sophiecarenco

Small molecules such as CO₂ have been activated on metal nanoparticles for ages, eg. in the Sabatier process using nickel nanoparticles. However, the harsh conditions required with noble-metal free catalysts preclude the catalytic process from formingfunctional molecules. Rather, simple molecules such as methane are obtained, which stands as a strong limitation. In the NanoFLP projet, we aim at boosting the reactivity of these nanoparticles using adequate surface ligands in order to operate the catalytic reactions at room temperature and ambient pressure.

We selected a commercial aminophosphine, HETAP, as the phosphorus precursor to develop a robust synthesis crystalline Co₂P and Ni₂P nanoparticles with high yields on a 9 mmol scale. Moreover, modification of the nanoparticles via the addition of a molecular Lewis base triggered catalytic activity of the colloidal suspension at low temperature for the hydrogenation of phenylacetylene. We delineated the most efficient phosphines in the case of a Ni₂P catalyst, using a stereoelectronic map of 13 phosphines.

A. Ropp , S. Carenco, Inorg. Chem. 2024, DOI 10.1021/acs.inorgchem.4c02743

We designed a low-temperature synthetic route for CeO₂ nanorods. We employed near-ambient-pressure X-ray photoelectron spectroscopy to monitor the cerium surface oxidation state during the initial annealing of the nanopowder, followed by exposure to a moderate pressure of H₂. We demonstrate that H₂ homolytic splitting at cerium sites is the main activation process at 100 °C, leading to the oxidation of 30% of the surface cerium atoms, while the H₂ splitting at oxygen sites was absent.

R. F. André, J.-J. Gallet, F. Bournel, S. Carenco, ChemCatChem 2024, DOI 10.1002/cctc.202400163.

We show that phosphines with adequate steric hindrance (e.g., PnBu₃ and PiBu₃) lower the onset temperature for phenylacetylene hydrogenation by nickel NPs under 7 bar of H₂, by ca 10 to 20 °C depending on the NP diameter. This result is of conceptual value because the hydrogenation may have been driven by the frustrated Lewis pair (FLP) between the Lewis basic phosphine and the Lewis acid nickel surface, forming a so-called “NanoFLP”. Moreover, we demonstrated that less than 2 phosphines per Ni surface atom are enough for the effect to arise. We showed that other terminal alkynes, like 1-octyne, can be hydrogenated with this method.

K. Azouzi, A. Ropp, S. Carenco, ACS Catalysis 2024, DOI 10.1021/acscatal.4c00054.

We report 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. A stereo-electronic map was proposed: the strongest effect was observed for low to moderately hindered phosphines, associated with strong electron donor abilities.

A. Ropp, R. F. André, S. Carenco, ChemPlusChem 2023, DOI 10.1002/cplu.202300469.

NiCo nanoparticles are active catalysts at room temperature for Si−H bond activation. We designed nanoparticles with a nickel core and a limited amount of cobalt surface sites to clarify which of the two metals was the active site and if the neighbouring atoms influenced the reaction efficiency. 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.

A. Ropp, S. Carenco, ChemCatChem 2023, DOI 10.1002/cctc.202300400.

While the literature contains tens of protocols to prepare cerium oxide nanoparticles from Ce(III) precursors, there is still an open question regarding the time at which the cerium oxidation occurs and the role of hydroxide phases in this process. This article identifies an oxyhydroxide phase of Ce(IV) of the chemical formula CeO(OH)₂ as a key intermediate and proposes a crystal structure for it.

R. F. André, G. Rousse, C. Sassoye, M. Avdeev, B. Lassalle-Kaiser, B. Baptiste and S. Carenco, Chem. Mater. 2023, DOI 10.1021/acs.chemmater.3c00486.

Here, we studied the organocatalyzed hydrosilylation of benzaldehyde with a phosphine, introduced at 10 mol %, and phenylsilane at room temperature. The best results of the screening over 13 phosphines and phosphites were obtained with linear trialkylphoshines (PMe₃, PnBu₃, POct₃), indicating the importance of their nucleophilicity. The products of the hydrosilylation were identified, allowing a monitoring of the concentration in the different species.

R. F. André, A. Palazzolo, C. Poucin, F. Ribot, S. Carenco, ChemPlusChem 2023, doi 10.1002/cplu.202300038

We propose the concept of a NanoFLP in a colloidal solution where one partner is a phosphine Lewis base and the other is the Lewis acid surface of a NiCo nanoparticle. We attempt to apply this concept to the hydrosilylative reduction of benzaldehyde. We identify a correlation between the Tolman cone angle and the silane conversion, consistent with both mechanisms; however, we found no clear correlation between the Tolman electronic parameter and the reaction outcome. Structural analyses evidenced that the nanoparticles are not altered during the reaction, which led us to propose the formation of a NanoFLP as a transient species in solution.

A. Palazzolo, S. Carenco. Chem. Mater. 2021, acs.chemmater.1c03105.

We investigated here crystalline nickel carbide nanoparticles as catalysts in colloidal suspension for hydrogenation reactions under H₂ (7 bar) and below 100°C. Polar solvents appeared comparatively more favorable than less polar ones for the hydrogenation of two model substrates: nitrobenzene and phenylacetylene. Furthermore, the presence of water in the solvent mix was mostly favorable to the hydrogenation yield. We expanded the scope to a variety of aldehydes, ketones, esters, nitriles and unsaturated hydrocarbons.

R. F. André, L. Meyniel, S. Carenco, Cat. Sci. Tech. 2022, doi 10.1039/D2CY00894G

Due to the variety of cobalt crystallographic phases, forming fcc nanoparticles rather than phase mixture is a challenging endeavor. We found optimized conditions to form size-controlled fcc NiCo nanoparticles from preformed Ni nanoparticles. We then investigated the early stages of Co nucleation on the nickel using a lower stoichiometry of Co, down to 0.05 equiv. vs. Ni. We showed that cobalt reacts first on the nickel nanoparticles but easily forms cobalt-rich larger aggregates in the further steps of the reaction.

A. Palazzolo, C. Poucin, A. P. Freitas, A. Ropp, C. Bouillet, O. Ersen, S. Carenco, Nanoscale 2022, doi 10.1039/D2NR00917J.

X-ray absorption near-edge structure (XANES) is a particularly well-adapted technique to study the L_2,3-edges of Mo (2520–2625 eV). It provides information on both the electronic and local structures of metal-containing species and allows drawing structure–activity relationships. However, L_2,3-edges are difficult to interpret, especially for 4d and 5d transition metals. In this work, we provide a method for their interpretation based on a library of spectra of simple Mo compounds. We suggest using the L₃-edge to determine the oxidation state and the L₂-edge to gain insight on the geometry around Mo atoms. This method is then applied to a series of molybdenum sulfide compounds to rationalize their structures.

A.P. Freitas, R. F. André, C. Poucin, T. K.-C. Le, J. Imbao, B. Lassalle-Kaiser, S. Carenco. Guidelines for the Molybdenum Oxidation State and Geometry from X-Ray Absorption Spectroscopy at the Mo L_2,3-Edges. J. Phys. Chem. C 2021, 10.1021/acs.jpcc.1c01875.

Transition metal carbides (TMCs) have attracted great interest due to their mechanical and catalytic properties but their syntheses generally require energy-consuming processes with temperatures above 800 °C. We report here a solid-state metathesis reaction between metal chlorides (ZrCl₄, NbCl₅, MoCl₃, MoCl₅, HfCl₄, TaCl₅, WCl₆) and potassium dispersed in carbon. Within seconds, it produces carbide or metallic nanoparticles of diameter below 50 nm supported on carbon. Based on thermodynamic and kinetic considerations, we propose a mechanism explaining the coexistence of several phases (metal, carbide, hydride) and their occurrence at each step of the reaction.

R. F. André, F. D'Accriscio, A. P. Freitas, G. Crochet, C. Bouillet, M. Bahri, O. Ersen, C. Sanchez, S. Carenco, Green Chem., 2021, 10.1039/D1GC01097B

Copper nanoparticle synthesis was studied by thorough characterization of the organic reactions happening during the synthesis. The reduction of copper(II) acetate by oleylamine resulted in a high amount of water and few by-products while the reduction of copper(II) acetylacetonate resulted in a low amount of water and many products. The nanoparticles showed different abilities to further dehydrogenate and transaminate oleylamine in the synthesis reaction pot. This was explained by the presence of a copper oxide phase in the nanoparticles prepared from copper acetate.

A. Pesesse, S. Carenco, Cat. Sci. Tech.., 2021, 10.1039/D1CY00639H.

Surface and core of inorganic nanoparticles may undergo profound transformations in their environment of use. Accurate description is key to understand and control surface reactivity.

Through a selection of case studies, this feature article proposes a journey from surface science to nanoparticle design, while illustrating state-of-the-art spectroscopies that help provide a relevant description of inorganic nanoparticles in the context of surface reactivity.

S. Carenco, Chem. Commun. 2018, 54, 6719-6727

CO₂ can be converted into hydrocarbon using cobalt-based catalysts. However and to our surprise, core-shell nickel-cobalt nanoparticles produced oxygenated molecules instead (CO, methanol, formaldehyde).

We showed that, as a result of the heating and the presence of reactive gas, nickel was able to migrate to the surface of the nanoparticle. Alongside, small amounts of phosphorus were also found to get exposed to the surface. This phosphorus actually comes from the ligands (TOP) that were required in the first step of the nanoparticles synthesis but partially decomposed upon heating.

The active catalyst should not be seen as a cobalt surface, but rather as a nickel-cobalt alloy containing significant level of phosphide species.

S. Carenco, C.-H. Wu, A. Shavorskiy, S. Alayoglu, G. A. Somorjai, H. Bluhm, M. Salmeron, Small 2015, 11, 3045

CO2 methanation is an old process but it is one of the keys to produce chemicals of interest. One of the research trend is to go to lower reaction temperatures, which promote highly selective reactions (i.e. formation of methane without carbon monoxyde by-products). Ruthenium nanoparticles are active at low temperature in this process.

Near-Ambient-Pressure X-Ray Photoelectron Spectroscopy (NAP-XPS) was used to monitoring ruthenium nanoparticles deposited on a tailored TiO2 surface. We showed that the ruthenium is metallic under model reaction conditions and we also were able to analyze the nature of the adsorbates as a function of the temperature.

S. Carenco, C. Sassoye, M. Faustini, P. Eloy, D. P. Debecker, H. Bluhm, M. Salmeron, J. Phys. Chem. C 2016, 120, 15354

Carbon monoxide is a ubiquitous molecule in surface science, materials chemistry, catalysis and nanotechnology. Its interaction with a number of metal surfaces is at the heart of major processes, such as Fischer-Tropsch synthesis or fuel-cell optimization. Recent works have highlighted the ability of metal surfaces and nanoparticles to undergo restructuring after exposure to CO under fairly mild conditions, generating nanostructures. This Minireview deals with such nanostructuring, and discusses the driving force in reversible and non-reversible situations.

S. Carenco, Chem. Eur. J . 2014, 20, 10616

Just published in the French journal "L'Actualité chimique": a feature article about our ERC Research program on NanoFLP, or "nanoparticles as partners in Frustrated Lewis Pairs".

It describes our recent works on this topic, with a focus on what where ou guidelines and purposes.

S. Carenco, L'Actualité Chimique 2024, 496, Juillet-Août

Interview pour CNRS Le Journal (8 juillet 2019)

"La jeune garde des nanoparticules". Read Online. Read printed version. Interview réalisée par Martin Koppe.

Interview pour Innovation Review (13 septembre 2017)

"L'ERC, un outil essentiel dans le financement de la recherche fondamentale". Read Online. Interview de trois lauréats français, réalisée par Florent Detroy.

Antoine Pesesse
Master student (2018) then PhD student (2018-2021)

Rémi André
PhD student (2018-2021) then Post-Doctoral Fellow (2021-2022)

Cyprien Poucin
Master student (2019) then PhD student (2019-2022)

Alexy De Jesus Almeida Freitas
Post-Doctoral Fellow (2019-2021)

Alberto Palazzolo
Post-Doctoral Fellow (2019-2021)

Anthony Ropp
Master student (2020-2021) then PhD student (2021-2024)

Karim Azouzi
Post-doctoral fellow (2022-2024)

Kaltoum Bakkouche
Post-doctoral fellow (2023-)

Sebastian Adolfo Godoy Gutierrez
Post-doctoral fellow (2023-), co-supervized by David Loffreda at ENS Lyon.