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An elementary kinetic model was developed to predict the electrochemical response of porous LSCF and LSCF-CGO electrodes. The model was validated thanks to experiments performed on symmetrical cells using a three-electrode setup. After the model calibration on polarization curves, it has been shown that the model is able to simulate accurately the experimental impedance diagram at OCP and under polarization without additional fitting. Moreover, the evolution of the electrode polarization resistance with the oxygen partial pressure is well reproduced by the model. The electrodes reaction mechanism was thoroughly analyzed and it has been shown that the transition from the bulk path to the surface path depends on the temperature, the polarization and the oxygen partial pressure. The rate-determining steps for the LSCF electrode have been identified at OCP as function of the oxygen partial pressure. Finally, a sensitivity analysis has been performed to study the impact of LSCF demixing on the electrode performances. For a given decomposition, it has been highlighted that the surface passivation would be more impacting than the decrease of the ionic conductivity. Moreover, the impact of the LSCF decomposition would be more detrimental for the electrode performances evaluated in electrolysis mode. [ABSTRACT FROM AUTHOR]

Reversible high temperature solid oxide cells (rSOC) can be operated both in the fuel cell (SOFC) and the electrolysis mode (SOEC). This specificity is a promising way to either store intermittent renewable energy surpluses by producing H2, or generate electricity from H2 or any other fuel locally available (CH4, biogas) when demand overtakes the local production. Therefore, rSOC technology could reinforce autonomy and flexibility in buildings, eco‐districts, up to industrial sites and local energy grids powered by intermittent renewable energies. Such a storage solution complements batteries, displays flexible energy storage durations, from a few hours up to seasonal cycles, and allows decorrelating power and storage capacity. Nonetheless, experiments are needed to assess whether rSOC systems can accommodate the surrounding environment and switch rapidly between various power levels and operating modes. An rSOC system has been built and its ability to operate in both electrolysis and fuel cell modes has been demonstrated. The present work is focused on transitioning between 3 operating modes (SOEC, SOFC operated in H2, SOFC operated in CH4), each displaying 3 power levels. The results show that all transition cycles could be done in 3 to 10 min without negatively affecting short term stack performances. [ABSTRACT FROM AUTHOR]

This work details an in-house 2D electrochemical and thermal model of solid oxide electrolysis cell (SOEC) dedicated to the simultaneous electrolysis of steam and carbon dioxide. The apparent exchange current densities for both H2O and CO2 electrochemical reductions have been fitted on single electrolysis polarization curves obtained on a standard cathode supported cell (CSC). By using these values, predictive simulations have been performed in a co-electrolysis mode. The results have been compared to experimental data obtained in the same conditions. A good agreement is found between the simulated points and the experimental polarization curves, meaning that the model stands to predict accurately the SOEC response in co-electrolysis mode. Simulations have been performed to investigate co-electrolysis mechanisms in terms of partial pressures, current densities, and overpotentials distributions along the cell. The relative influence of both water gas shift (WGS) reaction and CO2 electrolysis on the global CO production is also discussed. [ABSTRACT FROM AUTHOR]

High temperature steam electrolysis (HTSE) is one of the most promising ways for hydrogen mass production. If coupled to a CO2-free electricity and a low cost heat source, this process is liable to a high efficiency. High levels of performance and durability, in association with cost-effective stack and system components are the key points. To reach such goals, a low-weight stack has been designed, keeping the advantages of the high performing and robust stack previously validated in terms of performance, durability, and cyclability [1], but aiming at reducing the cost by the use of thin interconnects. This low-weight stack has demonstrated at the scale of a 3-cell stack a good performance of -1.0 A cm-2 at 1.3 V at 800 °C. Before performing the durability test, preliminary studies at the cell level have been carried out to highlight the effect of two major operating parameters that are the current density and the steam conversion (SC) ratio, those studies being carried out at one temperature, 800 °C. Based on these results, optimized operating parameters have been defined to perform the durability test on the stack, that is -0.5 A cm-2 and a SC ratio of 25%. Degradation rates around 3-4% 1,000 h-1 have been measured. The thermal cyclability of this stack has also been demonstrated with one thermal cycle. Therefore it can be concluded that these results make HTSE technology getting closer to the objectives of performance, durability, thermal cyclability, and cost. [ABSTRACT FROM AUTHOR]

The present study is focused on alternative structured oxygen electrodes for solid oxide electrolysis cells (SOEC). The Ln2NiO4+δ (Ln = La or Pr) nickelate oxides were selected as innovative electrode materials with respect to their mixed electronic and ionic conductivity. A thin interfacial ceria-based layer was added in between the electrode and the zirconia-based electrolyte to improve mechanical and electrochemical properties and to limit the chemical reactivity. These structured cells were characterized by electrochemical impedance spectroscopy on symmetrical cells, under zero dc conditions and anodic polarization. Low polarization resistance RP and improved anodic overpotential ηA versus current density curves were obtained for the Pr2NiO4+δ electrode with Ce0.8Y0.2O2-δ interlayer: RP is decreased down to 0.06 Ω cm2 at 800 °C, under air and zero dc conditions. Then, complete hydrogen electrode-supported cells including Pr2NiO4+δ as oxygen electrode were electrochemically characterized. At 800 °C, when the inlet gas composition is 90 vol.% H2O-10 vol.% H2 at the hydrogen electrode, air being swept at the oxygen electrode, the current density determined at 1.28 V reaches -0.9 A cm-2, the corresponding steam to hydrogen conversion ratio being 58%. These results are compared to those obtained with a reference cell including the oxygen deficient perovskite La0.6Sr0.4Fe0.8Co0.2O3-δ as oxygen electrode. [ABSTRACT FROM AUTHOR]

A theoretical investigation was carried out on the retention and separation of enantiomeric molecules including nonsteroidal anti-inflammatory drugs, anti-neoplastic compounds and N -derivatized amino acids by capillary electrophoresis using macrocyclic antibiotics, a new class of chiral selectors, as stationary phase. Firstly docking methods were used to study the enantiorecognition in chiral electrophoresis. The molecular dynamics simulations of the two diastereoisomer complexes were then performed in order to understand how these antibiotics recognize the enantiomers. Another approach was applied in this study to establish a quantitative structure-enantioselectivity relationship (QSER) model, able to describe the resolution of a series of chiral compounds in capillary electrophoresis using vancomycin as the resolving agent. [ABSTRACT FROM AUTHOR]

In this paper a new chemoinformatics tool for Molecular Diversity Analysis (MolDIA) is introduced. The objective of this system is the analysis of molecular similarity and diversity through the treatment of structural and physicochemical information. Current needs for chemical databases include the analysis, the management and the retrieval of chemical information. The implementation of eXtended Markup Languages (XML) is proposed as a basis for representing and structuring the chemical information contained in data structures and databases. The adequate descriptor vector and related physicochemical properties have been defined and constructed. The benefits of XML in chemoinformatics are discussed, as well as, the applications of this system in a virtual screening environment. [ABSTRACT FROM AUTHOR]

Abstract: The oxygen transport properties in (La0.8Sr0.2)(Mn1−y Fe y )O3±δ (LSMF) with various iron contents y =0, 0.2, 0.5, 0.8 and 1 were determined by the IEDP technique. Both oxygen diffusion and surface exchange coefficients were found to be greater for y =0.8 and 1 than those of LSM (y =0). Moreover, for y ≤0.5, grain boundary diffusion was the rate limiting step especially at lower temperatures. Thus, in the LSMF perovskite materials, the oxygen diffusion via oxygen vacancies is enhanced by Fe. The LSMF electrical performances were measured by impedance spectroscopy. Compared to LSM and LSF (y =1), porous LSMF cathodes with y =0.2–0.8 exhibit poor electronic conductivity: Fe, by reducing the number of couples Mn3+/Mn4+, decreases the amount of available hopping sites, limiting the electrical conduction. For LSF, the charge disproportionation Fe3+/Fe5+ improves the electrical properties. In conclusion, only the LSMF compounds with y ∼1 or 0 can be considered as good cathode materials for SOFC applications. [Copyright &y& Elsevier]

Study design: Prospective, randomized clinical trial.SETTING:: France. OBJECTIVES:: To evaluate the safety and effect on neurological outcome of nimodipine, methylprednisolone, or both versus no medical treatment in spinal-cord injury during the acute phase. METHOD:: One hundred and six patients who had spinal trauma (including 48 with paraplegia and 58 with tetraplegia) were randomly separated into four groups: M=methylprednisolone (30 mg·kg-1 over 1 h, followed by 5.4 mg·kg-1·h-1 for 23 h), N=nimodipine (0.015 mg·kg-1·h-1 for 2 h followed by 0.03 mg·kg-1·h-1 for 7 days), MN (both agents) or P (neither medication). Neurological assessment (ASIA score) was performed by a blinded senior neurologist before treatment and at 1-year follow-up. Early spinal decompression and stabilization was performed as soon as possible after injury. RESULTS:: One hundred patients were reassessed at 1 year. Neurological improvement was seen in each group (P<0.0001), however no additional neurological benefit from treatment was observed. Infectious complications occurred more often in patients treated with M. Early surgery (49 patients underwent surgery within 8 h of their accident) did not influence the neurological outcome. The only predictor of the latter was the extent of the spinal injury (complete or incomplete lesion). CONCLUSION:: The present study confirms the absence of benefit of pharmacological therapy in this indication. Because of the paucity of clinical studies that demonstrate the efficacy of pharmacological treatment in spinal injury during the acute phase, systematic use of pharmaceutical agents should be reconsidered.Spinal Cord (2000) 38, 71–75. [ABSTRACT FROM AUTHOR]