Marie-Anne Dourges

Nanostructuration is one of the most promising strategies to develop performant electrode materials for energy storage devices, such as hybrid supercapacitors. In this work, we studied the influence of precipitation medium and the use of a series of 1-alkyl-3-methylimidazolium bromide ionic liquids for the nanostructuration of β(III) cobalt oxyhydroxides. Then, the effect of the nanostructuration and the impact of the different ionic liquids used during synthesis were investigated in terms of energy storage performances. First, we demonstrated that forward precipitation, in a cobalt-rich medium, leads to smaller particles with higher specific surface areas (SSA) and an enhanced mesoporosity. Introduction of ionic liquids (ILs) in the precipitation medium further strongly increased the specific surface area and the mesoporosity to achieve well-nanostructured materials with a very high SSA of 265 m²/g and porosity of 0.43 cm³/g. Additionally, we showed that ILs used as surfactant and template also functionalize the nanomaterial surface, leading to a beneficial synergy between the highly ionic conductive IL and the cobalt oxyhydroxide, which lowers the resistance charge transfer and improves the specific capacity. The nature of the ionic liquid had an important influence on the final electrochemical properties and the best performances were reached with the ionic liquid containing the longest alkyl chain.

This work explores a methodology where immobilization of square planar platinum(ii) terpyridyl luminophores onto meso/microporous silica alters the Pt(ii) electronic structure, inducing a rigidochromic behavior that is dictated by the silica porosity.

Carbon from biomass as an active material for supercapacitor electrodes has attracted much interest due to its environmental soundness, abundance, and porous nature. In this context, activated carbon prepared from coconut shells via a simple activation process (water or steam as activation agents) was used as an active material in electrodes for eco-friendly supercapacitors. X-ray diffraction (XRD), Raman spectroscopy, conductivity, scanning electron microscopy (SEM), N₂ sorption and thermogravimetry coupled to mass spectrometry (TGA-MS) studies revealed that activated carbon produced by this approach exhibit a graphitic phase, a high surface area, and large pore volume. The energy storage properties of activated carbon electrodes correlate with the morphological and structural properties of the precursor material. In particular, electrodes made of activated carbon exhibiting the largest Brunauer–Emmett–Teller (BET) surface area, i.e. 1998 m² g⁻¹, showed specific capacitance of 132.3 F g⁻¹ in aqueous electrolyte (1.5 M H₂SO₄), using expanded graphite sheets as current collector substrates. Remarkably, this sample in a configuration with ionic liquid (1-methyl-1-propy-pyrrolizinium bis(fluorosulfonyl)mide) (MPPyFSI) as electrolyte and a polyethylene separator displayed an outstanding storage capability and energy-power handling capability of 219.4 F g⁻¹ with a specific energy of 92.1 W h kg⁻¹ and power density of 2046.9 W kg⁻¹ at 1 A g⁻¹ and maintains ultra-high values at 30 A g⁻¹ indicating the ability for a broad potential of energy and power related applications. To the best of our knowledge, these values are the highest ever reported for ionic liquid-based supercapacitors with activated carbon obtained from the biomass of coconut shells.

Lightening the load: Permanent magnets are generally produced from solid metals or alloys. Less dense compositions involving lighter elements tend to demagnetize well below room temperature or under modest applied external fields. Perlepe et al. now report that chemical reduction of a low-density chromium-pyrazine network produces a magnet that remains stable above 200°C and resists demagnetization with 7500-oersted coercivity at room temperature. The straightforward synthetic route to the material shows promise for broad exploration of potential applications. Science , this issue p. 587

This paper reports on an innovative and efficient approach based on the use of ionic liquids to govern the nano-structuration of HCoO₂, in order to optimize the porosity and enhance the ionic diffusion through the electrode materials.