Investigations of Electrochemically Active Regions in Bifunctional Air Electrodes Using Partially Immersed Platinum Electrodes

Ikezawa, Atsunori; Miyazaki, Kohei; Fukutsuka, Tomokazu; Abe, Takeshi

doi:10.1149/2.0971508jes

Cited by 14 publications

(6 citation statements)

References 23 publications

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“…Typical bifunctional catalysts used in oxygen electrodes include platinum [13] palladium [9] and non-noble metal compound phases, such as perovskites, [ 14 ] spinels, [ 15 , 16 ] and pyrochlores [17]. Perovskite catalysts mixed with high surface area carbon are some of the most promising bifunctional catalyst materials produced to date but reported data varies depending on the type of perovskite and operational conditions.…”

Section: Introductionmentioning

confidence: 99%

A high-performance, bifunctional oxygen electrode catalysed with palladium and nickel-iron hexacyanoferrate

McKerracher

Figueredo-Rodríguez

León

et al. 2016

Electrochimica Acta

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The development of air-breathing cathodes, which utilise atmospheric oxygen, enables the construction of lightweight, high energy density metal-air batteries and fuel cells. Air electrodes can be very lightweight and thin because the active material, oxygen, does not need to be stored inside the cell. However, air electrodes are restricted by poor reaction kinetics and low activity of many catalysts towards the oxygen evolution and reduction reactions. In addition, it is a challenge to maintain chemical and mechanical stability of the catalyst and supporting materials at oxidising currents under the strong alkaline conditions commonly used, and gas evolution. This paper reports a novel bifunctional oxygen electrode with remarkable stability, able to perform at current densities up to 1,000 mA cm -2 and withstand 3,000 cycles continuously. The electrode is catalysed by a mixture of Pd/C and mixed nickel-iron hexocyanoferrate, which have high activities towards the ORR and OER reactions, respectively.

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Section: Introductionmentioning

confidence: 99%

A high-performance, bifunctional oxygen electrode catalysed with palladium and nickel-iron hexacyanoferrate

McKerracher

Figueredo-Rodríguez

León

et al. 2016

Electrochimica Acta

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“…[25][26][27][28][29] Quite recently, high O 2 solubility in some ILs has been utilized to address the issues of insufficient O 2 concentration near the Pt surface. Snyder et al pioneered the studies of using ILs as an ORR promoter.…”

mentioning

confidence: 99%

“…22 Ionic liquids (ILs) have been studied as a non-aqueous reaction media for electrochemical applications due to their low volatility, wide electrochemical windows, good ionic conductivity, and good chemical stability. [25][26][27][28][29] Quite recently, high O 2 solubility in some ILs has been utilized to address the issues of insufficient O 2 concentration near the Pt surface. Snyder et al pioneered the studies of using ILs as an ORR promoter.…”

mentioning

confidence: 99%

Enhancing Pt/C Catalysts for the Oxygen Reduction Reaction with Protic Ionic Liquids: The Effect of Anion Structure

Huang¹,

Song

Morales‐Collazo

et al. 2017

J. Electrochem. Soc.

139

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Protic ionic liquids (ILs) have been recently studied as a potential approach to enhance oxygen reduction reaction (ORR) activity of carbon supported platinum catalysts (Pt/C) for application in polymer electrolyte membrane fuel cells. The high oxygen solubility in the ILs was suggested as one of the main reasons for the accelerated reaction rates. Because the nature of the anion of the IL has been associated with increased oxygen solubility, in this work we survey a number of ionic liquids with various anions to study this effect. While the search for direct correlation between the ORR activities and the oxygen solubilities does not produce any conclusive results, by contrast, the specific activity showed dependence on the availability of oxygenated species free Pt sites. This finding indicates that the inhibition of Pt oxidation and less adsorption of non-reactive species may also play an important role in the enhanced ORR activity. Moreover, the degree of IL coverage on the Pt surface was estimated using (bi)sulfate ions as an indicator. The surface coverage not only affected the ORR activity, but also the Pt dissolution process. This suggests that an optimal balance between activity and stability can be achieved on a partially covered Pt surface. The oxygen reduction reaction (ORR) that occurs on the cathode poses a major hurdle for the efficient utilization of polymer electrolyte fuel cells (PEMFC). Extensive studies have focused on developing novel catalysts to improve the efficiency of this reaction.1,2 The ORR involves multiple steps, among which O 2 + H + + e − ↔ OOH ads and OH ads + H + + e − ↔ H 2 O act as the potential rate determining steps. Simultaneously optimizing the Gibbs free energies for both steps to completely eliminate the overpotential is very challenging, and a ∼350 mV overpotenial is commonly observed, which is independent of the identity of the catalyst.3,4 The large overpotential has been generally attributed to the sluggish kinetics of the ORR and adsorption of oxygenated species (e.g. OH ad ) or other anions. 5 The coverage of the adsorbed oxygenated species (θ OH ad ) is unfavorable for the reaction, and the availability of the free metal surface (as expressed by the (1-θ OH ad ) term) is one of the governing factors for the ORR activity.6,7 As a result, much effort has been dedicated to weakening the bonding of OH to the catalyst surface either by shifting the d-band center of Pt 8,9 or by lateral repulsion from the supports (e.g. metal oxides). 10,11Anion adsorption on Pt also affects the ORR activity, and it is agreed that the occupation of active sites deactivates the sites and reduces the activity.12 In real-world membrane-electrode assembly (MEA), the Nafion membrane and ionomer, constituted by a Teflon-like backbone and an anionic cluster of sulfonic groups, 13 are widely employed as indispensable components. The interface between the Nafion and the metal has received great attention due to the strong irreversible sulfonate anions adsorption on the Pt. 12,[14][15][16] The de...

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“…However, it has been well documented that Pt/C alone is not an efficient bifunctional electrocatalyst because of its insufficient OER performances [84][85][86]. To address the primary challenges of OER, metals such as Au [8,87,88], Co [89], Zn [90], Ir [7,91], Pd [91], and Ru [91] have been used to form carbon-supported Pt-alloy catalysts in various metal-air batteries.…”

Section: Composites Of Carbon and Pt Or Pt-alloysmentioning

confidence: 99%

A Review of Carbon-Composited Materials as Air-Electrode Bifunctional Electrocatalysts for Metal–Air Batteries

Wang

Fang

Zhang

et al. 2018

Electrochem. Energ. Rev.

190

101

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Metal-air batteries (MABs), particularly rechargeable MABs, have gained renewed interests as a potential energy storage/conversion solution due to their high specific energy, low cost, and safety. The development of MABs has, however, been considerably hampered by its relatively low rate capability and its lack of efficient and stable air catalysts in which the former stems mainly from the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) and the latter stems from the corrosion/oxidation of carbon materials in the presence of oxygen and high electrode potentials. In this review, various carbon-composited bifunctional electrocatalysts are reviewed to summarize progresses in the enhancement of ORR/OER and durability induced by the synergistic effects between carbon and other component(s). Catalyst mechanisms of the reaction processes and associated performance enhancements as well as technical challenges hindering commercialization are also analyzed. To facilitate further research and development, several research directions for overcoming these challenges are also proposed.

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Investigations of Electrochemically Active Regions in Bifunctional Air Electrodes Using Partially Immersed Platinum Electrodes

Cited by 14 publications

References 23 publications

A high-performance, bifunctional oxygen electrode catalysed with palladium and nickel-iron hexacyanoferrate

A high-performance, bifunctional oxygen electrode catalysed with palladium and nickel-iron hexacyanoferrate

Enhancing Pt/C Catalysts for the Oxygen Reduction Reaction with Protic Ionic Liquids: The Effect of Anion Structure

A Review of Carbon-Composited Materials as Air-Electrode Bifunctional Electrocatalysts for Metal–Air Batteries

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