Time filter

Source Type

Toulouse, France

Paul Sabatier University is a French university, in the Academy of Toulouse.Founded in 1229, the University of Toulouse is one of the oldest in Europe. Today’s Toulouse III was named for Paul Sabatier, winner of the 1912 Nobel prize in chemistry, when it was established on the foundations of the old university in 1969. The Université Paul Sabatier , an educational leader in France’s Midi-Pyrénées region, offers a broad array of programs in the science, technology, health, and athletics. Wikipedia.

Augustyn V.,University of California at Los Angeles | Simon P.,University Paul Sabatier | Simon P.,CNRS RS2E | Dunn B.,University of California at Los Angeles
Energy and Environmental Science | Year: 2014

Electrochemical energy storage technology is based on devices capable of exhibiting high energy density (batteries) or high power density (electrochemical capacitors). There is a growing need, for current and near-future applications, where both high energy and high power densities are required in the same material. Pseudocapacitance, a faradaic process involving surface or near surface redox reactions, offers a means of achieving high energy density at high charge-discharge rates. Here, we focus on the pseudocapacitive properties of transition metal oxides. First, we introduce pseudocapacitance and describe its electrochemical features. Then, we review the most relevant pseudocapacitive materials in aqueous and non-aqueous electrolytes. The major challenges for pseudocapacitive materials along with a future outlook are detailed at the end. This journal is © 2014 the Partner Organisations.

Dussutour A.,University Paul Sabatier
Proceedings. Biological sciences / The Royal Society | Year: 2012

A key determinant of the relationship between diet and longevity is the balance of protein and carbohydrate in the diet. Eating excess protein relative to carbohydrate shortens lifespan in solitary insects. Here, we investigated the link between high-protein diet and longevity, both at the level of individual ants and colonies in black garden ants, Lasius niger. We explored how lifespan was affected by the dietary protein-to-carbohydrate ratio and the duration of exposure to a high-protein diet. We show that (i) restriction to high-protein, low-carbohydrate diets decreased worker lifespan by up to 10-fold; (ii) reduction in lifespan on such diets was mainly due to elevated intake of protein rather than lack of carbohydrate; and (iii) only one day of exposure to a high-protein diet had dire consequences for workers and the colony, reducing population size by more than 20 per cent.

Simon P.,University Paul Sabatier | Simon P.,CNRS RS2E | Gogotsi Y.,Drexel University
Accounts of Chemical Research | Year: 2013

Securing our energy future is the most important problem that humanity faces in this century. Burning fossil fuels is not sustainable, and wide use of renewable energy sources will require a drastically increased ability to store electrical energy. In the move toward an electrical economy, chemical (batteries) and capacitive energy storage (electrochemical capacitors or supercapacitors) devices are expected to play an important role. This Account summarizes research in the field of electrochemical capacitors conducted over the past decade.Overall, the combination of the right electrode materials with a proper electrolyte can successfully increase both the energy stored by the device and its power, but no perfect active material exists and no electrolyte suits every material and every performance goal. However, today, many materials are available, including porous activated, carbide-derived, and templated carbons with high surface areas and porosities that range from subnanometer to just a few nanometers. If the pore size is matched with the electrolyte ion size, those materials can provide high energy density. Exohedral nanoparticles, such as carbon nanotubes and onion-like carbon, can provide high power due to fast ion sorption/desorption on their outer surfaces. Because of its higher charge-discharge rates compared with activated carbons, graphene has attracted increasing attention, but graphene had not yet shown a higher volumetric capacitance than porous carbons.Although aqueous electrolytes, such as sodium sulfate, are the safest and least expensive, they have a limited voltage window. Organic electrolytes, such as solutions of [N(C2H5) 4]BF4 in acetonitrile or propylene carbonate, are the most common in commercial devices. Researchers are increasingly interested in nonflammable ionic liquids. These liquids have low vapor pressures, which allow them to be used safely over a temperature range from -50 C to at least 100 C and over a larger voltage window, which results in a higher energy density than other electrolytes.In situ characterization techniques, such as nuclear magnetic resonance (NMR), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS), and electrochemical quartz crystal microbalance (EQCM) have improved our understanding of the electrical double layer in confinement and desolvation of ions in narrow pores. Atomisitic and continuum modeling have verified and guided these experimental studies. The further development of materials and better understanding of charged solid-electrolyte interfaces should lead to wider use of capacitive energy storage at scales ranging from microelectronics to transportation and the electrical grid. Even with the many exciting results obtained using newer materials, such as graphene and nanotubes, the promising properties reported for new electrode materials do not directly extrapolate to improved device performance. Although thin films of nanoparticles may show a very high gravimetric power density and discharge rate, those characteristics will not scale up linearly with the thickness of the electrode. © 2012 American Chemical Society.

Gold A.,University Paul Sabatier
Applied Physics Letters | Year: 2010

We analyze experimental results for the mobility of the two-dimensional electron gas as realized in ZnO/MgZnO heterostructures. For zero temperature we calculate the mobility as function of the electron density for charged-impurity and for interface-roughness scattering. Multiple scattering effects, leading to a metal-insulator transition, are taken into account. The results of our calculation are in good agreement with experimental results. The numbers obtained for the parameters of interface-roughness scattering and charged-impurity scattering are reasonable. We argue that the electron gas in this heterostructure might be spin-polarized. © 2010 American Institute of Physics.

Sonke J.E.,University Paul Sabatier
Geochimica et Cosmochimica Acta | Year: 2011

Mass independent fractionation (MIF) of stable isotopes associated with terrestrial geochemical processes was first observed in the 1980s for oxygen and in the 1990s for sulfur isotopes. Recently mercury (Hg) was added to this shortlist when positive odd Hg isotope anomalies were observed in biological tissues. Experimental work identified photoreduction of aquatic inorganic divalent HgII and photodegradation of monomethylmercury species as plausible MIF inducing reactions. Observations of continental receptors of atmospheric Hg deposition such as peat, lichens, soils and, indirectly, coal have shown predominantly negative MIF. This has led to the suggestion that atmospheric Hg has negative MIF signatures and that these are the compliment of positive Hg MIF in the aquatic environment. Recent observations on atmospheric vapor phase Hg0 and HgII in wet precipitation reveal zero and positive Hg MIF respectively and are in contradiction with a simple aquatic HgII photoreduction scenario as the origin for global Hg MIF observations. This study presents a synthesis of all terrestrial Hg MIF observations, and these are integrated in a one-dimensional coupled continent-ocean-atmosphere model of the global Hg cycle. The model illustrates how Hg MIF signatures propagate through the various Earth surface reservoirs. The scenario in which marine photoreduction is the main MIF inducing process results in negative atmospheric Δ199Hg and positive ocean Δ199Hg of -0.5‰ and +0.25‰, yet does not explain atmospheric Hg0 and HgII wet precipitation observations. Alternative model scenarios that presume in-cloud aerosol HgII photoreduction and continental HgII photoreduction at soil, snow and vegetation surfaces to display MIF are necessary to explain the ensemble of natural observations. The model based approach is a first step in understanding Hg MIF at a global scale and the eventual incorporation of Hg stable isotope information in detailed global mercury chemistry and transport models. © 2011 Elsevier Ltd.

Discover hidden collaborations