scholarly journals Electrochemical, Spectroscopic, and Computational Investigations on Redox Reactions of Selenium Species on Galena Surfaces

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 437 ◽  
Author(s):  
Peter Cook ◽  
YoungJae Kim ◽  
Ke Yuan ◽  
Maria C. Marcano ◽  
Udo Becker
Keyword(s):  
Photoelectron Spectroscopy ◽  
Redox Reactions ◽  
Redox Potentials ◽  
Free Energies ◽  
Cathodic Peak ◽  
Redox Transformation ◽  
Hydrogen Electrode ◽  
Midpoint Potential ◽  
Ph Conditions ◽  
Cv Measurements

Despite previous studies investigating selenium (Se) redox reactions in the presence of semiconducting minerals, Se redox reactions mediated by galena (PbS) are poorly understood. In this study, the redox chemistry of Se on galena is investigated over a range of environmentally relevant Eh and pH conditions (+0.3 to −0.6 V vs. standard hydrogen electrode, SHE; pH 4.6) using a combination of electrochemical, spectroscopic, and computational approaches. Cyclic voltammetry (CV) measurements reveal one anodic/cathodic peak pair at a midpoint potential of +30 mV (vs. SHE) that represents reduction and oxidation between HSeO3− and H2Se/HSe−. Two peak pairs with midpoint potentials of −400 and −520 mV represent the redox transformation from Se(0) to HSe− and H2Se species, respectively. The changes in Gibbs free energies of adsorption of Se species on galena surfaces as a function of Se oxidation state were modeled using quantum-mechanical calculations and the resulting electrochemical peak shifts are (−0.17 eV for HSeO3−/H2Se, −0.07 eV for HSeO3−/HSe−, 0.15 eV for Se(0)/HSe−, and −0.15 eV for Se(0)/H2Se). These shifts explain deviation between Nernstian equilibrium redox potentials and observed midpoint potentials. X-ray photoelectron spectroscopy (XPS) analysis reveals the formation of Se(0) potentials below −100 mV and Se(0) and Se(−II) species at potentials below −400 mV.

scholarly journals A Computational Protocol Combining DFT and Cheminformatics for Prediction of pH-Dependent Redox Potentials

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3978
Author(s):  
Rocco Peter Fornari ◽  
Piotr de Silva
Keyword(s):  
Organic Molecules ◽  
Ph Value ◽  
Computational Cost ◽  
Legendre Transform ◽  
Good Prediction ◽  
Redox Potentials ◽  
Free Energies ◽  
Hybrid Functional ◽  
Data Set ◽  
State Changes

Discovering new materials for energy storage requires reliable and efficient protocols for predicting key properties of unknown compounds. In the context of the search for new organic electrolytes for redox flow batteries, we present and validate a robust procedure to calculate the redox potentials of organic molecules at any pH value, using widely available quantum chemistry and cheminformatics methods. Using a consistent experimental data set for validation, we explore and compare a few different methods for calculating reaction free energies, the treatment of solvation, and the effect of pH on redox potentials. We find that the B3LYP hybrid functional with the COSMO solvation method, in conjunction with thermal contributions evaluated from BLYP gas-phase harmonic frequencies, yields a good prediction of pH = 0 redox potentials at a moderate computational cost. To predict how the potentials are affected by pH, we propose an improved version of the Alberty-Legendre transform that allows the construction of a more realistic Pourbaix diagram by taking into account how the protonation state changes with pH.

scholarly journals Mixed H2O/H2 Plasma-Induced Redox Reactions of Thin Uranium Oxide Films under UHV Conditions

2021 ◽  
Author(s):  
Ghada El Jamal ◽  
Thomas Gouder ◽  
Rachel Eloirdi ◽  
Evgenia Tereshina-Chitrova ◽  
Lukáš Horák ◽  
...  
Keyword(s):  
Thin Films ◽  
Photoelectron Spectroscopy ◽  
Redox Reactions ◽  
Uranium Oxide ◽  
Oxide Films ◽  
X Ray ◽  
Gas Plasma

X-Ray Photoelectron Spectroscopy (XPS) has been used to study the effect of mixed H2O/H2 gas plasma on the surface of UO2, U2O5 and UO3 thin films at 400 °C. The...

Interaction of nitric oxide with Ru(II) complexes of deuteroporphyrindimethylester derivatives

2009 ◽  
Vol 13 (01) ◽  
pp. 35-40 ◽  
Author(s):  
Rudy Martin ◽  
Roberto Cao ◽  
Ana M. Esteva ◽  
Franz-Peter Montforts
Keyword(s):  
Nitric Oxide ◽  
Photoelectron Spectroscopy ◽  
Gold Electrode ◽  
Charge Transfer Band ◽  
Bathochromic Shift ◽  
Considerable Change ◽  
Cathodic Peak ◽  
X Ray ◽  
Polycrystalline Gold ◽  
Self Assembled

A new ruthenium(II) porphyrin disulphide derivative, [ Ru ( Pds )( CO )], was obtained from ruthenium(II)(carbonyl)deuteroporphyrin(IX), [ Ru ( DPdc )( CO )] and cystamine. The interaction of this complex with nitric oxide was studied spectrophotometrically and a bathochromic shift of the charge transfer band and considerable change in the α and β bands of the complex were observed. According to the IR spectrum, the product of this interaction is [ Ru ( DmDP )( NO +)( NO 2-)]. [ Ru ( Pds )( CO )] was then self-assembled on polycrystalline gold and characterized by X-ray photoelectron spectroscopy. [ Ru ( Pds )( CO )] was also self-assembled on gold electrode beads and its interaction with nitric oxide in aqueous solution was studied by cyclic voltammetry. A shift in the ruthenium redox process and a new irreversible cathodic peak at -0.59 V were observed, both indicating coordination of NO .

scholarly journals Introduction of Bifunctional Group onto MWNT by Radiation-Induced Graft Polymerization and Its Use as Biosensor-Supporting Materials

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Yu-Jin Lee ◽  
Da-Jung Chung ◽  
Sang-Hyub Oh ◽  
Seong-Ho Choi
Keyword(s):  
Photoelectron Spectroscopy ◽  
Glycidyl Methacrylate ◽  
Redox Reactions ◽  
Graft Polymerization ◽  
Red Wine ◽  
Multiwalled Carbon ◽  
X Ray ◽  
Transmission Electron ◽  
Radiation Induced ◽  
Supporting Materials

A biosensor comprisingtyrosinaseimmobilized on bifunctionalized multiwalled carbon nanotube (MWNT) supports was prepared for the detection of phenolic compounds in drinks such as red wine and juices. The MWNT supports were prepared by radiation-induced graft polymerization (RIGP) of epoxy-containing glycidyl methacrylate (GMA), to covalently immobilize thetyrosinase, and vinyl ferrocene (VF), which can act as an electron transfer mediator via redox reactions. The bifunctionalized MWNTs were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). Electrodes prepared with the MWNTs showed increased current with increasing VF content. A biosensor comprisingtyrosinaseimmobilized on the bifunctionalized MWNTs could detect phenol at 0.1–20 mM. Phenolics in red wine and juices were determined using the biosensor after its calibration.

scholarly journals Photochromic coenzyme Q derivatives: switching redox potentials with light

2017 ◽  
Vol 8 (9) ◽  
pp. 6474-6483 ◽  
Author(s):  
Nadja A. Simeth ◽  
Andrea C. Kneuttinger ◽  
Reinhard Sterner ◽  
Burkhard König
Keyword(s):  
Redox Reactions ◽  
Coenzyme Q ◽  
Redox Potentials ◽  
Isolated Mitochondria

A photochromic coenzyme Q derivative could be activated through irradiation with orange light and initiate redox reactions with Hantzsch ester and on isolated mitochondria.

A Critical Evaluation of the Redox Properties of Uranium, Neptunium and Plutonium Ions in Acidic Aqueous Solutions

1999 ◽  
Vol 71 (9) ◽  
pp. 1771-1807 ◽  
Author(s):  
Sorin Kihara ◽  
Zenko Yoshida ◽  
Hisao Aoyagi ◽  
Kohji Maeda ◽  
Osamu Shirai ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Redox Reactions ◽  
Critical Evaluation ◽  
Redox Properties ◽  
Redox Processes ◽  
Redox Potentials ◽  
Electrode Processes ◽  
Reversible Redox ◽  
Reduction Mechanisms ◽  
Current Potential

Standard redox potentials, E0s, and redox processes of U, Np and Pu ions in acidic aqueous solutions are reviewed and evaluated critically. The E0sof reversible redox processes, MO22+/MO2+ and M4+/M3+ (M: U, Np or Pu) adopted are those proposed mainly by Riglet et al. on the basis of the precise correction of formal potentials, E0's, according to the improved theoretical approach to estimate the activity coefficient. Electrode processes of the U, Np and Pu ions are discussed in terms of current-potential curves, measured so far by polarography, voltammetry or flow coulometry. Special attention is payed to the irreversible MO2+/M4+ reactions. Disproportionation reactions of MO2+ are also discussed. New substances are introduced as intermediates during reductions of MO2+ to M4+ or disproportionations of MO2+.CONTENTSIntroductionStandard redox potentials for uranium, neptunium and plutonium ions in acidic aqueous solutions2.1 Evaluation of E0 from E0' determined by electrochemical measurements2.2 Temperature dependence of E0Redox reactions of uranium, neptunium and plutonium in acidic aqueous solutions investigated by polarography or voltammetry3.1 Uranium3.2 Neptunium3.3 Plutonium3.4 Disproportionation of NpO2+, PuO2+, Np4+ and Pu4+3.5 Reduction of MO2+ and reduction intermediatesRedox reactions of uranium, neptunium and plutonium in acidic aqueous solutions investigated by flow coulometry4.1 Electrode processes of the uranium, neptunium and plutonium ions investigated by flow coulometry at the column electrode at the column electrode4.2 Disproportionation of MO2+ during the electrolysis by flow coulometry4.3 Reduction mechanisms of MO2+ (M = Np or Pu) and reduction intermediates investigated by flow coulometryConclusionsList of abbreviationsAppendixReferences

scholarly journals Synthesis of Phosphorus-Containing Polyanilines by Electrochemical Copolymerization

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1029 ◽  
Author(s):  
Beatriz Martínez-Sánchez ◽  
Andrés Felipe Quintero-Jaime ◽  
Francisco Huerta ◽  
Diego Cazorla-Amorós ◽  
Emilia Morallón
Keyword(s):  
Photoelectron Spectroscopy ◽  
Polymeric Materials ◽  
Electroactive Polymers ◽  
Hydrogen Electrode ◽  
X Ray ◽  
Electrochemical Copolymerization ◽  
Phosphorus Containing ◽  
Redox Transitions ◽  
Acid Stable

In this study, the phosphonation of a polyaniline (PANI) backbone was achieved in an acid medium by electrochemical methods using aminophenylphosphonic (APPA) monomers. This was done through the electrochemical copolymerization of aniline with either 2- or 4-aminophenylphosphonic acid. Stable, electroactive polymers were obtained after the oxidation of the monomers up to 1.35 V (reversible hydrogen electrode, RHE). X-ray photoelectron spectroscopy (XPS) results revealed that the position of the phosphonic group in the aromatic ring of the monomer affected the amount of phosphorus incorporated into the copolymer. In addition, the redox transitions of the copolymers were examined by in situ Fourier-transform infrared (FTIR) spectroscopy, and it was concluded that their electroactive structures were analogous to those of PANI. From the APPA monomers it was possible to synthesize, in a controlled manner, polymeric materials with significant amounts of phosphorus in their structure through copolymerization with PANI.

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