Sharp kinetic acceleration potentials during mediated redox catalysis of insulators

Abstract Redox mediators could catalyse otherwise slow and energy-inefficient cycling of Li-S and Li-O2 batteries by shuttling electrons/holes between the electrode and the solid insulating storage materials. For mediators to work efficiently they need to oxidize the solid with fast kinetics yet the lowest possible overpotential. Here, we found that when the redox potentials of mediators are tuned via, e.g., Li+ concentration in the electrolyte, they exhibit distinct threshold potentials, where the kinetics accelerate several-fold within a range as small as 10 mV. This phenomenon is independent of types of mediators and electrolyte. The acceleration originates from the overpotentials required to activate fast Li+/e– extraction and the following chemical step at specific abundant surface facets. Efficient redox catalysis at insulating solids requires therefore carefully considering the surface conditions of the storage materials and electrolyte-dependent redox potentials, which may be tuned by salt concentrations or solvents.

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Laccases: Versatile Biocatalysts for the Synthesis of Heterocyclic Cores

Molecules ◽

10.3390/molecules26123719 ◽

2021 ◽

Vol 26 (12) ◽

pp. 3719

Author(s):

Ana Catarina Sousa ◽

Lígia O. Martins ◽

M. Paula Robalo

Keyword(s):

Membered Ring ◽

Low Molecular Weight ◽

Redox Potentials ◽

Redox Mediators ◽

Multicopper Oxidases ◽

Phenothiazine Derivatives ◽

Ph Values ◽

Electron Shuttles ◽

Specific Oxidation ◽

Optimal Ph

Laccases are multicopper oxidases that have shown a great potential in various biotechnological and green chemistry processes mainly due to their high relative non-specific oxidation of phenols, arylamines and some inorganic metals, and their high redox potentials that can span from 500 to 800 mV vs. SHE. Other advantages of laccases include the use of readily available oxygen as a second substrate, the formation of water as a side-product and no requirement for cofactors. Importantly, addition of low-molecular-weight redox mediators that act as electron shuttles, promoting the oxidation of complex bulky substrates and/or of higher redox potential than the enzymes themselves, can further expand their substrate scope, in the so-called laccase-mediated systems (LMS). Laccase bioprocesses can be designed for efficiency at both acidic and basic conditions since it is known that fungal and bacterial laccases exhibit distinct optimal pH values for the similar phenolic and aromatic amines. This review covers studies on the synthesis of five- and six-membered ring heterocyclic cores, such as benzimidazoles, benzofurans, benzothiazoles, quinazoline and quinazolinone, phenazine, phenoxazine, phenoxazinone and phenothiazine derivatives. The enzymes used and the reaction protocols are briefly outlined, and the mechanistic pathways described.

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Electrolyte Composition in Li/O2 Batteries with LiI Redox Mediators: Solvation Effects on Redox Potentials and Implications for Redox Shuttling

The Journal of Physical Chemistry C ◽

10.1021/acs.jpcc.7b11859 ◽

2018 ◽

Vol 122 (3) ◽

pp. 1522-1534 ◽

Cited By ~ 21

Author(s):

Azusa Nakanishi ◽

Morgan L. Thomas ◽

Hoi-Min Kwon ◽

Yuki Kobayashi ◽

Ryoichi Tatara ◽

...

Keyword(s):

Electrolyte Composition ◽

Redox Potentials ◽

Redox Mediators ◽

Solvation Effects

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The stimulation of photophosphorylation and ATPase by artificial redox mediators in chromatophores ofRhodopseudomonas capsulata at different redox potentials

Journal of Bioenergetics and Biomembranes ◽

10.1007/bf00743157 ◽

1979 ◽

Vol 11 (1-2) ◽

pp. 1-16 ◽

Cited By ~ 14

Author(s):

Assunta Baccarini-Melandri ◽

B. Andrea Melandri ◽

G�nter Hauska

Keyword(s):

Redox Potentials ◽

Redox Mediators ◽

Stimulation Of

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Catalytic effects of different redox mediators on the reductive decolorization of azo dyes

Water Science & Technology ◽

10.2166/wst.2006.500 ◽

2006 ◽

Vol 54 (2) ◽

pp. 165-170 ◽

Cited By ~ 15

Author(s):

A.A. Encinas-Yocupicio ◽

E. Razo-Flores ◽

F. Sánchez-Díaz ◽

A.B. dos Santos ◽

J.A. Field ◽

...

Keyword(s):

Azo Dyes ◽

Granular Sludge ◽

Order Rate Constant ◽

Anaerobic Treatment ◽

Redox Mediator ◽

Redox Potentials ◽

Redox Mediators ◽

Direct Blue ◽

Reactive Orange ◽

Catalytic Effects

The catalytic effects of redox mediators, with distinct standard redox potentials (E′0), were evaluated on the first-order rate constant of decolorization (Kd) of recalcitrant azo dyes by an anaerobic granular sludge. The dyes studied included mono-azo (Reactive Orange 14, RO14), di-azo (Direct Blue 53, DB53), and tri-azo (Direct Blue 71, DB71) compounds. Toxicity and auto-catalytic aspects seemed to play a role in determining the rate of decolorization. Addition of riboflavin, anthraquinone-2,6-disulphonate (AQDS) or lawsone as a redox mediator, increased the Kd value for all dyes studied, although their impact varied in every case. Kd values were increased from 1.1-fold up to 3.8-fold depending on the redox mediator applied. Moreover, catalysts with moderately similar E′0 value caused distinct stimulation on the rate of decolorization. These results should be considered for selecting the proper redox mediator to be applied during the anaerobic treatment of textile wastewaters and effluents containing electron-withdrawing pollutants, such as nitro-aromatic and polychlorinated compounds.

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Investigation of cobalt redox mediators and effects of TiO2 film topology in dye-sensitized solar cells

RSC Advances ◽

10.1039/c6ra07107d ◽

2016 ◽

Vol 6 (61) ◽

pp. 56580-56588 ◽

Cited By ~ 12

Author(s):

Majid Safdari ◽

Peter W. Lohse ◽

Leif Häggman ◽

Sara Frykstrand ◽

Daniel Högberg ◽

...

Keyword(s):

Solar Cells ◽

Light Absorption ◽

Dye Sensitized Solar Cells ◽

Cobalt Complexes ◽

Redox Potentials ◽

Redox Mediators ◽

Visible Light Absorption ◽

Dye Sensitized ◽

Sensitized Solar Cells ◽

Interesting Alternative

Cobalt complexes represent interesting alternative redox mediators in dye-sensitized solar cells, with weak visible light absorption and a wide variety in redox potentials. Its diffusion in mesoporous TiO2 may, however, limit its performance.

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Tripuhyite and schafarzikite: two of the ultimate sinks for antimony in the natural environment

Mineralogical Magazine ◽

10.1180/minmag.2012.076.4.06 ◽

2012 ◽

Vol 76 (4) ◽

pp. 891-902 ◽

Cited By ~ 42

Author(s):

P. Leverett ◽

J. K. Reynolds ◽

A. J. Roper ◽

P. A. Williams

Keyword(s):

Redox Potentials ◽

Near Surface ◽

Surface Conditions ◽

Secondary Minerals ◽

Ambient Temperatures ◽

Supergene Zone ◽

Acidic Conditions ◽

The Common ◽

The Stability ◽

Derived Data

AbstractStudies of the stability of the oxides schafarzikite, FeSb2O4, and tripuhyite, FeSbO4, have been undertaken to clarify the roles these secondary minerals may have in determining the dispersion of antimony in oxidizing environments. Solubilities were determined at 298.15 K in aqueous HNO3, and these data were used to calculate values of ΔGfϴ at the same temperature. The derived Δ Gfϴ (s, 298.15 K) values for FeSb2O4 and FeSbO4 are – 959.4±4.3 and – 836.8±2.2 kJ mol–1, respectively. These results have been compared with electrochemically derived data, extrapolated from 771–981 K. The present study shows conclusively that although the mobility of Sb above the water table is limited by simple Sb(III) and Sb(V) oxides and stibiconite-group minerals, depending upon the prevailing redox potential and pH, tripuhyite is an important ultimate sink for Sb in the supergene environment. It is highly insoluble even in strongly acidic conditions and its anomalous stability at ambient temperatures causes the common mineral goethite, FeOOH, to react to form tripuhyite at activities of Sb(OH)5(aq) as low as 10–11. The comparatively limited numbers of reported occurrences of tripuhyite in the supergene zone are almost certainly due to the fact that its physical properties, especially colour and habit, are remarkably similar to those of goethite. In contrast, the small number of reported occurrences of schafarzikite can be related to its decomposition to tripuhyite as redox potentials rise at the top of the supergene zone and the fact that it decomposes to sénarmontite, Sb2O3, in acidic conditions, releasing Fe2+ ions into solution. In general, the findings confirm the immobility of Sb in near-surface conditions. Geochemical settings favouring the formation of the above minerals have been assessed using the results of the present study and data from the literature.

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The oxidation of Inconel alloy MA754 at low oxidation potential

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100074884 ◽

1983 ◽

Vol 41 ◽

pp. 218-219

Author(s):

D. N. Braski ◽

P. D. Goodell ◽

J. V. Cathcart ◽

R. H. Kane

Keyword(s):

Surface Layer ◽

Oxidation Potential ◽

Metal Interface ◽

Elevated Temperature Strength ◽

Surface Conditions ◽

Inconel Alloy ◽

Inco Alloy ◽

Resistance To Oxidation ◽

Oxide Particles ◽

Cold Worked

It has been known for some time that the addition of small oxide particles to an 80 Ni—20 Cr alloy not only increases its elevated-temperature strength, but also markedly improves its resistance to oxidation. The mechanism by which the oxide dispersoid enhances the oxidation resistance is being studied collaboratively by ORNL and INCO Alloy Products Company.Initial experiments were performed using INCONEL alloy MA754, which is nominally: 78 Ni, 20 Cr, 0.05 C, 0.3 Al, 0.5 Ti, 1.0 Fe, and 0.6 Y2O3 (wt %).Small disks (3 mm diam × 0.38 mm thick) were cut from MA754 plate stock and prepared with two different surface conditions. The first was prepared by mechanically polishing one side of a disk through 0.5 μm diamond on a syntron polisher while the second used an additional sulfuric acid-methanol electropolishing treatment to remove the cold-worked surface layer. Disks having both surface treatments were oxidized in a radiantly heated furnace for 30 s at 1000°C. Three different environments were investigated: hydrogen with nominal dew points of 0°C, —25°C, and —55°C. The oxide particles and films were examined in TEM by using extraction replicas (carbon) and by backpolishing to the oxide/metal interface. The particles were analyzed by EDS and SAD.

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