Qu'est-ce que l'humanitaire ?

La guerre, ne paraît plus aujourd'hui possible, tout au moins dans son acceptation classique, à savoir la guerre interétatique entre armées régulières, elle ne semble plus constituer un moyen "convenable" de politique internationale, même lorsqu'il s'agit de mettre un terme à un conflit armé. La multiplication des actions dites humanitaires ou définies comme telles a coïncidé avec les transformations de la fin de la bipolarité. Certes, ce type d'actions ne constitue pas une nouveauté, il n'es..

Impact de la polémique sur la possible "relation vaccin contre l'hépatite B et la sclérose en plaques" sur la prescription et la pratique de cette vaccination par les médecins généralistes du Vaucluse

AIX-MARSEILLE2-BU Méd/Odontol. (130552103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Toward fully organic rechargeable charge storage devices based on carbon electrodes grafted with redox molecules

International audienceActivated carbon powders modified with naphthalimide and 2,2,6,6-tetramethylpiperidine-N-oxyl were assembled into a hybrid electrochemical capacitor containing an organic electrolyte. The fully organic rechargeable system demonstrated an increase in specific capacitance up to 51%, an extended operating voltage of 2.9 V in propylene carbonate, compared to 1.9 V for the unmodified system, and a power 2.5 times higher

MnO 2 Thin Films on 3D Scaffold: Microsupercapacitor Electrodes Competing with “Bulk” Carbon Electrodes

International audienceA simple, binder-free fabrication of high capacitance electrodes based on manganese dioxide (MnO2) thin films is reported. The 3D structure of these electrodes significantly improves the areal capacitance of the MnO2 thin films up to 670 mF cm−2 in aqueous electrolyte, which is 4.5 times higher than the best reported capacitance of 3D electrodes thus far. This capacitance is on the same order of magnitude as that of a bulk carbon electrode. Moreover, the 3D MnO2-based electrode exhibits a stable cycling behavior for more than 15 000 cycles

Revisiting Rb2TiNb6O18 as electrode materials for energy storage devices

International audienceIn the search of new materials for the future generation of Li-ion batteries, a look into the past has brought the multicationic oxide Rb2TiNb6O18 to the foreground. Structural characterization of this material has been carried out thanks to the combination of XRD, SEM and HRTEM highlighting the complex structure of this material. Ion exchange was performed in order to replace the rubidium ions by hydrated protons. Then, a comparative study of Rb2TiNb6O18 and the obtained proton exchanged analogues H2TiNb6O18 when used as negative electrode materials is depicted in terms of both structure and electrochemical behavior. Interestingly, while only a negligible Li+ insertion is evidenced in the rubidium phase, the H2TiNb6O18 exhibits a much higher lithium intercalation between 1 V and 3 V vs Li/Li+. A specific capacity of 118 mAh.g(-1) is reported when cycled at 0.02 A.g(-1). A solid solution type mechanism has been revealed by in situ XRD experiments. Moreover, during the lithiation, the volume of the material increases by only 1% showing the interest of this type of phase to develop "zero-strain" materials

Revisiting Rb2TiNb6O18 as electrode materials for energy storage devices

International audienceIn the search of new materials for the future generation of Li-ion batteries, a look into the past has brought the multicationic oxide Rb2TiNb6O18 to the foreground. Structural characterization of this material has been carried out thanks to the combination of XRD, SEM and HRTEM highlighting the complex structure of this material. Ion exchange was performed in order to replace the rubidium ions by hydrated protons. Then, a comparative study of Rb2TiNb6O18 and the obtained proton exchanged analogues H2TiNb6O18 when used as negative electrode materials is depicted in terms of both structure and electrochemical behavior. Interestingly, while only a negligible Li+ insertion is evidenced in the rubidium phase, the H2TiNb6O18 exhibits a much higher lithium intercalation between 1 V and 3 V vs Li/Li+. A specific capacity of 118 mAh.g(-1) is reported when cycled at 0.02 A.g(-1). A solid solution type mechanism has been revealed by in situ XRD experiments. Moreover, during the lithiation, the volume of the material increases by only 1% showing the interest of this type of phase to develop "zero-strain" materials

Unveiling Pseudocapacitive Charge Storage Behavior in FeWO4 Electrode Material by Operando X-ray Absorption Spectroscopy

In nano-sized FeWO4 electrode material, both Fe and W metal cations are suspected to be involved in the fast and reversible Faradaic surface reactions giving rise to its pseudocapacitive signature. As for any other pseudocapacitive materials, to fully understand the charge storage mechanism, a deeper insight into the involvement of the electroactive cations still has to be provided. The present paper illustrates how operando X-ray absorption spectroscopy (XAS) has been successfully used to collect data of unprecedented quality allowing to elucidate the complex electrochemical behavior of this multicationic pseudocapacitive material. Moreover, these in-depth experiments were obtained in real time upon cycling the electrode, which allowed investigating the reactions occurring in the material within a realistic timescale, which is compatible with electrochemical capacitors practical operation. Both Fe K-edge and W L3-edge measurements point out the involvement of the Fe3+/Fe2+ redox couple in the charge storage while W6+ acts as a spectator cation. The result of this study enables to unambiguously discriminate between the Faradaic and capacitive behavior of FeWO4. Beside these valuable insights toward the full description of the charge storage mechanism in FeWO4, this paper demonstrates the potential of operando X-ray absorption spectroscopy to enable a better material engineering for new high capacitance pseudocapacitive electrode materials

Unveiling Pseudocapacitive Charge Storage Behavior in FeWO 4 Electrode Material by Operando X‐Ray Absorption Spectroscopy

International audienceIn nano-sized FeWO 4 electrode material, both Fe and W metal cations are suspected to be involved in the fast and reversible Faradaic surface reactions giving rise to its pseudocapacitive signature. As for any other pseudocapacitive materials, to fully understand the charge storage mechanism, a deeper insight into the involvement of the electroactive cations still has to be provided. The present paper illustrates how operando X-ray absorption spectroscopy (XAS) has been successfully used to collect data of unprecedented quality allowing to elucidate the complex electrochemical behavior of this multicationic pseudocapacitive material. Moreover, these in-depth experiments were obtained in real time upon cycling the electrode, which allowed investigating the reactions occurring in the material within a realistic timescale, which is compatible with electrochemical capacitors practical operation. Both Fe K-edge and W L 3-edge measurements point out the involvement of the Fe 3+ /Fe 2+ redox couple in the charge storage while W 6+ acts as a spectator cation. The result of this study enables to unambiguously discriminate between the Faradaic and capacitive behavior of FeWO 4. Beside these valuable insights toward the full description of the charge storage mechanism in FeWO 4 , this paper demonstrates the potential of operando X-ray absorption spectroscopy to enable a better material engineering for new high capacitance pseudocapacitive electrode materials