Training of metrologists in Belorussia

Tarasevich, V. A.

doi:10.1007/bf00815950

Cited by 12 publications

(20 citation statements)

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“…In either case, the rate determining step appears to be the addition of the first electron to O 2,ad . The rate expression is then [2,[30][31][32],…”

Section: Reaction Pathwaymentioning

confidence: 99%

“…where n is the number of electrons, K is the chemical rate constant, c O 2 is the concentration of O 2 in the solution, H ad is the total surface coverage by all adsorbed species, x is either 1 or 2 depending on the site requirements of the adsorbates, i is the observed current, E is the applied potential, b and c are the symmetry factors (assumed to be ), and rH ad is parameter characterizing the rate of change of the apparent standard free energy of adsorption with the surface coverage by adsorbing species. Assuming that the coverage of ORR intermediates is small under reaction conditions [31], for most cases, only two adsorbed species need to be considered, OH ad and specifically adsorbing anions like (bi)sulfate or halides. In the following sections, we will use this reaction pathway and rate expression to analyze the effects of various factors on the kinetics of the ORR on Pt(hkl) surfaces.…”

Section: Reaction Pathwaymentioning

confidence: 99%

“…The first correlation between the kinetics of the ORR and the surface coverage of chemisorbed oxygen-containing species, historically termed ªoxideº, was established on a polycrystalline platinum electrode. In this study Tarasevich [31] proposed that both transition in the Tafel slope and the adsorption of O 2 is controlled by the surface coverage of chemisorbed oxygen-containing species. Very recently, by eliminating the surface heterogeneity of a polycrystalline Pt electrode with single crystal electrodes, Markovic et al, [4] gained new insight into the relationships between the surface coverage of platinum ªoxidesº and the kinetics of the ORR.…”

Section: Structure Sensitivity Of the Orr And Implications For Crystamentioning

confidence: 99%

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Oxygen Reduction Reaction on Pt and Pt Bimetallic Surfaces: A Selective Review

et al. 2001

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In this review we selectively summarize recent progress, primarily from our laboratory, in the development of the oxygen reduction reaction (ORR) catalysis on well‐defined surfaces. The focus is on two type of metallic surfaces: platinum single crystals and bimetallic surfaces based on platinum. The single crystal results provide insight into the effects of the platinum structure on the kinetics of the ORR, and create a fundamental link between the specific activity of Pt (rate per unit area) and particle size (for various particle shapes). The results show that the structure sensitive kinetics of the ORR arise primarily due to structure sensitive adsorption of anions. In the absence of specific adsorption, such as in Nafion polymer electrolyte, no particle size effect is expected. The knowledge of the electrocatalysis of the ORR on model bimetallic surfaces on Pt‐Ni and Pt‐Co bulk alloys was used to resolve the enhanced ORR kinetics on supported Pt‐Ni and Pt‐Co catalysts. Finally, we show that the ORR on platinum modified with pseudomorphic Pd metal film in alkaline solution is the best catalysts ever used in O2 reduction. For both bimetallic systems, we demonstrated that the ability to make a controlled and well characterized arrangement of two elements in the electrode surface region presage a new era of advances in the ORR electrocatalysis.

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“…In either case, the rate determining step appears to be the addition of the first electron to O 2,ad . The rate expression is then [2,[30][31][32],…”

Section: Reaction Pathwaymentioning

confidence: 99%

Section: Reaction Pathwaymentioning

confidence: 99%

Section: Structure Sensitivity Of the Orr And Implications For Crystamentioning

confidence: 99%

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Oxygen Reduction Reaction on Pt and Pt Bimetallic Surfaces: A Selective Review

et al. 2001

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“…Oxygen reduction (OR) at Pt electrodes usually occurs at oxide film-free surfaces (12)(13)(14)(15)(16). However, in early studies of this reaction, it was observed that at anodically pretreated electrodes, a Tafel relationship for the OR at oxidecovered surfaces can be established, providing measurements are taken quickly after anodic pretreatment (9,17).…”

mentioning

confidence: 99%

On the Kinetics and Mechanism of O 2 Reduction at Oxide Film Covered Pt Electrodes: I . Effect of Oxide Film Thickness on Kinetics

Damjanović¹,

Hudson²

1988

J. Electrochem. Soc.

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Oxygen reduction reaction is examined at oxide-covered Pt electrodes in acid solutions. In the high current density region characterized by the Tafel slope of -120 mV, the reaction is affected by the thickness of the oxide film. As the film thickness increases, current at the same potential decreases. In the low current density region characterized by the Tafel slope of -60 mV, the rate of reduction is unaffected by film thickness. In both current density regions, the potential at a given current decreases 60 mV as pH increases one unit. This leads to the fractional reaction order of 1/2 with respect to H~O + in the high current density region. In the low current density region, the order is 1. Possible mechanisms compatible with the observed kinetic parameters are discussed.

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“…Generally, on FePc-PcFe, FePc-PcCo and FePc catalysts, two Tafel slope regions including a high overpotential region (E < 0.6 V vs. RHE) and a low-overpotential region (E > 0.6 V vs. RHE) could be observed in Figure 6a.Damjanovic [28] explained that different slopes are dependent on different oxygen-containing species adsorption with the low-overpotential region being Temkin adsorption and the high overpotential region being Langmuir adsorption with decreasing coverage. Tarasevich [29] explained that this behavior was due to a change in the surface coverage of the chemisorbed oxygen-containing species. In addition, this phenomenon is commonly described as a site-blocking effect caused by oxygen-containing species at high potentials, and thus, the Tafel slope deviates from its value at lower potentials.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical and Spectroscopic Study of Homo‐ and Hetero‐Dimetallic Phthalocyanines as Catalysts for the Oxygen Reduction Reaction in Acidic Media

et al. 2018

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Metallophthalocyanines (MPc, M=Fe or Co) have been investigated extensively as a typical type of transition metal macrocyclic catalysts for the oxygen reduction reaction (ORR). However, the understanding about ORR catalyzed by binuclear even heterodimetallic phthalocyanines in acidic condition is still not sufficient. Herein we synthesized two homodimetallicphthalocyanine (FePc‐PcFe and CoPc‐PcCo) and a heterodimetallic phthalocyanine (FePc‐PcCo). The electrocatalytic activity of as‐synthesized compounds were characterized by cyclic voltammetry (CV) and rotating disk electrode (RDE). Generally, the binuclear metallophthalocyanines show higher activity than their monomeric analogues including FePc and CoPc. Also, the Fe compounds exhibit better catalytic performance than the Co phthalocyanines. However, interestingly the heterodimetallic phthalocyanine FePc‐PcCo shows similar half‐wave potential and ORR activity with FePc‐PcFe, rather than CoPc‐PcCo. This may be explained by XPS and XAS, which reveal a similar square‐planar structure existed in FePc‐PcCo and FePc‐PcFe and a non‐planar structure in CoPc‐PcCo. Furthermore, the increasing of the ORR activity among those five catalysts is well in agreement with the descending LUMO energies in DFT calculations. A lower LUMO energy indicates a favorable adsorption of O2, which in turn affects the ORR performance.

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Training of metrologists in Belorussia

Cited by 12 publications

References 0 publications

Oxygen Reduction Reaction on Pt and Pt Bimetallic Surfaces: A Selective Review

Oxygen Reduction Reaction on Pt and Pt Bimetallic Surfaces: A Selective Review

On the Kinetics and Mechanism of O 2 Reduction at Oxide Film Covered Pt Electrodes: I . Effect of Oxide Film Thickness on Kinetics

Electrochemical and Spectroscopic Study of Homo‐ and Hetero‐Dimetallic Phthalocyanines as Catalysts for the Oxygen Reduction Reaction in Acidic Media

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