Section: Chemcatchemsupporting

confidence: 86%

“…The present work aims at providing a deeper understanding of the nature of this catalytic active site for phenylsilane activation, based on an experimental approach. For NiCo nanoparticles, we recently developed a synthetic route that allows the controlled deposition of cobalt on a fcc Ni core [29] . We propose here to investigate the catalytic activity of NiCo nanoparticles with a controlled sub‐stoichiometric amount of Co surface sites to better understand the influence of their close environment (Co‐rich or Ni‐rich).…”

Section: Introductionmentioning

confidence: 99%

“…For NiCo nanoparticles, we recently developed a synthetic route that allows the controlled deposition of cobalt on a fcc Ni core. [29] We propose here to investigate the catalytic activity of NiCo nanoparticles with a controlled sub-stoichiometric amount of Co surface sites to better understand the influence of their close environment (Co-rich or Ni-rich). We showed that the trend in phenylsilane conversion is consistent with cobalt being more active when surrounded by a Co-rich environment.…”

Section: Introductionmentioning

confidence: 99%

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Influence of the Cobalt Active Site Neighbours in NiCo Nanocatalysts for Phosphine‐Assisted Silane Activation

Ropp

Carenco

2023

ChemCatChem

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NiCo nanoparticles are active catalysts for a number of reactions, as an interesting alternative to noble metals. In particular, phosphine‐covered NiCo nanoparticles with a 1 : 1 metal ratio were found to be active at room temperature for Si−H bond activation. However, it was unclear which of the two metals was the active site and if the neighbouring atoms influenced the reaction efficiency. We designed nanoparticles with a nickel core and a limited amount of cobalt surface sites, just below or just above a monolayer amount, to investigate this question. We showed that the trend in catalytic activity is consistent with cobalt being the active site, and it shows a higher activity when its immediate neighbours are cobalt atoms. This was consistently observed with two phosphine ligands, PPh3 and PnBu3, while the first allowed a higher conversion rate than the second.

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Section: Chemcatchemsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of the Cobalt Active Site Neighbours in NiCo Nanocatalysts for Phosphine‐Assisted Silane Activation

Ropp

Carenco

2023

ChemCatChem

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“…Particles synthesized via this method have hollow morphology with diameters of approximately 8.6 ± 2.1 nm. We presume this is a reflection of the Kirkendall effect (faster diffusion of Ni and Co outward, than P inward), but the core–shell morphology associated with NiCo bimetallic alloys may also be a contributing factor. − Utilizing Scheme , Path C, with these precursors, a Ni 2– x Co x P solid solution was isolated with the PXRD patterns matching with the reference pattern for Ni 2 P (Figure c). TEM and EDS revealed particles with spherical morphology (diameter ∼8.8 ± 1.3 nm) and chemical composition of Ni 1.1 Co 0.9 P 1.1 , respectively.…”

Section: Resultsmentioning

confidence: 99%

Homogeneous Nanoparticles of Multimetallic Phosphides via Precursor Tuning: Ternary and Quaternary M₂P Phases (M = Fe, Co, Ni)

2022

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Transition metal phosphides (TMPs) are a highly investigated class of nanomaterials due to their unique magnetic and catalytic properties. Although robust and reproducible synthetic routes to narrow polydispersity monometallic phosphide nanoparticles (M2P; M = Fe, Co, Ni) have been established, the preparation of multimetallic nanoparticle phases (M2–x M′ x P; M, M′ = Fe, Co, Ni) remains a significant challenge. Colloidal syntheses employ zero-valent metal carbonyl or multivalent acetylacetonate salt precursors in combination with trioctylphosphine as the source of phosphorus, oleylamine as the reducing agent, and additional solvents such as octadecene or octyl ether as “noncoordinating” cosolvents. Understanding how these different metal precursors behave in identical reaction environments is critical to assessing the role the relative reactivity of the metal precursor plays in synthesizing complex, homogeneous multimetallic TMP phases. In this study, phosphorus incorporation as a function of temperature and time was evaluated to probe how the relative rate of phosphidation of organometallic carbonyl and acetylacetonate salt precursors influences the homogeneous formation of bimetallic phosphide phases (M2–x M′ x P; M, M′ = Fe, Co, Ni). From the relative rate of phosphidation studies, we found that where reactivity with TOP for the various metal precursors differs significantly, prealloying steps are necessary to isolate the desired bimetallic phosphide phase. These insights were then translated to establish streamlined synthetic protocols for the formation of new trimetallic Fe2–x–y Ni x Co y P phases.

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“…This is yet another example of how delicate the production of phase‐ and morphology‐controlled nanoparticles can be [33] . Potential consequences are slight variations of the specific surface and the precise nature of surface sites.…”

Section: Resultsmentioning

confidence: 99%

Phosphine‐Enhanced Semi‐Hydrogenation of Phenylacetylene by Cobalt Phosphide Nano‐Urchins

Ropp,

André,

Carenco

2023

ChemPlusChem

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Transition metal phosphides are promising, selective, and air‐stable nanocatalysts for hydrogenation reactions. However, they often require fairly high temperatures and H2 pressures to provide quantitative conversions. This work reports the positive effect of phosphine additives on the activity of cobalt phosphide nano‐urchins for the semi‐hydrogenation of phenylacetylene. While the nanocatalyst's activity was low under mild conditions (7 bar of H2, 100 °C), the addition of a catalytic amount of phosphine remarkably increased the conversion, e. g., from 13 % to 98 % in the case of PnBu3. The heterogeneous nature of the catalyst was confirmed by negative supernatant activity tests. The catalyst integrity was carefully verified by post‐mortem analyses (TEM, XPS, and liquid 31P NMR). A stereo‐electronic map was proposed to rationalize the activity enhancement provided over a selection of nine phosphines: the strongest effect was observed for low to moderately hindered phosphines, associated with strong electron donor abilities. A threshold in phosphine stoichiometry was revealed for the enhancement of activity to occur, which was related to the ratio of phosphine to surface cobalt atoms.

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The delicate balance of phase speciation in bimetallic nickel cobalt nanoparticles

Abstract: Bimetallic nickel-cobalt nanoparticles are highly sought for their potential as catalytic and magnetic nanoparticles. These are typically prepared in organic solvents in the presence of strong stabilizing ligands such as...

Cited by 9 publications

References 58 publications

Influence of the Cobalt Active Site Neighbours in NiCo Nanocatalysts for Phosphine‐Assisted Silane Activation

Influence of the Cobalt Active Site Neighbours in NiCo Nanocatalysts for Phosphine‐Assisted Silane Activation

Homogeneous Nanoparticles of Multimetallic Phosphides via Precursor Tuning: Ternary and Quaternary M₂P Phases (M = Fe, Co, Ni)

Phosphine‐Enhanced Semi‐Hydrogenation of Phenylacetylene by Cobalt Phosphide Nano‐Urchins

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The delicate balance of phase speciation in bimetallic nickel cobalt nanoparticles

Abstract: Bimetallic nickel-cobalt nanoparticles are highly sought for their potential as catalytic and magnetic nanoparticles. These are typically prepared in organic solvents in the presence of strong stabilizing ligands such as...

Cited by 9 publications

References 58 publications

Influence of the Cobalt Active Site Neighbours in NiCo Nanocatalysts for Phosphine‐Assisted Silane Activation

Influence of the Cobalt Active Site Neighbours in NiCo Nanocatalysts for Phosphine‐Assisted Silane Activation

Homogeneous Nanoparticles of Multimetallic Phosphides via Precursor Tuning: Ternary and Quaternary M2P Phases (M = Fe, Co, Ni)

Phosphine‐Enhanced Semi‐Hydrogenation of Phenylacetylene by Cobalt Phosphide Nano‐Urchins

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Homogeneous Nanoparticles of Multimetallic Phosphides via Precursor Tuning: Ternary and Quaternary M₂P Phases (M = Fe, Co, Ni)