Determination of the selenium (VI)/(IV) standard redox potential by cyclic voltammetry

Partially selenized FeCo layered double hydroxide as bifunctional electrocatalyst for efficient and stable alkaline (sea)water splitting

Seawater electrolysis to produce hydrogen is a clean and sustainable strategy for the development of clean and sustainable energy storage systems. However, the erosion and destruction of electrocatalysts of the devices by Cl- in seawater during splitting process make it very difficult to realize. In this work, a partially selenized FeCo layered double hydroxide (Se-FeCo-LDH) catalyst is successfully synthesized, which shows good electrocatalytic performance in seawater during water splitting due to both its excellent conductivity and large surface area. Moreover, an anion aggregation layer around the electrode during the catalytic process can be formed to avoid electrode erosion and destruction by Cl- as well as the competitive reaction of chloride oxidation with the oxygen evolution reaction (OER), which not only improves the catalytic efficiency but also the durability of the catalyst. As a result, the overpotential is only 229 mV at a current density of 100 mA cm-2 for OER in 1 M KOH. Only 1.446 V and 1.491 V voltages are required to reach a current density of 10 mA cm-2 in overall alkaline water and seawater splitting, respectively. Besides, this Se-FeCo-LDH catalyst also achieves long-term stability up to 245 h in overall alkaline seawater splitting. The development of Se-FeCo-LDH catalyst should have an enlightening effect in the field of hydrogen production by (sea)water electrolysis.

Mechanistic Insight into the Abiotic Interactions of Selenate and Selenite with Natural Organic Matter

Natural organic matter (NOM) decreases the selenium (Se) mobility in soil and sediment. Biotic dissimilatory reduction of selenate and selenite and assimilation of the reduced Se species into biomolecules are thought to be primarily responsible for this decreased Se mobility. However, the possibility of Se immobilization due to the abiotic interaction of Se species with NOM is still poorly understood. Equilibrating selenate and selenite with a model NOM (Pahokee peat soil), followed by X-ray absorption spectroscopic analysis, this study shows that the NOM can abiotically reduce highly mobile selenate into relatively less mobile selenite. NOM can sorb Se species, especially selenite, considerably. Preloading of the NOM with Fe(III) increases the sorption of selenite and selenate by several orders of magnitude. Modeling of the Se and Fe K-edge EXAFS data revealed that Se species are sorbed to NOM due to indirect complexation with the organically complexed Fe(O,OH)6 octahedra through the corner- (2C) and edge-sharing (1E) and direct complexation with the oxygen-containing functional groups of the NOM. This study concludes that the abiotic reduction and complexation of the Se species with NOM can be the additional or alternative route of Se immobilization in the NOM-rich soil and sediment.

Performance Evaluation of Selenite (SeO32−) Reduction by Enterococcus spp

Lactic acid bacteria (LAB) such as Enterococcus spp. have an advantage over several bacteria because of their ability to easily adapt to extreme conditions which include high temperatures, highly acidic or alkaline conditions and toxic metals. Although many microorganisms have been shown to reduce selenite (SeO32−) to elemental selenium (Se0), not much work has been done on the combined effect of Enterococcus spp. In this study, aerobic batch reduction of different selenite concentrations (1, 3 and 5 mM) was conducted using Enterococcus hermanniensis sp. and Enterococcus gallinarum sp. (3.5 h, 35 ± 2 °C, starting pH > 8.5). Results from the experiments showed that the average reductions rates were 0.608, 1.921 and 3.238 mmol·(L·h)−1, for the 1, 3 and 5 mM SeO32− concentrations respectively. In addition, more selenite was reduced for the 5 mM concentration compared to the 1 and 3 mM concentrations albeit constant biomass being used for all experiments. Other parameters which were monitored were the glucose consumption rate, protein variation, pH and ORP (oxidation reduction potential). TEM analysis was also conducted and it showed the location of electron-dense selenium nanoparticles (SeNPs). From the results obtained in this study, the authors concluded that Enterococcus species’s high adaptability makes it suitable for rapid selenium reduction and biosynthesis of elemental selenium.

Tubular polyoxoanion [(SeMo6O21)2(C2O4)3]10− and its transformations

Tubular [(SeMo₆O₂₁)₂(C₂O₄)₃]¹⁰⁻ polyoxoanion can be assembled from Na₂MoO₄/SeO₂/H₂C₂O₄ system. TBABr precipitates complexes of [Mo₆O₁₉]²⁻ and [β-Mo₈O₂₆Na₂(NO₃)]³⁻ from its aqueous solution. Speciation of [β-Mo₈O₂₆]⁴⁻ and [Mo₆O₁₉]²⁻ has been studied.

Computational electrochemistry of a novel ferrocene derivative

In this study, the structural and redox properties of a novel ferrocene derivative in dichlomethane solvent were investigated. For this aim, various exchange-correlation functionals and basis sets in gas phase with different continuum solvation models and cavities in liquid phase were applied. The results indicated that UM06/6-31++G(d,p)/SDD level of theory successfully calculated bond lengths and angles with MADs = 0.02 Å and 0.78 deg., respectively. Also, its combination with CPCM-Pauling-UHF/6-31+G(d)/SDD level of theory in liquid phase effectively computed the redox potential with 0.06 V deviation from the experimental value. Moreover, transferability of the proposed method was studied through ferrocene molecule and its new synthesized derivative.