Electrocatalysis under a magnetic lens: A combined electrochemistry and electron paramagnetic resonance review

Hartog, Stephan den; Neukermans, Sander; Samanipour, Mohammad; Ching, H. Y. Vincent; Breugelmans, Tom; Hubin, Annick; Ustarroz, Jon

doi:10.1016/j.electacta.2021.139704

Cited by 16 publications

(9 citation statements)

References 101 publications

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“…The most popular techniques for free radical detection are electron paramagnetic resonance (EPR) spectroscopy − (also known as electron spin resonance (ESR) spectroscopy) and fluorescence spectroscopy. − EPR offers low limits of detection as well as accurate identification of different free radical species through distinctive splitting patterns and is often used in combination with electrochemical experiments. , Due to the extremely short lifetimes of many free radicals, particularly in aqueous solutions (e.g., HO · in water has a lifetime of ∼ μs), EPR spectroscopy often requires the use of spin trap reagents to convert the free radicals into more persistent species, which are stable over the timescale of the measurement.…”

Section: Introductionmentioning

confidence: 99%

Electron Paramagnetic Resonance for the Detection of Electrochemically Generated Hydroxyl Radicals: Issues Associated with Electrochemical Oxidation of the Spin Trap

et al. 2022

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For the detection of electrochemically produced hydroxyl radicals (HO • ) from the oxidation of water on a boron-doped diamond (BDD) electrode, electron paramagnetic resonance spectroscopy (EPR) in combination with spin trap labels is a popular technique. Here, we show that quantification of the concentration of HO • from water oxidation via spin trap electrochemical (EC)-EPR is problematic. This is primarily due to the spin trap oxidizing at potentials less positive than water, resulting in the same spin trap-OH • adduct as formed from the solution reaction of OH • with the spin trap. We illustrate this through consideration of 5,5-dimethyl-1-pyrroline Noxide (DMPO) as a spin trap for OH • . DMPO oxidation on a BDD electrode in an acidic aqueous solution occurs at a peak current potential of +1.90 V vs SCE; the current for water oxidation starts to rise rapidly at ca. +2.3 V vs SCE. EC-EPR spectra show signatures due to the spin trap adduct (DMPO-OH • ) at potentials lower than that predicted thermodynamically (for water/HO • ) and in the region for DMPO oxidation. Increasing the potential into the water oxidation region, surprisingly, shows a lower DMPO-OH • concentration than when the potential is in the DMPO oxidation region. This behavior is attributed to further oxidation of DMPO-OH • , production of fouling products on the electrode surface, and bubble formation. Radical scavengers (ethanol) and other spin traps, here N-tert-butyl-αphenylnitrone, α-(4-pyridyl N-oxide)-N-tert-butylnitrone, and 2-methyl-2-nitrosopropane dimer, also show electrochemical oxidation signals less positive than that of water on a BDD electrode. Such behavior also complicates their use for the intended application.

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Section: Introductionmentioning

confidence: 99%

Electron Paramagnetic Resonance for the Detection of Electrochemically Generated Hydroxyl Radicals: Issues Associated with Electrochemical Oxidation of the Spin Trap

et al. 2022

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“…Electrolytes by definition have high-dielectric constants; traditionally, this issue could be overcome by the use of flat cells to minimize the cross-section of the electrolyte, minimizing dielectric loss. 21 , 22 , 23 Electrochemical intermediates could then be studied by placing two electrodes on opposite ends of the cell, outside the cavity, such that generated species diffuse through the cavity during analysis. This setup is often used to study liquid-phase paramagnetic electrochemical intermediates ( Figure 2 A).…”

Section: Experimental Setups For Studying Electrocatalysts By Electro...mentioning

confidence: 99%

An overview of solid-state electron paramagnetic resonance spectroscopy for artificial fuel reactions

Bau¹,

Emwas²,

Rueping³

2022

iScience

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“…Owing to the fact that spin quantum number of the oxygen species between the OER/ORR reaction is not conserved, , the high energy barrier of OER/ORR is associated with the spin state transition involving spin electrons (from the singlet state of diamagnetic OH – /H 2 O to the triplet state of paramagnetic O 2 , Figure ). Therefore, the transition with a fixed spin state is normally prohibited in quantum mechanics, and it requires spin-related electron transfer and extra energy to drive, which spin modulation plays a critical role in reaction kinetics of oxygen electrocatalysis. − In addition, most of these TMCs with unpaired spin electrons always exhibit spin-related magnetism, which can be affected by magnetic field. − With the consideration of spin and magnetism, many efforts have been made to modulate the electronic spin of catalysts or build spin-selective channel to filter effective spin electrons by magnetic field, which are effective to accelerate the spin-related OER/ORR reaction …”

Section: Introductionmentioning

confidence: 99%

Spin-Modulated Oxygen Electrocatalysis

Fang,

Zhao,

Shen

et al. 2023

Precision Chemistry

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The electrocatalysis reactions involving oxygen, such as oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), play a critical role in energy storage/ conversion applications, e.g., fuel cells, metal-air batteries, and electrochemical water splitting. The high kinetic energy barrier of the OER/ORR is highly associated with the spin state interconversion between singlet OH − /H 2 O and triplet O 2 , which is influenced by the spin state and magnetism of catalysts. This Review summarizes recent progress and advances in understanding spin/magnetism-related effects in oxygen electrocatalysis to develop spin theory. It is demonstrated that the spin states (low, intermediate, and high spin) of magnetic transition metal catalysts (TMCs) can directly affect the reaction barriers of OER/ORR by tailoring the bonding of oxygen intermediates with TMCs. Besides, the spin states of TMCs can build a spin-selective channel to filter the electron spins required for the single/triplet interconversion of O species during OER/ORR. In this Review, we introduced many approaches to modulating spin state, for instance, altering the crystal field, oxidation state of active-site ions, and the morphology of TMCs. What's more, a magnetic field can drive the spin flip of magnetic ions to achieve the spin alignment (↑↑) (i.e., facilitating spin polarization), which will strengthen the spin selectivity for accelerating the filtration and transfer of the spins with the same direction for the generation and conversion of triplet ↑O�O↑. Importantly, the origin of magnetic field enhancement on OER/ORR are deeply discussed, which provides a great vision for the magnetism-assisted catalysis. Finally, the challenges and perspectives for future development of spin/magnetism catalysis are presented. This Review is expected to highlight the significance of spin/magnetism theory in breaking the bottleneck of electrocatalysis field and promote the development of high-efficientcy electrocatalysts for practical applications.

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Electrocatalysis under a magnetic lens: A combined electrochemistry and electron paramagnetic resonance review

Cited by 16 publications

References 101 publications

Electron Paramagnetic Resonance for the Detection of Electrochemically Generated Hydroxyl Radicals: Issues Associated with Electrochemical Oxidation of the Spin Trap

Electron Paramagnetic Resonance for the Detection of Electrochemically Generated Hydroxyl Radicals: Issues Associated with Electrochemical Oxidation of the Spin Trap

An overview of solid-state electron paramagnetic resonance spectroscopy for artificial fuel reactions

Spin-Modulated Oxygen Electrocatalysis

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