Solvent molecules form surface redox mediators in situ and cocatalyze O2 reduction on Pd

Solvent molecules influence the reactions of molecular hydrogen and oxygen on palladium nanoparticles. Organic solvents activate to form reactive surface intermediates that mediate oxygen reduction through pathways distinct from reactions in pure water. Kinetic measurements and ab initio quantum chemical calculations indicate that methanol and water cocatalyze oxygen reduction by facilitating proton-electron transfer reactions. Methanol generates hydroxymethyl intermediates on palladium surfaces that efficiently transfer protons and electrons to oxygen to form hydrogen peroxide and formaldehyde. Formaldehyde subsequently oxidizes hydrogen to regenerate hydroxymethyl. Water, on the other hand, heterolytically oxidizes hydrogen to produce hydronium ions and electrons that reduce oxygen. These findings suggest that reactions of solvent molecules at solid-liquid interfaces can generate redox mediators in situ and provide opportunities to substantially increase rates and selectivities for catalytic reactions.

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Synergistic oxygen reduction of dual redox catalysts boosting the power of lithium–air battery

Physical Chemistry Chemical Physics ◽

10.1039/c8cp04744h ◽

2018 ◽

Vol 20 (44) ◽

pp. 27930-27936 ◽

Cited By ~ 7

Author(s):

Yun Guang Zhu ◽

F. W. Thomas Goh ◽

Ruiting Yan ◽

Sisi Wu ◽

Stefan Adams ◽

...

Keyword(s):

Oxygen Reduction Reaction ◽

Oxygen Reduction ◽

Power Density ◽

Reduction Reaction ◽

Redox Mediators ◽

Dry Air ◽

Redox Catalysts ◽

Air Battery

The mechanism of redox-mediated oxygen reduction reaction is unequivocally revealed by in situ spectroelectrochemical studies. With judiciously selected redox mediators, the cell operates at near unity utilization of Li metal and presents an unprecedented power density in O2 and dry air.

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A Revised O2 Reduction Model in Li-O2 Batteries as Revealed by in Situ Small Angle X-Ray Scattering

10.26434/chemrxiv.11447775.v1 ◽

2019 ◽

Author(s):

Christian Prehal ◽

Aleksej Samojlov ◽

Manfred Nachtnebel ◽

Manfred Kriechbaum ◽

Heinz Amenitsch ◽

...

Keyword(s):

Small Angle ◽

Wide Angle ◽

Reduction Mechanism ◽

Reduction Model ◽

X Ray ◽

X Ray Scattering ◽

O2 Reduction ◽

Ray Scattering

<b>Here we use in situ small and wide angle X-ray scattering to elucidate unexpected mechanistic insights of the O2 reduction mechanism in Li-O2 batteries.<br></b>

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The role of (bio)surfactant sorption in promoting the bioavailability of nutrients localized at the solid-water interface

Water Science & Technology ◽

10.2166/wst.1999.0336 ◽

1999 ◽

Vol 39 (7) ◽

pp. 91-98 ◽

Cited By ~ 3

Author(s):

Ryan N. Jordan ◽

Eric P. Nichols ◽

Alfred B. Cunningham

Keyword(s):

Mass Transfer ◽

Cell Membrane ◽

Substrate Concentration ◽

Water Interface ◽

Industrial Systems ◽

Solid Liquid Interface ◽

Solid Liquid ◽

Surfactant Sorption

Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailability of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.

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Wetting of glass surface using natural surfactants

Micro and Nanosystems ◽

10.2174/1876402912666200219111447 ◽

2020 ◽

Vol 12 ◽

Author(s):

Nihar Ranjan Biswal

Keyword(s):

Contact Angle ◽

Glass Surface ◽

Pure Water ◽

Amyl Alcohol ◽

Synthetic Surfactant ◽

Wide Range ◽

Different Types ◽

Natural Surfactants ◽

Triton X ◽

Solid Liquid

Background: Surfactant adsorption at the interfaces (solid–liquid, liquid–air, or liquid–liquid) is receiving considerable attention from a long time due to its wide range of practical applications. Objective: Specifically wettability of solid surface by liquids is mainly measured by contact angle and has many practical importances where solid–liquid systems are used. Adsorption of surfactants plays an important role in the wetting process. The wetting behaviours of three plant-based natural surfactants (Reetha, Shikakai, and Acacia) on the glass surface are compared with one widely used nonionic synthetic surfactant (Triton X-100) and reported in this study. Methods: The dynamic contact angle study of three different types of plant surfactants (Reetha, Shikakai and Acacia) and one synthetic surfactant (Triton X 100) on the glass surface has been carried out. The effect of two different types of alcohols such as Methanol and amyl alcohol on wettability of shikakai, as it shows little higher value of contact angle on glass surface has been measured. Results: The contact angle measurements show that there is an increase in contact angle from 47° (pure water) to 67.72°, 65.57°, 68.84°, and 68.79° for Reetha, Acacia, Shikakai, and Triton X-100 respectively with the increase in surfactant concentration and remain constant at CMC. The change in contact angle of Shikakai-Amyl alcohol mixtures are slightly different than that of methanol-Shikakai mixture, mostly there is a gradual increase in contact angle with the increasing in alcohol concentration. Conclusion: There is no linear relationship between cos θ and inverse of surface tension. There was a linear increase in surface free energy results with increase in concentration as more surfactant molecules were adsorbing at the interface enhancing an increase in contact angle.

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