Voltammetry of Microparticles and in situ microRaman measurements under potentiostatic conditions. I. Spectroelectrochemical behaviour of Prussian blue, PbO and Bi 2 O 3

International audienceThe results obtained with solid electroactive microparticles immobilized on a graphite electrode surface using cyclic voltammetry and in situ microRaman measurements at selected potentials allowed us to complete the understanding of the spectroelectrochemical behaviours of Prussian blue, β-PbO and Bi2O3. In the case of Prussian blue, we provided a simple but complete analysis of the Raman spectral data for the species Fe[Fe(CN)6] and K2Fe[Fe(CN)6]. The investigation of PbO in neutral chloride media showed that Pb(OH)Cl is the Pb° electrochemical oxidation product whereas the study of Bi2O3 demonstrated that the oxidation of Bi° in alkaline solutions leads essentially to amorphous Bi(OH)3

Submersible Dielectric Probe for In Situ Monitoring of Suspensions and Its Application to Activated Sludge in Waste Water Treatment Plant

International audienceWe have developed a useful dielectric probe that allows real-time and in situ characterization of suspensions in the 0.4 to 10 MHz frequency range. It has been successfully tested throughout several weeks to monitor activated sludge of a waste water treatment plant. In this paper the results are compared with those obtained in parallel using both static or flow classic dielectric cells

Voltammetry of MicroParticles in Thin Layer

International audienceWe describe a new experimental device for the characterization of electroactive microparticles and of the soluble species released during their electrochemical transformation. By using only a few microparticles, it provides, in a faster way, similar information as modified carbon paste electrodes with electrolytic binders (CPEEBs) and the sensitivity and resolution are must better. The device geometry was modelled with ferrocyanide ions and the voltammograms for ferrocene, pyrolusite and hematite were compared with the literature ones concerning CPEEBs. Finally, an alumina-supported palladium catalyst and pyrite-containing argillite were successfully characterized

Electron transfers in graphitized HZSM-5 zeolites

International audienceIn the present work, we report the electron transfers occurring after ionization of the guest molecules of t-stilbene incorporated in graphitized HZSM-5 zeolites and we compare these results with the data obtained previously for graphite-free zeolites. Complementary diffuse reflectance UV-vis and Raman scattering spectroscopies provide evidence for stabilization of long lived charge separated states as observed in non-graphitized ZSM-5. The spectral features indicate that these species are located in the channels of the zeolite structure. However, the pulsed EPR technique shows strong coupling between unpaired electrons and the 13C atoms in the case of graphitized zeolites while this interaction is not observed in normal zeolites. This is assigned to the presence of charge transfer complexes in the close vicinity of graphite areas and to the possible electron transfer to the graphitized domain. Using cyclic voltammetry, an electrochemical response is observed for the first time in such systems demonstrating the role played by graphite in the electron transfers

Layer-by-Layer modification of graphite felt with MWCNT for vanadium redox flow battery

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Electrochemical analysis of a microbial electrochemical snorkel in laboratory and constructed wetlands

International audienceMicrobial electrochemical snorkel (MES) is a short-circuited microbial fuel cell applicable to water treatment that does not produce energy but requires lower cost for its implementation. Few reports have already described its water treatment capabilities but no deeper electrochemical analysis were yet performed. We tested various materials (iron, stainless steel and porous graphite) and configurations of snorkel in order to better understand the rules that will control in a wetland the mixed potential of this self-powered system. We designed a model snorkel that was studied in laboratory and on the field. We confirmed the development of MES by identifying anodic and cathodic parts, by measuring the current between them and by analyzing microbial ecology in laboratory and field experiments. An important application is denitrification of surface water. Here we discuss the influence of nitrate on its electrochemical response and denitrification performances. Introducing nitrate caused the increase of the mixed potential of MES and of current at a potential value relatively more positive than for nitrate-reducing biocathodes described in the literature. The major criteria for promoting application of MES in artificial wetland dedicated to mitigation of non-point source nitrate pollution from agricultural water are considered