One-Electron and Two-Electron Transfers in Electrochemistry and Homogeneous Solution Reactions

Evans, Dennis H.

doi:10.1021/cr068066l

Cited by 345 publications

(358 citation statements)

References 286 publications

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“…Therefore, the Ni L-edge sXAS spectra show unambiguously that Ni 3+ is the stable intermediate state formed in the electrochemical reaction of the LiNi0.5Mn1.5O4 electrode. In other words, the electrochemical cycling of the LiNi0.5Mn1.5O4 electrode consists of two single electron transfer processes, which involves two redox couples, Ni 2+ /Ni 3+ and Ni 3+ /Ni 4+ that take place at very close potential 29 .…”

Section: Results Andmentioning

confidence: 99%

Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi_0.5Mn_1.5O₄ Electrodes

et al. 2015

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KEYWORDS: high voltage spinel, LiNi0.5Mn1.5O4, Ni(III), soft x-ray spectroscopy.2 ABSTRACT LiNi0.5Mn1.5O4 spinel is an appealing cathode material for next generation rechargeable Li-ion batteries due to its high operating voltage of ~4.7 V (vs. Li/Li + ). Although it is widely believed that the full range electrochemical cycling involves the redox of Ni(II)/(IV), it has not been experimentally clarified whether Ni(III) exists as the intermediate state, or a double-electron transfer takes place. Here, combined with theoretical calculations, we show unambiguous spectroscopic evidence of the Ni(III) state when the LiNi0.5Mn1.5O4 electrode is half charged.This provides a direct verification of single-electron-transfer reactions in LiNi0.5Mn1.5O4 upon cycling, namely, from Ni(II) to Ni(III), then to Ni(IV). Additionally, by virtue of its surface sensitivity, soft x-ray absorption spectroscopy also reveals the electrochemically inactive Ni 2+and Mn 2+ phases on the electrode surface. Our work provides the long-awaited clarification of the single-electron transfer mechanism in LiNi0.5Mn1.5O4 electrodes. Furthermore, the experimental results serve as a benchmark for further spectroscopic characterizations of Nibased battery electrodes.3

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Section: Results Andmentioning

confidence: 99%

Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi_0.5Mn_1.5O₄ Electrodes

et al. 2015

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“…53,54 In this case the one-electron oxidation product should be thermodynamically unstable to disproportionation: 2Bt…”

Section: ■ Discussionmentioning

confidence: 99%

Dynamics of Interfacial Electron Transfer from Betanin to Nanocrystalline TiO₂: The Pursuit of Two-Electron Injection

et al. 2015

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We report spectroelectrochemical and transient absorption spectroscopic studies of electron injection from the plant pigment betanin (Bt) to nanocrystalline TiO 2 . Spectroelectrochemical experiments and density functional theory (DFT) calculations are used to interpret transient absorption data in terms of excited state absorption of Bt and ground state absorption of oxidation intermediates and products. Comparison of the amplitudes of transient signals of Bt on TiO 2 and on ZrO 2 , for which no electron injection takes place, reveals the signature of two-electron injection from electronically excited Bt to TiO 2 . Transient signals observed for Bt on TiO 2 (in contrast to ZrO 2 ) on the nanosecond time scale reveal the spectral signatures of photo-oxidation products of Bt absorbing in the red and the blue. These are assigned to a oneelectron oxidation product formed by recombination of injected electrons with the two-electron oxidation product. We conclude that whereas electron injection is a simultaneous two-electron process, recombination is a one-electron process. The formation of a semiquinone radical through recombination limits the efficiency and long-term stability of the Bt-based dye-sensitized solar cell. Strategies are suggested for enhancing photocurrents of dye-sensitized solar cells by harnessing the two-electron oxidation of organic dye sensitizers.

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“…Electrochemical organic transformations are often used as an efficient way to perform complicated organic syntheses. Various aspects involved in the electrochemical synthesis of organic compounds, for example, mechanism of redox processes, kinetics of electrode reactions, homogeneous or heterogeneous electron transfers, coupled electron transfer processes, have been reviewed [98][99][100][101]. Redox processes also help design organic photovoltaic materials, which are cost effective compared to metal-based photovoltaic or fuel cell materials.…”

Section: Organicsmentioning

confidence: 99%

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

Arumugam

Becker

2014

Minerals

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Abstract:Applications of redox processes range over a number of scientific fields. This review article summarizes the theory behind the calculation of redox potentials in solution for species such as organic compounds, inorganic complexes, actinides, battery materials, and mineral surface-bound-species. Different computational approaches to predict and determine redox potentials of electron transitions are discussed along with their respective pros and cons for the prediction of redox potentials. Subsequently, recommendations are made for certain necessary computational settings required for accurate calculation of redox potentials. This article reviews the importance of computational parameters, such as basis sets, density functional theory (DFT) functionals, and relativistic approaches and the role that physicochemical processes play on the shift of redox potentials, such as hydration or spin orbit coupling, and will aid in finding suitable combinations of approaches for different chemical and geochemical applications. Identifying cost-effective and credible computational approaches is essential to benchmark redox potential calculations against experiments. Once a good theoretical approach is found to model the chemistry and thermodynamics of the redox and electron transfer process, this knowledge can be incorporated into models of more complex reaction mechanisms that include diffusion in the solute, surface diffusion, and dehydration, to name a few. This knowledge is important to fully understand the nature of redox processes be it a geochemical process that dictates natural redox reactions or one that is being used for the optimization of a chemical process in industry. In addition, it will help identify materials that will be useful to design catalytic OPEN ACCESSMinerals 2014, 4 346 redox agents, to come up with materials to be used for batteries and photovoltaic processes, and to identify new and improved remediation strategies in environmental engineering, for example the reduction of actinides and their subsequent immobilization. Highly under-investigated is the role of redox-active semiconducting mineral surfaces as catalysts for promoting natural redox processes. Such knowledge is crucial to derive process-oriented mechanisms, kinetics, and rate laws for inorganic and organic redox processes in nature. In addition, molecular-level details still need to be explored and understood to plan for safer disposal of hazardous materials. In light of this, we include new research on the effect of iron-sulfide mineral surfaces, such as pyrite and mackinawite, on the redox chemistry of actinyl aqua complexes in aqueous solution.

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One-Electron and Two-Electron Transfers in Electrochemistry and Homogeneous Solution Reactions

Cited by 345 publications

References 286 publications

Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi_0.5Mn_1.5O₄ Electrodes

Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi_0.5Mn_1.5O₄ Electrodes

Dynamics of Interfacial Electron Transfer from Betanin to Nanocrystalline TiO₂: The Pursuit of Two-Electron Injection

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

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One-Electron and Two-Electron Transfers in Electrochemistry and Homogeneous Solution Reactions

Cited by 345 publications

References 286 publications

Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi0.5Mn1.5O4 Electrodes

Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi0.5Mn1.5O4 Electrodes

Dynamics of Interfacial Electron Transfer from Betanin to Nanocrystalline TiO2: The Pursuit of Two-Electron Injection

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

Contact Info

Product

Resources

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Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi_0.5Mn_1.5O₄ Electrodes

Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi_0.5Mn_1.5O₄ Electrodes

Dynamics of Interfacial Electron Transfer from Betanin to Nanocrystalline TiO₂: The Pursuit of Two-Electron Injection