Selectivity and competition between the anodic evolution of oxygen and chlorine

Sustainable energy from wind and solar is most readily available near the sea. Seawater electrolysis would thus be a highly promising method for intermittently storing surplus electricity from these sources, in the form of hydrogen. Unfortunately, the direct use of seawater in electrolysers brings with it a selectivity problem, caused by the chloride salts in such water. Instead of forming oxygen at the anode, which is environmentally harmless and thus the desired product, the formation of toxic chlorine becomes possible in seawater, and this reaction has to be avoided. This thesis is focussed on how the anodic evolution of oxygen and chlorine compete, and how selectivity between these two reactions may be optimized for the benefit of seawater electrolysis, and electrocatalysis in general.NWO; Nouryon; Shell Global Solutions; Magneto Special Anodes (an Evoqua Brand); Elson TechnologiesCatalysis and Surface Chemistr

All-optical octave-broad ultrafast switching of Si woodpile photonic band gap crystals

We present ultrafast all-optical switching measurements of Si woodpile photonic band gap crystals. The crystals are spatially homogeneously excited and probed by measuring reflectivity over an octave in frequency (including the telecommunication range) as a function of time. After 300 fs, the complete stop band has shifted to higher frequencies as a result of optically excited free carriers. The switched state relaxes quickly with a time constant of 18 ps. We present a quantitative analysis of switched spectra with theory for finite photonic crystals. The induced changes in refractive index are well described by a Drude model with a carrier relaxation time of 10 fs. We briefly discuss possible applications of high-repetition-rate switching of photonic crystal cavities

Examination and Prevention of Ring Collection Failure During Gas-Evolving Reactions on a Rotating Ring-Disk Electrode

Use of a rotating ring-disk electrode during gas-evolving reactions has been shown liable to errors under higher current densities, since product collection on the ring is vulnerable to the formation of gas bubbles at the disk-ring interspace. In this study, we explored methods of reducing such bubble-related errors and improving the reliability of the collection factor under high-intensity gas evolution. We attempted the mounting of a thin wire close to the surface, to dislodge bubbles that formed specifically on the interface between the disk and the disk-ring spacer. This approach was tested for the detection of chlorine during parallel chlorine and oxygen evolution, and resulted in a notable alteration of the collection efficiency; its value became lower than theoretical expectations and also quite stable, even under higher current densities. We also coated the RRDE tip in a hydrophilic polymer, to reduce the tendency of bubble formation; this was tested for the collection of hydrogen and oxygen gas, and led to a mild increase in overall performance. The coating allowed for approximately 50% higher hydrogen evolution current density without ring failure, and for oxygen collection led to an overall improvement in behaviour.Catalysis and Surface Chemistr

Measurement of competition between oxygen evolution and chlorine evolution using rotating ring-disk electrode voltammetry

Catalysis and Surface Chemistr

Novel Polypyridyl Ruthenium(II) Complexes Containing Oxalamidines as Ligands.

The complexes [Ru(bpy)2(H2TPOA)](PF6)2 ⋅ 4H2O, (1); [Ru(Me-bpy)2(H2TPOA)](PF6)2 ⋅ 2H2O, (2); [Ru(bpy)2(H2TTOA)](PF6)2 ⋅ 2H2O, (3); [Ru(Me-bpy)2(H2TTOA)](PF6)2 ⋅ 2H2O, (4) and {[Ru(bpy)2]2(TPOA)}(PF6)2 ⋅ 2H2O, (5) (where bpy is 2,2´bipyridine; Me-bpy is 4,4´- dimethyl-2,2´-bipyridine; H2TPOA is N, N´, N´´, N´´´- tetraphenyloxalamidine; H2TTOA is N, N´, N´´, N´´´- tetratolyloxalamidine) have been synthesized and characterized by 1H-NMR, FAB-MS, infrared spectroscopy and elemental analysis. The X-ray investigation shows the coordination of the still protonated oxalamidine moiety via the 1,2−diimine unit. The dimeric compound (5) could be separated in its diastereoisomers (5´) and (5´´) by repeated recrystallisation. The diastereomeric forms exhibit different 1H-NMR spectra and slightly shifted electronic spectra. Compared with the model compound [Ru(bpy)3]2+, the absorption maxima of (1)–(5) are shifted to lower energies. The mononuclear complexes show Ru(III/II)- couples at about 0.9 V vs SCE, while for the dinuclear complex two well defined metal based redox couples are observed at 0.45 and 0.65 V indicating substantial interaction between the two metal centres

Athymic nude rat. III natural cell mediated cytotoxicity.

Homozygous rnu/rnu and heterozygous +/rnu rats were investigated and compared with each other for the existence of natural cell-mediated cytotoxicity. Investigated were total, adherent, and nonadherent cell populations from spleen, peritoneal cavity, and mesenteric lymph node. The natural killer (NK) cell activity was measured in a 4-hr 51Cr-release assay with a xenogeneic murine YAC lymphoma target cell line. In both and +/rnu rats the peritoneal cavity had the highest percentage of activity, while the spleen and mesenteric lymph node showed a lower activity. The mesenteric lymph node of +/rnu rats of 8–10 weeks of age was found to express a very low activity, in contrast to a very high activity in rats. For almost every effector to target cell (E:T) ratio investigated (100, 70, 50, and 10), the natural killer cell activity in the nude rats was found to be significantly higher than in their thymus-bearing littermates. In comparison with that of +/rnu rats, NK activity in the nonadherent cell fractions of athymic rats was 50 to 60% higher in spleen cells, doubled in peritoneal cells, and increased 10-fold or higher in lymph node cells. Investigations o

Competition and selectivity during parallel evolution of bromine, chlorine and oxygen on IrOx electrodes

During hydrogen production for (renewable) energy storage, direct seawater electrolysis offers several notable advantages over freshwater electrolysis. Unfortunately, it is also hindered by possible oxidation reactions of chloride and (to a lesser extent) bromide, which can occur in parallel to the evolution of oxygen and form harmful by-products at the anode. Although the respective oxidation reactions of Br- and Cl- have been researched quite well on Pt, not much is known concerning bromide oxidation and its effect on the evolution of chlorine and oxygen for metal oxides, which are the class of electrocatalysts overwhelmingly used in industry. Using glassy carbon-supported iridium oxide (IrOx) as a model system, we investigated the oxidation behaviour of this well-known oxygen evolution catalyst in an acidic Br-/Cl- electrolyte. We first briefly discuss the solution chemistry and oxidation products that may be expected. Model studies were performed of the parallel evolution of Br-2, Cl-2 and O-2 to increase the understanding of the anodic competition problem, with a special focus on the selectivity towards oxygen. Using rotating ring-disk voltammetry and UV-Vis spectroscopy, our results suggest that bromide and chloride competitively absorb on IrOx, but do not alter each other's oxidation reaction mechanisms, which both seem to adhere best to a Volmer-Heyrovsky mechanism. We also find that bromide and chloride adsorption significantly slow down the oxygen evolution reaction, in an additive way. Even a relatively small amount of bromide highly affected the oxygen evolution selectivity. Formation of the interhalogen compound BrCl, which is possible in a mixed Br-/Cl- electrolyte, does not seem to occur. (C) 2020 The Authors. Published by Elsevier Inc.Catalysis and Surface Chemistr

Contaminant-induced immunotoxicity in harbour seals: Wildlife at risk?

Persistent, lipophilic polyhalogenated aromatic hydrocarbons (PHAHs) accumulate readily in the aquatic food chain and are found in high concentrations in seals and other marine mammals. Recent mass mortalities among several marine mammal populations have been attributed to infection by morbilliviruses, but a contributing role for immunotoxic PHAHs, including the polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) was not ruled out. We addressed this issue by carrying out a semi-field study in which captive harbour seals were fed herring from either the relatively uncontaminated Atlantic Ocean or the contaminated Baltic Sea for 2 years. We present here an overview of results obtained during this study. An impairment of natural killer (NK) cell activity, in vitro T-lymphocyte function, antigen-specific in vitro lymphocyte proliferative responses, and in vivo delayed-type hypersensitivity and antibody responses to ovalbumin was observed in the seals fed the contaminated Baltic herring. Additional feeding studies in PVG rats using the same herring batches suggested that an effect at the level of the thymus may be responsible for changes in cellular immunity, that virus-specific immune responses may be impaired, and that perinatal exposure to environmental contaminants represents a greater immunotoxic threat than exposure as a juvenile or adult. Together with the pattern of TCDD toxic equivalents of different PHAHs in the herring, these data indicate that present levels of PCBs in the aquatic food chain a