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Madec, L., Robert, D., Moreau, P., Bayle-Guillemaud, P., Guyomard, D. & Gaubicher, J. (2013) Synergistic Effect in Carbon Coated LiFePO4 for High Yield Spontaneous Grafting of Diazonium Salt. Structural Examination at the Grain Agglomerate Scale. J. Am. Chem. Soc. 135 11614–11622.
Added by: Laurent Cournède (2016-03-10 21:23:30) |
| Type de référence: Article DOI: 10.1021/ja405087x Numéro d'identification (ISBN etc.): 0002-7863 Clé BibTeX: Madec2013 Voir tous les détails bibliographiques  |
Catégories: ST2E Mots-clés: aryldiazonium salts, chemical-modification, covalent modification, domino-cascade model, electrochemical reduction, glassy-carbon, nitrophenyl groups, organic layers, redox functionalization, Surface modification Créateurs: Bayle-Guillemaud, Gaubicher, Guyomard, Madec, Moreau, Robert Collection: J. Am. Chem. Soc. |
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Molecular grafting of p-nitrobenzene diazonium salt at the surface of (Li)FePO4-based materials was thoroughly investigated. The grafting yields obtained by FTIR, XPS, and elemental analysis for core shell LiFePO4-C are found to be much higher than the sum of those associated with either the LiFePO4 core or the carbon shell alone, thereby revealing a synergistic effect. Electrochemical, XRD, and EELS experiments demonstrate that this effect stems from the strong participation of the LiFePO4 core that delivers large amounts of electrons to the carbon substrate at a constant energy, above the Fermi level of the diazonium salt. Correspondingly large multilayer anisotropic structures that are associated with outstanding grafting yields could be observed from TEM experiments. Results therefore constitute strong evidence of a grafting mechanism where homolytic cleavage of the N-2(+) species occurs together with the formation and grafting of radical nitro-aryl intermediates. Although the oxidation and concomitant Li deintercalation of LiFePO4 grains constitute the main driving force of the functionalization reaction, EFTEM EELS mapping shows a striking lack of spatial correlation between grafted grains and oxidized ones.
Added by: Laurent Cournède |