Systematische Untersuchung an Elektrokatalysatoren der Sauerstoffreduktion*

Behret, H.; Clauberg, W.; Sandstede, G.

doi:10.1524/zpch.1978.113.1.097

Cited by 22 publications

(4 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One of the arguments is that the standard potentials of M3+/M2+ couples correlate so well with the electrocatalytic activity of their N4-chelated complexes. 28 In our experiments, however, there is no spectroscopical evidence for interaction between oxygen and the adsorbed FePc layer at potentials where the Fe3+/Fe2+ couple exists.…”

Section: Discussioncontrasting

confidence: 70%

Electrocatalytic oxygen reduction: the role of oxygen bridges as a structural factor in the activity of transition-metal phthalocyanines

Ham¹,

Hinnen²,

Magner³

et al. 1987

J. Phys. Chem.

View full text Add to dashboard Cite

ionic) character peculiar to the S, perp minima. The latter avoided crossing is similar in nature to the 'B-'A (vibronically) avoided crossing involved in the trans -* cis photoisomerism of stilbene.39 The observed decrease of the activation energies with increasing solvent polarity can easily be explained within the proposed mechanism. In fact, because of their high dipole moments (~1 0 D) S, perp minima may be markedly stabilized in highly polar solvents and this may cause appreciable lowering of the trans -* perp barriers.4. The photoreaction mechanism is well interpretable in the light of both the experimental results and theoretical calculations. The nonadiabatic singlet mechanism (activated twisting to the funnel 'perp, internal conversion to °perp, and relaxation to the two geometrical isomers), favored in the case of stilbene because of the small A£tp, is operative here only at high temperatures because of the high barriers. At room temperature or below room temperature (depending on the solvent), where and rF remain constant, the fluorescent state is no longer the isomerizable state and the photoreaction proceeds through a different pathway. According to the calculation results which do not show any evidence for the existence of other singlet states below the fluorescent St state (Figure 5), the most reasonable and least speculative assumption is that the triplet pathway becomes the prevalent mechanism for isomerization. Fluorescence and ISC seem then to offer the predominant deactivation pathways in these experimental conditions. The smaller photoisomerization quantum yields obtained, compared to stilbene, are thus easily understood since kF is here of the same order of magnitude as kISC, the rate for the reactive deactivation at or below room temperature. The comparison of the rate parameters for the competitive deactivation processes of S, clearly indicate the relative weight of the two reaction mechanisms at any temperature.5. The results obtained, different from those of stilbene but similar to those of StNs, indicate that the observed behavior is probably of general character. They show that, when one of the phenyl groups of stilbene is replaced by a polycyclic group (naphthyl, phenanthryl, etc.) of low S, energy, the lowest excited states acquire an increasing aromatic character thus leading to high activation energies for the 'trans -'perp rotation and correspondingly to high values. Consequently, the photoisomerization mechanism gradually change from singlet to triplet and the radiative decay becomes the main deactivation path of excited styrylaromatics.Acknowledgment. Financial support by the Consiglio Nazionale delle Ricerche and Ministero per la Pubblica Istruzione (Roma) and by the Centro di Calcólo Elettronico (University of Modena) is gratefully acknowledged. A.S. thanks the Associazione Italiana per la Ricerca Industríale for the award of a fellowship.

show abstract

Section: Discussioncontrasting

confidence: 70%

Electrocatalytic oxygen reduction: the role of oxygen bridges as a structural factor in the activity of transition-metal phthalocyanines

Ham¹,

Hinnen²,

Magner³

et al. 1987

J. Phys. Chem.

View full text Add to dashboard Cite

show abstract

“…CatQ + e----> (CatO2) [2] (CatQ)-+ 2H + ---> Cat + + H20:~ [3] where, Cat represents a catalytic site and CatO:, di-oxygenoccupied site. The proposed mechanism is similar to the reaction scheme for the electrocatalytic reduction of oxygen on Pt, glassy carbon, and phthalocyanine modified electrodes.…”

Section: That Is O~ + Cat E-> Cato2mentioning

confidence: 99%

“…I'2 However, this method requires the use of a smooth model electrode, the voltage range in which kinetic control prevails is often narrow, and unless first-order kinetics is assumed, an a priori knowledge of the reaction order is required. [3][4][5][6][7] The last requirement imposes a particular limitation for studies of gas electrodes since e]ectroconversion of gaseous reactants is often preceded by a nonlinear reversible adsorption step which is reflected in nonlinear kinetics. Detailed methods for the evaluation of RDE data in nonlinear cases are presented in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…Detailed methods for the evaluation of RDE data in nonlinear cases are presented in Ref. [2][3][4][5][6][7][8]. Suspension electrodes (SE) using a suspension of powder of the electrode material provide an alternative configuration that decreases diffusion effectsY ~ However, the experimental setup and the interpretation of the experimental findings are complex.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Investigation of the Kinetics and Mechanism of Co‐Porphyrin Catalyzed Oxygen Reduction by Hydrophobic Carbon‐Ceramic Electrodes

Tsionsky

Lev

1995

J. Electrochem. Soc.

View full text Add to dashboard Cite

The electrochemical mechanism of pyrolyzed carbon supported Co-tetramethoxymeso-porphyrin (Co-TMMP) catalysis of oxygen reduction is studied by a fuel-cell-type hydrephobic ceramic-carbon composite electrode (CCE), made of sot-gel-derived graphite-silica material. Only a thin layer at the outermost surface of the hydrephobic porous CCE is in contact with the electrolyte, thus minimizing effects of electrode structure on the current density. This property makes CCEs most useful for elucidation of kinetic mechanisms of gas electrodes. At low cathodic overpotentials, oxygen reduction in acidic solution on heat-treated Co-TMMP supported graphite powder exhibits first-order kinetics with respect to adsorbed all-oxygen, which obeys Langmuir adsorption isotherm. The activation energy of oxygen reduction equals 7.5 -+ 0.4 kcal/mol. Half-order oxygen dependence is observed at high overpotentials, and the reaction is limited by the rate of hydrogen peroxide conversion.

show abstract

In the Cathodic Reduction of Dioxygen in Aqueous Solution

Towl¹

1986

Inorganic Reactions and Methods

View full text Add to dashboard Cite

Systematische Untersuchung an Elektrokatalysatoren der Sauerstoffreduktion*

Cited by 22 publications

References 5 publications

Electrocatalytic oxygen reduction: the role of oxygen bridges as a structural factor in the activity of transition-metal phthalocyanines

Electrocatalytic oxygen reduction: the role of oxygen bridges as a structural factor in the activity of transition-metal phthalocyanines

Investigation of the Kinetics and Mechanism of Co‐Porphyrin Catalyzed Oxygen Reduction by Hydrophobic Carbon‐Ceramic Electrodes

In the Cathodic Reduction of Dioxygen in Aqueous Solution

Contact Info

Product

Resources

About