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Monini V, Bonechi M, Bazzicalupi C, Bianchi A, Gentilesca P, Giurlani W, Innocenti M, Meoli A, Romano GM, Savastano M. Oxygen reduction reaction (ORR) in alkaline solution catalysed by an atomically precise catalyst based on a Pd(II) complex supported on multi-walled carbon nanotubes (MWCNTs). Electrochemical and structural considerations. Dalton Trans 2024; 53:2487-2500. [PMID: 38193252 DOI: 10.1039/d3dt03947a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
A new atomically precise, single-ion catalyst (MWCNT-LPd) for ORR (oxygen reduction reaction), consisting of a Pd(II) complex of a tetraazacycloalkane anchored on multiwalled carbon nanotubes, has been prepared through a supramolecular approach ensuring a uniform distribution of catalytic centres on the support surface. A tetraazacycloalkane was chosen to saturate the four coordination sites of the typical square planar coordination geometry of Pd(II) with the aim of ascertaining whether the metal ion must have free coordination sites to function effectively in the ORR or whether, as predicted by quantum mechanical calculations, the catalytic effect can be originated from an interaction of O2 in the fifth coordinative position. The results clearly demonstrated that tetracoordination of Pd(II) does not influence its catalytic capacity in the ORR. Electrodes based on this catalyst show ORR performance very close to that of commercial Pt electrodes, despite the low Pd(II) content (1.72% by weight) in the catalyst. The onset potential (Eon) value and the half-wave potential (E1/2) of the catalyst are, respectively, only 53 mV and 24 mV less positive than those observed for the Pt electrode and direct conversion of O2 to H2O reaches 85.0%, compared to 89% of the Pt electrode. Furthermore, a preliminary galvanostatic test (simulating a working fuel cell at a fixed potential) showed that the catalyst maintains its efficiency continuing to produce water throughout the process (the average number of electrons exchanged over time per O2 molecule remains close to 4).
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Affiliation(s)
- Valeria Monini
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy.
| | - Marco Bonechi
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy.
| | - Carla Bazzicalupi
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy.
| | - Antonio Bianchi
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy.
- National Interuniversity Consortium of Materials Science and Technology (INSTM), Research Unit of Florence, Via G. Giusti 9, 50121 Florence, Italy.
| | - Pietro Gentilesca
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy.
| | - Walter Giurlani
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy.
| | - Massimo Innocenti
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy.
- National Interuniversity Consortium of Materials Science and Technology (INSTM), Research Unit of Florence, Via G. Giusti 9, 50121 Florence, Italy.
| | - Arianna Meoli
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy.
| | - Giammarco Maria Romano
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy.
| | - Matteo Savastano
- National Interuniversity Consortium of Materials Science and Technology (INSTM), Research Unit of Florence, Via G. Giusti 9, 50121 Florence, Italy.
- Department of Human Sciences for the Promotion of Quality of Life, University San Raffaele Roma, Via di Val Cannuta 247, 00166 Rome, Italy
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Valbuena-Rus AM, Savastano M, Arranz-Mascarós P, Bazzicalupi C, Clares MP, Godino-Salido ML, Gutiérrez-Valero MD, Inclán M, Bianchi A, García-España E, López-Garzón R. Noncovalent Assembly and Catalytic Activity of Hybrid Materials Based on Pd Complexes Adsorbed on Multiwalled Carbon Nanotubes, Graphene, and Graphene Nanoplatelets. Inorg Chem 2022; 61:12610-12624. [PMID: 35926979 PMCID: PMC9387097 DOI: 10.1021/acs.inorgchem.2c01559] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Green catalysts with excellent performance in Cu-free
Sonogashira
coupling reactions can be prepared by the supramolecular decoration
of graphene surfaces with Pd(II) complexes. Here we report the synthesis,
characterization, and catalytic properties of new catalysts obtained
by the surface decoration of multiwalled carbon nanotubes (MWCNTs),
graphene (G), and graphene nanoplatelets (GNPTs) with Pd(II) complexes
of tetraaza-macrocyclic ligands bearing one or two anchor functionalities.
The decoration of these carbon surfaces takes place under environmentally
friendly conditions (water, room temperature, aerobic) in two steps:
(i) π–π stacking attachment of the ligand via electron-poor
anchor group 6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxo-pyrimidine
and (ii) Pd(II) coordination from PdCl42–. Ligands are more efficiently adsorbed on the flat surfaces of G
and GNPTs than on the curved surfaces of MWCNTs. All catalysts work
very efficiently under mild conditions (50 °C, aerobic, 7 h),
giving a similar high yield (90% or greater) in the coupling of iodobenzene
with phenylacetylene to form diphenylacetylene in one catalytic cycle,
but catalysts based on G and GNPTs (especially on GNPTs) provide greater
catalytic efficiency in reuse (four cycles). The study also revealed
that the active centers of the ligand-Pd type decorating the support
surfaces are much more efficient than the Pd(0) and PdCl42– centers sharing the same surfaces. All of the
results allow a better understanding of the structural factors to
be controlled in order to obtain an optimal efficiency from similar
catalysts based on graphene supports. Green catalysts
with high efficiency in the Cu-free Sonogashira
C−C coupling reactions can be prepared by the supramolecular
functionalization of carbon materials.
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Affiliation(s)
- Alba M Valbuena-Rus
- Department of Inorganic and Organic Chemistry, University of Jaén, 23071 Jaen, Spain
| | - Matteo Savastano
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy.,National Interuniversity Consortium of Materials Science and Technology (INSTM), Via G. Giusti 9, 50121 Florence, Italy
| | | | - Carla Bazzicalupi
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy
| | - María P Clares
- ICMol, Department of Inorganic Chemistry, University of Valencia, C/Catedrático José Beltrán 2, 46980 Paterna, Spain
| | - María L Godino-Salido
- Department of Inorganic and Organic Chemistry, University of Jaén, 23071 Jaen, Spain
| | | | - Mario Inclán
- ICMol, Department of Inorganic Chemistry, University of Valencia, C/Catedrático José Beltrán 2, 46980 Paterna, Spain
| | - Antonio Bianchi
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy
| | - Enrique García-España
- ICMol, Department of Inorganic Chemistry, University of Valencia, C/Catedrático José Beltrán 2, 46980 Paterna, Spain
| | - Rafael López-Garzón
- Department of Inorganic and Organic Chemistry, University of Jaén, 23071 Jaen, Spain
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Savastano M, Boscaro F, Bianchi A. Metal Coordination Properties of a Chromophoric Desferrioxamine (DFO) Derivative: Insight on the Coordination Stoichiometry and Thermodynamic Stability of Zr 4+ Complexes. Molecules 2021; 27:molecules27010184. [PMID: 35011419 PMCID: PMC8746621 DOI: 10.3390/molecules27010184] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 12/21/2021] [Accepted: 12/22/2021] [Indexed: 11/16/2022] Open
Abstract
Desferrioxamine (DFO) is the current "gold standard" chelator for 89Zr4+, which is used to label monoclonal antibodies for applications in immunopositron emission tomography. Recently, controversial data have been reported regarding the speciation and the stability of the complexes formed by DFO with Zr4+ in solution. To shed some light on this point, we studied the coordination properties in solution ofa chromophoric DFO derivative bearing a substituted pyrimidine residue (DFO-Pm) toward several metal ions (Zr4+, Cu2+, Zn2+, Mg2+, Ca2+, Na+, K+). Potentiometric titrations showed that DFO-Pm and pristine DFO form complexes with very similar stoichiometry and stability. DFO-Pm, which can consequently be taken as a model system for DFO, provides a photochemical response to metal coordination that can be used to further define the complexes formed. In the critical case of Zr4+, spectrophotometric measurements allowed the verification of the formation of 1:1 and 2:3 complexes that, together with 2:2 complexes form the coordination model that was obtained through the use of our potentiometric measurements. Additionally, mass spectrometry measurements verified the formation of 1:1 and 2:3 complexes and showed that 1:2 species can be easily generated through the fragmentation of the 2:3 species. In conclusion, the results obtained with DFO-Pm validate the complexation model of Zr4+/DFO composed of 1:1, 2:2, and 2:3 metal-to-ligand complexes. Convergences and conflicts with other works are addressed.
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Affiliation(s)
- Matteo Savastano
- Department of Chemistry “Ugo Schiff”, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy;
- Correspondence:
| | - Francesca Boscaro
- Centro Interdipartimentale di Spettrometria di Massa (CISM), University of Florence, Viale G. Pieraccini 6, 50139 Florence, Italy;
| | - Antonio Bianchi
- Department of Chemistry “Ugo Schiff”, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy;
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On the Oxygen Reduction Reaction Mechanism Catalyzed by Pd Complexes on 2D Carbon. A Theoretical Study. Catalysts 2021. [DOI: 10.3390/catal11070764] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Oxygen Reduction Reaction (ORR) is the bottle-neck strategic reaction ruling the fuel cell efficiency process. The slow kinetics of the reaction require highly effective electrocatalysts for proper boosting. In this field, composite catalysts formed by carbon nanotubes functionalized with palladium(II) complexes showed surprising catalytic activity comparable to those of a commercial Pt electrode, but the catalytic mechanisms of these materials still remain open to discussion. In this paper, we propose the combination of experimental and theoretical results to unfold the elementary reaction steps underlying the ORR catalysis.
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Savastano M, Passaponti M, Giurlani W, Lari L, Calisi N, Delgado-Pinar E, Serrano ES, Garcia-España E, Innocenti M, Lazarov VK, Bianchi A. Linear, tripodal, macrocyclic: Ligand geometry and ORR activity of supported Pd(II) complexes. Inorganica Chim Acta 2021. [DOI: 10.1016/j.ica.2021.120250] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Multi-Walled Carbon Nanotubes Supported Pd(II) Complexes: A Supramolecular Approach towards Single-Ion Oxygen Reduction Reaction Catalysts. ENERGIES 2020. [DOI: 10.3390/en13215539] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Lowering the platinum group metal content of oxygen reduction reaction catalysts is among the most prevalent research focuses in the field. This target is herein approached through supported Pd(II) complexes. Starting from a commercial macrocycle, a new ligand is synthesized, its solution behavior and binding properties briefly explored (potentiometry, UV-Vis) and then used to prepare a new catalyst. A supramolecular approach is used in order to obtain homogeneous decoration of carbon nanotubes surfaces, fostering novel possibilities to access single-ion active sites. The novel catalyst is characterized through X-ray photoelectron spectroscopy and scanning transmission electron microscopy and its promising oxygen reduction reaction performance is evaluated via rotating ring-disk electrode and rotating disk electrode in half-cell studies.
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