Colloidal catalysis. Transport versus surface control

Spiro, M.; Freund, Paul L.

doi:10.1039/f19837901649

Cited by 38 publications

(22 citation statements)

References 5 publications

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“…Earlier studies have reported that electron-transfer reactions occur via colloidal particles . Under such conditions, the particles are found to pick up a mixed potential which is anodic to the reductant and cathodic to the oxidant . Such potentials depend on the size of the particle and the nucleophile present .…”

Section: Resultsmentioning

confidence: 98%

“…Nanoscale systems are an emerging field of research due to their ability to bridge the gap between the atomic and macroscopic scales. − Any particle whose size falls in the range 1−100 nm can be called a nanoparticle whether it is dispersed in gaseous, liquid, or solid medium. These particles comprise clusters of small numbers of atoms.…”

Section: Introductionmentioning

confidence: 99%

“…Size-dependent reactivity and large surface area of these systems lead to their use as efficient catalysts. Earlier studies have probed the catalytic efficiency of surfactant-stabilized nanoparticles. , Here the redox reaction of MB has been used to probe the catalytic function of the nanoparticles of the coinage metals Cu, Ag, and Au.…”

Section: Introductionmentioning

confidence: 99%

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Organized Media as Redox Catalysts

Pal¹,

De²,

Jana³

et al. 1998

Langmuir

125

115

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Micellar catalysis for a methylene blue (MB)−ascorbate ion (AA-) redox reaction (activation energy 114 kJ mol-1) has been observed to occur because of the binding of the substrates onto the micellar surface by hydrophobic and electrostatic interaction. This increases the encounter probability, leading to a substantially accelerated reaction. The reported study indicates that the most likely substrate solubilization sites in micelles and reverse micelles are the interfacial and Stern regions. Studies on the effect of various salting-in and salting-out agents, an increase in the hydrophobicity of the dye, and the size of the reverse micellar water pool provide no evidence of deeper penetration into the micellar core. In addition, a fascile reversible electron-transfer reaction for the MB−AA- and MB−BH4 - systems has been observed with coinage metal sol particles. Metal sol-induced catalysis occurs due to the availability of a suitable substrate which acts as a mediator for the electron-transfer reaction between MB and the reductant.

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Organized Media as Redox Catalysts

Pal¹,

De²,

Jana³

et al. 1998

Langmuir

125

115

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“…Particles were kept in suspension in a small reservoir by bubbling gas, and the dispersion was pumped through the flow circuit by using a Monostate Ministaltic pump. Typical flow rates were 15 cm s"1 2H20 + 2e ^H2 + 20H" (B) (B) and oxidation by (A) would require a fit of the experimental data to (30) or to the special case (A), (36).…”

Section: Resultsmentioning

confidence: 99%

Electrochemical behavior of dispersions of spherical ultramicroelectrodes

Fleischmann¹,

Ghoroghchian²,

Rolison³

et al. 1986

J. Phys. Chem.

178

159

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It is shown that it is possible to carry out electrochemical reactions in poorly conducting and nonconducting media by means of bipolar electrolyses with dispersions. Polarization equations are predicted for highly simplified models based on the concept of the mixture potential, the surface reactions being assumed to be rate determining. Results for hydrogen evolution/oxidation and oxygen evolution/reduction show that the interpretation of polarization curves at high field strengths will have to take into account the effects of diffusion. The results also show that it should be possible to investigate, monitor, and modify heterogeneous catalyses of reactions in the liquid phase by means of the faradaic currents induced by the electric fields.

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“…This reaction has been studied in considerable detail both theoretically [6][7][8][9][10][11][12] and by using various experimental techniques. [13][14][15][16][17][18][19][20][21][22][23][24] Nevertheless, studying the catalytic process (eq 1) experimentally poses severe problems due to the fact that MV 2+ is reduced at more negative potentials than protons under acidic conditions.…”

Section: Introductionmentioning

confidence: 99%

Studying Heterogeneous Catalysis by the Scanning Electrochemical Microscope (SECM): The Reduction of Protons by Methyl Viologen Catalyzed by a Platinum Surface

1999

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The feedback mode of the scanning electrochemical microscope (SECM) was used for studying a surface-catalyzed electron-transfer reaction. As a model system we examined the reduction of protons by reduced N,N‘-dimethyl-4,4‘-bipyridinum, methyl viologen radical cation, MV+•, catalyzed by a platinum surface. The experimental configuration comprises a biased amalgamated Au ultramicroelectrode (UME) that approaches an unbiased Pt UME substrate of the same radius. MV+• that is electrochemically generated at the amalgamated UME is oxidized at the Pt surface as a result of reducing protons. This novel configuration permits the simultaneous measurement of the catalytic current and the mixed potential (open-circuit potential) attained at the Pt surface. The results are interpreted by an electrochemical model which was previously suggested; however, our approach makes it possible to measure, for the first time, the current−potential relation predicted by the theory. Our results indicate that methyl viologen behaves reversibly under all the experimental conditions, and that the rate constant of hydrogen evolution, that is calculated, is in perfect agreement with previous reports. The significant advantages of our approach are discussed as well as its applicability for studying other electrochemical systems.

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Colloidal catalysis. Transport versus surface control

Abstract: It has been shown that the flux of material diffusing to the surface of a colloidal particle is greater than to a plane surface of the same area and diffusion layer thickness (6). Around a small sphere of radius R the effective Nernst layer thickness deff is given by

Cited by 38 publications

References 5 publications

Organized Media as Redox Catalysts

Organized Media as Redox Catalysts

Electrochemical behavior of dispersions of spherical ultramicroelectrodes

Studying Heterogeneous Catalysis by the Scanning Electrochemical Microscope (SECM): The Reduction of Protons by Methyl Viologen Catalyzed by a Platinum Surface

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