Two-dimensional neutron scattering in a floating heavy water bridge

International audienceWhen high voltage is applied to pure water filled into two beakers close to each other, a connection forms spontaneously, giving the impression of a floating water bridge. This phenomenon is of special interest, since it comprises a number of phenomena currently tackled in modern water science. In this work, the first two dimensional structural study of a floating heavy water bridge is presented as a function of the azimuthal angle. A small anisotropy in the angular distribution of the intensity of the first structural peak was observed, indicating a preferred orientation of a part of the D 2 O molecules along the electric field lines without breaking of the local tetrahedral symmetry. The experiment is carried out by neutron scattering on a D 2 O bridge

Ag-Mn_xO_y on Graphene Oxide Derivatives as Oxygen Reduction Reaction Catalyst in Alkaline Direct Ethanol Fuel Cells

In this study, Ag-MnxOy/C composite catalysts deposited on reduced graphene oxide (rGO) and, for the first time on N-doped graphene oxide (NGO), were prepared via a facile synthesis method. The influence of the carbon support material on the activity and stability of the oxygen reduction reaction (ORR) and on the tolerance to ethanol in alkaline medium was focused and investigated. The physicochemical properties of the Ag-MnxOy/C catalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET) method, atomic absorption spectroscopy (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and thermogravimetric gas analysis (TGA). Electrochemical characterization was performed by rotating disk electrode (RDE) experiments. The results show that the active manganese species MnO2 was assembled as nanorods and nanospheres on rGO and NGO, respectively. Ag was assumed to be present as very small or amorphous particles. Similar redox processes for Ag-MnxOy/rGO and Ag-MnxOy/NGO were examined via cyclic voltammetry. The Ag-MnxOy/rGO resulted in a more negative diffusion limiting current density of −3.01 mA cm−2 compared to Ag-MnxOy/NGO. The onset potential of approximately 0.9 V vs. RHE and the favored 4-electron transfer pathway were independent of the support material. Ag-MnxOy/NGO exhibited a higher ORR stability, whereas Ag-MnxOy/rGO showed a better ethanol tolerance

Ag-MnxOy on Graphene Oxide Derivatives as Oxygen Reduction Reaction Catalyst in Alkaline Direct Ethanol Fuel Cells

In this study, Ag-MnxOy/C composite catalysts deposited on reduced graphene oxide (rGO) and, for the first time on N-doped graphene oxide (NGO), were prepared via a facile synthesis method. The influence of the carbon support material on the activity and stability of the oxygen reduction reaction (ORR) and on the tolerance to ethanol in alkaline medium was focused and investigated. The physicochemical properties of the Ag-MnxOy/C catalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET) method, atomic absorption spectroscopy (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and thermogravimetric gas analysis (TGA). Electrochemical characterization was performed by rotating disk electrode (RDE) experiments. The results show that the active manganese species MnO2 was assembled as nanorods and nanospheres on rGO and NGO, respectively. Ag was assumed to be present as very small or amorphous particles. Similar redox processes for Ag-MnxOy/rGO and Ag-MnxOy/NGO were examined via cyclic voltammetry. The Ag-MnxOy/rGO resulted in a more negative diffusion limiting current density of −3.01 mA cm−2 compared to Ag-MnxOy/NGO. The onset potential of approximately 0.9 V vs. RHE and the favored 4-electron transfer pathway were independent of the support material. Ag-MnxOy/NGO exhibited a higher ORR stability, whereas Ag-MnxOy/rGO showed a better ethanol tolerance

Thermal in Situ and System-Integrated Regeneration Strategy for Adsorptive On-Board Desulfurization Units

This work deals with the introduction and investigation of a novel system-integrated thermal regeneration strategy based on hot off-gas for on-board desulfurization units. A highly thermally stable Ag–Al₂O₃ material was used as the adsorbent because it has the advantage of being active in the oxidized form so that it requires no activation after regeneration in an oxidative atmosphere. Dibenzothiophene (DBT) was used as the representative polycyclic aromatic sulfur heterocycle (PASH) in Jet A-1 fuel with a total sulfur concentration of 900 ppmw. This PASH has a stronger adsorption energy and is significantly more stable than benzothiophene or thiophene. This is why oxidative thermal regeneration strategies had formerly been failing to fully regenerate any type of adsorbent after the adsorption of DBT. This work reports excellent regeneration results upon the use of the hot off-gas from a solid-oxide-fuel-cell- (SOFC-) driven auxiliary power unit (APU) as the regeneration medium. The highly thermally stable Ag–Al₂O₃ showed a high breakthrough adsorption capacity of 2.2 mg-S/g-adsorbent in the first desulfurization cycle that was fully recovered by regeneration with hot APU off-gas. This is the first time that 100% regeneration has been reported for thermal regeneration after the adsorption of DBT. Additional investigations were performed to gain deeper insight into the overall desorption mechanism. The H₂O content has an especially significant influence on the overall desorption mechanism of DBT. With a H₂O content of 12.4 mol %, full regeneration was also obtained by reducing the final regeneration temperature from 525 to 450 °C. The results reported herein show that this novel regeneration strategy requires no additional regeneration medium, no additional tanks, and no additional bulky equipment and is thus fully integrated into the concept of an SOFC-operated APU

Density-dependent microbial calcium carbonate precipitation by drinking water bacteria via amino acid metabolism and biosorption

Drinking water plumbing systems appear to be a unique environment for microorganisms as they contain few nutrients but a high mineral concentration. Interactions between mineral content and bacteria, such as microbial calcium carbonate precipitation (MCP) however, has not yet attracted too much attention in drinking water sector. This study aims to carefully examine MCP behavior of two drinking water bacteria species, which may potentially link scaling and biofouling processes in drinking water distribution systems. Evidence from cell density evolution, chemical parameters, and microscopy suggest that drinking water isolates can mediate CaCO3 precipitation through previously overlooked MCP mechanisms like ammonification or biosorption. The results also illustrate the active control of bacteria on the MCP process, as the calcium starts to concentrate onto cell surfaces only after reaching a certain cell density, even though the cell surfaces are shown to be the ideal location for the CaCO3 nucleation