A Critical Assessment of Formula as a Figure of Merit for Oxygen Reduction Electrocatalysts in Aqueous Electrolytes

Georgescu, Nicholas S.; Jebaraj, Adriel Jebin Jacob; Scherson, Daniel Alberto

doi:10.1149/2.0021506eel

Cited by 9 publications

(10 citation statements)

References 15 publications

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Section: Introductionmentioning

confidence: 99%

“…and Georgescu et al. revisited the σ – ω −1/2 relationship with an effectively reduced reaction scheme . Intriguingly, the J and S values of an σ – ω −1/2 plot for the above‐mentioned studies could have different mathematical formalism for each of the presumed reaction schemes.…”

Section: Introductionmentioning

confidence: 99%

“…In fact, there are efforts to extendt he application of RRDE and gain further insights into the ORR mechanism by combining the online detection of reactioni ntermediates with the knowledge of diffusional current. [8][9][10][11] Damjanovic et al first proposed am ethodt oo btain the rate constantf or HO 2 À generation and the relative kinetics of direct four-electron( 4e) reductiono fO 2 and the generation of HO 2 À from ap lot of diskto-ringc urrentd ensity ratio (j D /j R , s)a gainst the reciprocal of the square-rooted electrode rotation rate (w À1/2 ). [8] Similarly, Wroblowa et al developedamore comprehensive reaction schemea nd demonstrated that the slope (S)a nd y-intercept( J) values of a s-w À1/2 plot could be very complicated and only qualitative information could be obtained from a J-S plot.…”

Section: Introductionmentioning

confidence: 99%

“…[9] Recently,Z hang et al and Georgescu et al revisited the s-w À1/2 relationship with an effectively reduced reaction scheme. [10,11] Intriguingly,t he J and S values of an s-w À1/2 plot for the above-mentioned studies could have different mathematical formalism for each of the presumed reaction schemes.M oreover,t he evaluation requires the s-w À1/2 plot to be linear.T his can be challengingi napractical analysis because this approach is highly sensitivet os urface roughness and slight electrode wobbling due to shaft eccentricity. [9,12] Certainly,a ne xtension to current analytical methodsf or the ORR is in demand and the approach hast ob ea ccurate, efficient, and generally feasible.…”

Section: Introductionmentioning

confidence: 99%

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An Extension to the Analytical Evaluation of the Oxygen Reduction Reaction Based On the Electrokinetics On a Rotating Ring–Disk Electrode

Wang

2016

ChemElectroChem

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The use of rotating ring–disk electrodes has become a general practice for evaluating the activity of the oxygen reduction reaction (ORR) performed with electrocatalysts. This technique typically employs simple equations based on the charge/mass balance to calculate the average number of electrons transferred and the percentage of peroxide production. However, the underlying mechanistic assumptions of this analysis and the uncertainty involved when considering the catalytic decomposition of HO2− have not been well elucidated. This work demonstrates through electrokinetic derivations that the conventional formalism presumes a stepwise ORR pathway and four reaction parameters in total are provided for indexing ORR activity. Furthermore, we provide a method of current density deconvolution to separate the individual reaction components and exemplify its use for Tafel analysis. Finally, we provide analytical solutions to the reaction parameters for the ORR when heterogeneous HO2− decomposition is involved.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Extension to the Analytical Evaluation of the Oxygen Reduction Reaction Based On the Electrokinetics On a Rotating Ring–Disk Electrode

Wang

2016

ChemElectroChem

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“…n e can be calculated using Eq. 4 52 after subtracting the background disk and ring currents from the observed disk and ring currents during the ORR.…”

Section: Effects Of Eg and Caprolactam Onmentioning

confidence: 99%

Effects of Ethylene Glycol and Caprolactam on the ORR and HOR Performances of Pt/C Catalysts

Zhai

St‐Pierre

2016

J. Electrochem. Soc.

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Ethylene glycol (EG) and caprolactam are two representative contaminant species either present in the fuel cell system or released by fuel cell system materials. The contamination effects of EG and caprolactam on the electro-catalytic performances of a Pt/C catalyst toward the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) were investigated in acid media using the rotating ring/disk electrode (RRDE) technique. The Pt surface coverage increased with EG and caprolactam concentrations. The H 2 O 2 yield also significantly increased because of the effects of the two contaminants. The EG-and caprolactam-derived adsorbates reduce the ORR and HOR rates and modify the rate-determining step (change in Tafel Considering the inevitable depletion of conventional fossil fuels and the release of greenhouse gases into the Earth's atmosphere, it is necessary to look for renewable and clean energy supplies. Proton exchange membrane fuel cells (PEMFCs) are promising as clean energy sources for future automotive applications. However, the performance and durability of PEMFCs can be significantly decreased by the presence of contaminants in air and hydrogen or released by fuel cell system materials.1-3 Such species may adsorb on the Pt catalyst, penetrate into the ionomer and membrane, or compete with the main reactions, which decreases the active surface area, ionic conductivity of the catalyst layer and membrane, and cell performance. 2,4-9In addition, H 2 O 2 , which is a side product of the oxygen reduction reaction (ORR), and its associated yield often increases in the presence of organic contaminants such as acetylene, acetonitrile, propene, naphthalene, and methyl methacrylate. 10-13 A larger H 2 O 2 generation rate exerts an undetermined effect on the performance and durability of PEMFCs. The formation of H 2 O 2 has been linked to the radical attack decomposition of the Nafion ionomer, which is accelerated by the presence of Fe 2+ and Cu 2+ ions. 14,15 The Nafion ionomer is used as an electrolyte membrane and added to the catalyst layer to exploit its binding property and improve catalyst utilization. Consequently, the decomposition of the Nafion ionomer is a significant risk to the PEMFC performance and durability. Therefore, it is necessary to investigate the ORR, hydrogen oxidation reaction (HOR), and H 2 O 2 yield in the presence of contaminants to understand their effects on PEMFCs.This study was initiated with a list of system contaminants identified by the National Renewable Energy Laboratory (NREL).16 These were separated into 2 classes: linear and more structurally complex molecules including cyclic molecules (ring-shaped). One molecule of each class was chosen for these initial studies. Ethylene glycol (EG) is interesting because it is widely used as a coolant, antifreeze agent, and de-icing solution. De-icing of airport runways and airplanes is the primary source of EG in the environment. EG is also dispersed in the environment by the disposal of products that contain it. In addition, 1,6...

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Selenourea-assisted synthesis of selenium-modified iridium catalysts: evaluation of their activity toward reduction of oxygen

Dembińska

Dobrzeniecka

Pisarek

et al. 2015

Electrochimica Acta

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A Critical Assessment of Formula as a Figure of Merit for Oxygen Reduction Electrocatalysts in Aqueous Electrolytes

Cited by 9 publications

References 15 publications

An Extension to the Analytical Evaluation of the Oxygen Reduction Reaction Based On the Electrokinetics On a Rotating Ring–Disk Electrode

An Extension to the Analytical Evaluation of the Oxygen Reduction Reaction Based On the Electrokinetics On a Rotating Ring–Disk Electrode

Effects of Ethylene Glycol and Caprolactam on the ORR and HOR Performances of Pt/C Catalysts

Selenourea-assisted synthesis of selenium-modified iridium catalysts: evaluation of their activity toward reduction of oxygen

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