Matthieu Becuwe

Pseudocapacitance and excellent cyclability of 2,5-dimethoxy-1,4-benzoquinone on graphene

Electrochemically active organic materials are emerging as low cost, naturally abundant and sustainable alternatives to their metal-based counterparts. However, their usage in energy storage systems is mainly hindered by their poor conductivity, which results in capacitance fade upon cycling. Here, we report a redox-active xerogel composed of 2,5-dimethoxy-1,4-benzoquinone (DMQ) decorated on reduced graphene oxide (rGO) sheets via a hydrothermal method as a high capacitance and long cycle life pseudocapacitive electrode. DMQ not only provided stable redox-active centers but also served as a spacer to avoid rGO sheets aggregation and led to a three-dimensional (3D) hierarchical electrode architecture. When a binder-free 50 μm thick rolled film was tested as a pseudocapacitive electrode, it exhibited an excellent capacitance of 650 F g−1 at 5 mV s−1 (780 F cm−3) in 1 M sulfuric acid, outperforming a large number of reported organic and inorganic electrodes. Most importantly, optimized electrodes showed an excellent capacitance retention of 99% after 25000 cycles at 50 mV s−1. Density functional theory (DFT) calculations are further used to understand the charge storage mechanism, the preferred orientation of the adsorbed molecules, charge density distribution and density of states. Our combined experimental and theoretical findings demonstrate that the careful selection of the conductive substrate, electrode architecture and organic molecules plays a crucial role in achieving high capacitance and long cycling performance.

Hyper-conjugated lithium carboxylate based on a perylene unit for high-rate organic lithium-ion batteries

A high-rate cycling lithium carboxylate-based organic anode material using perylene core as a platform for stabilization is described. The hyper-conjugated core unit of perylene associated with lithium carboxylate confers the electrode an outstanding rate capability without any electrode formulation engineering, maintaining over 120 mA h g−1 gravimetric capacity after one hundred cycles at 5 Li+/1 h rate.

A new sensitive organic/inorganic hybrid material based on titanium oxide for the potentiometric detection of iron(III)

The formation of a new hybrid material based on titanium dioxide as inorganic support and containing an iron organochelator (ICL670) is described. An organophosphorous coupling agent was used to graft the organic molecule on the oxide surface. The attachment of the organic substrate was well-confirmed by FTIR (DRIFT), solid-state (31)P and (13)C CPMAS NMR, thermal analysis and the integrity of the structural and morphological parameters were verified using XRD and TEM analyses. The interaction between the material and dissolved iron(III) was also investigated through potentiometric measurements and demonstrated the interest of this new non-siliceous based hybrid material. The obtained linear evolution of the open circuit potential from 10(-2) to 10(-6) mol L(-1) can be used for the analytical detection of iron(III).

Immobilization of fluorescent chemosensor on pyrogenic silica: A promising device for gaseous detection

A new approach to enhance performances of a cyclodextrin-based fluorescent chemosensor combining grafting on a silica matrix and quaternization reaction is presented. The full characterization of new fluorescent hybrid material has clearly revealed the embedding of cyclodextrin inside the siliceous material. Finally, through a comparison with previous aqueous studies, a preliminary test of toluene detection was presented and highlighted the high potential of this approach, which opens attractive perspectives of evolution toward more sensitive and selective VOCs sensing in air or in hot industrial gaseous waste.

An air-stable lithiated cathode material based on a 1,4-benzenedisulfonate backbone for organic Li-ion batteries

To meet current market demands as well as emerging environmental concerns there is a need to develop less polluting battery technologies. Organic electrode materials could offer the possibility of preparing electrode materials from naturally more abundant elements and eco-friendly processes coupled with simplified recycling management. However, the potential use of organic electrode materials for energy storage is still challenging and a lot of developments remain to be achieved. For instance, promoting high-energy Li-ion organic batteries inevitably requires the development of lithiated organic electrode materials which are able to be charged (delithiated) at a high enough potential (>3 V vs. Li+/Li0) – a challenging point rarely discussed in the literature. Here, we evaluate tetralithium 2,5-dihydroxy-1,4-benzenedisulfonate as an air-stable lithiated cathode material for the first time and its reversible Li+ electrochemical extraction. Quite interestingly, in comparison with the dicarboxylate counterpart, it was observed that the theoretical two-electron reaction is readily reached with this organic structure and at an average operating potential of 650 mV higher.

Nitroxide supported on nanometric metal oxides as new hybrid catalysts for selective sugar oxidation

A new series of supported organocatalysts, prepared by a simple method, were used for selective sugar oxidation. This approach is based on the immobilization of a nitroxide derivative through a carboxylic function on nanometric metal oxides (TiO2, Al2O3 and CeO2), allowing the recovery of the catalyst. These hybrid materials were carefully characterized by Diffuse Reflectance FT-IR spectroscopy (DRIFT), ThermoGravimetric Analysis (TGA), X-Ray Diffraction (XRD), Brunauer-Emmet-Teller surface area measurements (B.E.T.), elemental and electrochemical analyses, showing different characteristics and behaviors depending on the nature of the metal oxide used. The activity of the supported nitroxide catalyst was evaluated on methyl α-d-glucoside oxidation, used as model reaction. In all cases, high catalytic activity was highlighted, with up to 25 times less nitroxyl radical required for complete conversion than under homogeneous conditions. The influence of several experimental conditions such as the use of phosphate buffer and recyclability of the catalyst were also investigated.

Relating Electrochemistry of New Organic Materials for Batteries and Fundamental Understanding through DFT Calculations

We present DFT investigations on the redox properties of quinone based precursors exhibiting growing interest from the electrochemists community due to their potential application as electrodes for new battery devices, with lower ecological footprint. A screening of various substituents is undertaken with the aim of providing guidelines to the experimentalists towards most promising candidates. A comparison of the effect of aromaticity extension is provided through the comparison of 1,4-benzo-/naphtho-/anthra-quinone and 9,10-anthraquinone backbones. Additionally, this work allowed the establishment of a ranking and quantitative assessment of substituents with respect to both increase and decrease of the redox voltage (useful for positive and negative electrodes, respectively) by considering such functionalizing groups for the monosubstitution of the 1,4-benzoquinone. Our computational work elucidates important fundamental relationships between redox voltage and local chemical bonding features, which may serve to the comprehension and design of new organic electrodes.

Poly[μ6-(naphthalene-2,6-di-carboxyl-ato)-bis-(aqua-lithium)].

The title compound, [Li2(C12H6O4)(H2O)2]n, crystallizes with one half of the molecular entities in the asymmetric unit. The second half is gererated by inversion symmetry. The crystal structure has a layered arrangement built from distorted edge-sharing LiO3(OH)2 tetrahedra parallel to (100), with naphthalenedicarboxylate bridging the LiO3(OH)2 layers along the [100] direction. Hydrogen bonding between the water molecule and adjacent carboxylate groups consolidates the packing.