The chemistry of superoxide ion

Sawyer, Donald T.; Gibian, Morton J.

doi:10.1016/0040-4020(79)80032-0

Cited by 229 publications

(63 citation statements)

References 64 publications

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“…Hence, for example, during a typical photocatalytic oxidation of organic pollutants on TiO 2 in aqueous solutions, the reacting holes are scavenged either directly by the pollutant or by adsorbed hydroxyl ions to produced hydroxyl radicals which can then oxidize the pollutant due to their high oxidizing power. Simultaneously, the photogenerated electrons reduce molecular oxygen to a superoxide radical (E O2/O2 −• = −0.16 V versus NHE [130]) which can then undergo further reactions to produce hydroxyl radicals [17,[131][132][133][134]. It is obvious that the positions of the conduction and valence band edges are of crucial importance here since these give information on the reductive and oxidative power of photogenerated electrons and holes, respectively.…”

Section: Introductionmentioning

confidence: 99%

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO₂‐Based Nanomaterials

Beránek

2011

Advances in Physical Chemistry

341

183

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TiO 2 -based nanomaterials play currently a major role in the development of novel photochemical systems and devices. One of the key parameters determining the photoactivity of TiO 2 -based materials is the position of the band edges. Although its knowledge is an important prerequisite for understanding and optimizing the performance of photochemical systems, it has been often rather neglected in recent research, particularly in the field of heterogeneous photocatalysis. This paper provides a concise account of main methods for the determination of the position of the band edges, particularly those suitable for measurements on nanostructured materials. In the first part, a survey of key photophysical and photochemical concepts necessary for understanding the energetics at the semiconductor/solution interface is provided. This is followed by a detailed discussion of several electrochemical, photoelectrochemical, and spectroelectrochemical methods that can be applied for the determination of band edge positions in compact and nanocrystalline thin films, as well as in nanocrystalline powders.

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Section: Introductionmentioning

confidence: 99%

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO₂‐Based Nanomaterials

Beránek

2011

Advances in Physical Chemistry

341

183

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“…The fabricated Na−O 2 cells consisted of a sodium metal anode and freestanding vertically aligned few-walled CNT carpets (detailed preparation of the nanotubes has been previously reported 39,50 ) as the O 2 electrode (∼1 × 1 cm). The electrodes were vacuum-dried at 100°C for 8 h and transferred to a glovebox (H 2 O < 0.1 ppm, O 2 < 0.1 ppm, Mbraun, USA) without exposure to the ambient environment.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

Rate-Dependent Nucleation and Growth of NaO₂ in Na–O₂ Batteries

Ortiz‐Vitoriano

Batcho²,

Kwabi³

et al. 2015

J. Phys. Chem. Lett.

111

161

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Understanding the oxygen reduction reaction kinetics in the presence of Na ions and the formation mechanism of discharge product(s) is key to enhancing Na− O 2 battery performance. Here we show NaO 2 as the only discharge product from Na− O 2 cells with carbon nanotubes in 1,2-dimethoxyethane from X-ray diffraction and Raman spectroscopy. Sodium peroxide dihydrate was not detected in the discharged electrode with up to 6000 ppm of H 2 O added to the electrolyte, but it was detected with ambient air exposure. In addition, we show that the sizes and distributions of NaO 2 can be highly dependent on the discharge rate, and we discuss the formation mechanisms responsible for this rate dependence. Micron-sized (∼500 nm) and nanometer-scale (∼50 nm) cubes were found on the top and bottom of a carbon nanotube (CNT) carpet electrode and along CNT sidewalls at 10 mA/g, while only micron-scale cubes (∼2 μm) were found on the top and bottom of the CNT carpet at 1000 mA/g, respectively.R echargeable metal-air (oxygen) batteries are receiving intense interest as possible alternatives to lithium-ion batteries, in particular due to their potential to provide higher gravimetric energies.1−5 While much attention has been focused on aprotic Li−O 2 batteries since their introduction in 1996 by Abraham et al.,6 substantial challenges must be addressed before widespread commercial exploitation is possible. These include the instability of aprotic electrolytes 7−9 and oxygen electrodes, 10,11 which contribute to low round-trip efficiency, poor rate capability, and poor cycle life. Recently, a metal-air battery in which lithium has been replaced by sodium has received increasing attention. Unfortunately, the factors responsible for dissimilar discharge product chemistry and morphologies are still unclear, and no correlation has been found between the type of air electrode or electrolyte and the discharge product formed. Because the discharge product crystal structure, morphology (e.g., shape and thickness), and distribution are important parameters that influence the voltage profile on discharge and charge, the rate capability, the discharge capacity, and the reversibility in metalair batteries, 23 it is critical to gain insights into the oxygen reduction kinetics in the presence of Na ions and the nucleation and growth mechanisms of discharge products.In this study, we investigate discharged Na−O 2 cells with carbon nanotube (CNT) carpet cathodes to understand the effect of discharge kinetics on the formation of the discharge product. We analyzed the chemical composition of the discharge product using X-ray diffraction (XRD) and Raman spectroscopy and found that it consisted solely of NaO 2 . The formation of Na 2 O 2 ·H 2 O was not readily detected with the addition of water to the solvent (<6000 ppm); however, the evolution of Na 2 O 2 ·2H 2 O was detected when we intentionally exposed the sample to the ambient environment. We also observed rate-dependent effects on the size and distribution of the discharge product. ...

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“…The kinetics of O 2 reduction in the presence of strongly coordinating Li + are sluggish (Supporting Information, Figure S1), and its elementary steps are not well understood. O 2 reduction proceeds first by the formation of superoxide (O 2 À ) [9,10] and then lithium superoxide (Li…”

mentioning

confidence: 99%

Experimental and Computational Analysis of the Solvent‐Dependent O₂/Li⁺‐O₂⁻ Redox Couple: Standard Potentials, Coupling Strength, and Implications for Lithium–Oxygen Batteries

et al. 2016

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The chemistry of superoxide ion

Cited by 229 publications

References 64 publications

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO₂‐Based Nanomaterials

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO₂‐Based Nanomaterials

Rate-Dependent Nucleation and Growth of NaO₂ in Na–O₂ Batteries

Experimental and Computational Analysis of the Solvent‐Dependent O₂/Li⁺‐O₂⁻ Redox Couple: Standard Potentials, Coupling Strength, and Implications for Lithium–Oxygen Batteries

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The chemistry of superoxide ion

Cited by 229 publications

References 64 publications

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO2‐Based Nanomaterials

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO2‐Based Nanomaterials

Rate-Dependent Nucleation and Growth of NaO2 in Na–O2 Batteries

Experimental and Computational Analysis of the Solvent‐Dependent O2/Li+‐O2− Redox Couple: Standard Potentials, Coupling Strength, and Implications for Lithium–Oxygen Batteries

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(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO₂‐Based Nanomaterials

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO₂‐Based Nanomaterials

Rate-Dependent Nucleation and Growth of NaO₂ in Na–O₂ Batteries

Experimental and Computational Analysis of the Solvent‐Dependent O₂/Li⁺‐O₂⁻ Redox Couple: Standard Potentials, Coupling Strength, and Implications for Lithium–Oxygen Batteries