Potentially Confusing: Potentials in Electrochemistry

Boettcher, Shannon W.; Oener, Sebastian Z.; Lonergan, Mark C.; Surendranath, Yogesh; Ardo, Shane; Brozek, Carl K.; Kempler, Paul A.

doi:10.1021/acsenergylett.0c02443

Cited by 126 publications

(101 citation statements)

References 4 publications

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“…This study combines spectroscopy with electrochemistry; thus, for readers of both fields to understand the results, it is important that a common language is established, and that it is clearly and carefully specified which potential is referred to. 3 To facilitate this, we will begin this discussion by presenting some important background and definitions that are necessary to correlate the electrochemical measurements to the APPES measurements.…”

Section: Discussionmentioning

confidence: 99%

“…The electrochemical potential of a charged species i in phase α is defined as the energy required to move the species from vacuum at infinity and add it to the phase. The electrochemical potential μ̅ i α is sometimes separated into one contribution from the chemical potential and one contribution from the electrostatic potential according to the following equation: 1 − 3 where μ i α is the chemical potential of species i in phase α, z is the unit charge, and ϕ α is the electrostatic potential of the phase. To facilitate the comparison to spectroscopy, μ i α and μ̅ i α are given in eV throughout the manuscript.…”

Section: Introductionmentioning

confidence: 99%

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Probing Electrochemical Potential Differences over the Solid/Liquid Interface in Li-Ion Battery Model Systems

Källquist

Lindgren

Lee

et al. 2021

ACS Appl. Mater. Interfaces

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The electrochemical potential difference (Δμ̅) is the driving force for the transfer of a charged species from one phase to another in a redox reaction. In Li-ion batteries (LIBs), Δμ̅ values for both electrons and Li-ions play an important role in the charge-transfer kinetics at the electrode/electrolyte interfaces. Because of the lack of suitable measurement techniques, little is known about how Δμ̅ affects the redox reactions occurring at the solid/liquid interfaces during LIB operation. Herein, we outline the relations between different potentials and show how ambient pressure photoelectron spectroscopy (APPES) can be used to follow changes in Δμ̅ e over the solid/liquid interfaces operando by measuring the kinetic energy (KE) shifts of the electrolyte core levels. The KE shift versus applied voltage shows a linear dependence of ∼1 eV/V during charging of the electrical double layer and during solid electrolyte interphase formation. This agrees with the expected results for an ideally polarizable interface. During lithiation, the slope changes drastically. We propose a model to explain this based on charge transfer over the solid/liquid interface.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Probing Electrochemical Potential Differences over the Solid/Liquid Interface in Li-Ion Battery Model Systems

Källquist

Lindgren

Lee

et al. 2021

ACS Appl. Mater. Interfaces

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“…A key caveat to interpreting this result is that optical absorption energies do not involve nuclear rearrangement in the excited state, while redox potentials are impacted by the nuclear motion associated with ion-pairing. 71 In other words, the stronger influence of harder Lewis acids may be borne out only when they can rearrange to bind more tightly. Instead, we propose that the Ti-based orbitals become stabilized by the larger lattices created by the softer Sr 2+ and Ba 2+ ions.…”

Section: Electrostatic Control Of Band Gap Energiesmentioning

confidence: 99%

Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites

Fabrizio¹,

Lazarou²,

Payne³

et al. 2021

Preprint

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<div> <div> <p>Titanium-based metal—organic frameworks (Ti-MOFs) attract intense research attention because they can store charges in the form of Ti3+ and they serve as photosensitizers for co-catalysts through heterogeneous photoredox reactions at the MOF-liquid interface. Both charge storage and charge transfer depend on redox potentials of the MOF and the molecular substrate, but the factors controlling these energetic aspects are not well understood. Additionally, photocatalysis involving Ti-MOFs relies on co-catalysts rather than the intrinsic Ti reactivity in part because Ti-MOFs with open metal sites are rare. Here, we report that the class of Ti-MOFs known as MUV-10 can be synthetically modified to include a range of redox-inactive ions with flexible coordination environments that control the energies of the photoactive orbitals. Lewis acidic cations installed in the MOF cluster (Cd, Sr , and Ba ) or introduced to the pores (H, Li, Na, K) tune the electronic structure and band gaps of the MOFs. Through use of optical redox indicators, we report the first direct measurement of the Fermi levels (redox potentials) of photoexcited MOFs in situ. Taken together, these results explain the ability of Ti-MOFs to store charges and provide design principles for achieving heterogeneous photoredox chemistry with electrostatic control.</p> </div> </div>

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“…This value is composed of the thermodynamic free energy requirement for the two half reactions (E Nernst Þ, the individual overpotentials for each half reaction (η), as well as additional energy losses (E s ), encompassing ohmic losses, diffusion energy losses, and other associated phenomena (Equation 1). [7][8][9][10]…”

Section: Introductionmentioning

confidence: 99%

“…The full cell potential (

E_{c e l l}

) is the voltage required to drive the overall reaction at a given current density and therefore represents the electrical energy input for a CO 2 ‐reduction cell. This value is composed of the thermodynamic free energy requirement for the two half reactions (

E_{N e r n s t})

, the individual overpotentials for each half reaction ( η ), as well as additional energy losses (

E_{σ}

), encompassing ohmic losses, diffusion energy losses, and other associated phenomena (Equation [7–10]

true E_{c e l l} = ([] E_{N e r n s t}^{a} + η_{a}) - ([] E_{N e r n s t}^{c} + η_{c}) + E_{σ}

…”

Section: Introductionmentioning

confidence: 99%

Advancing the Anode Compartment for Energy Efficient CO₂ Reduction at Neutral pH

et al. 2021

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Energy efficient CO 2 reduction in neutral pH requires the development of electrochemical devices operating with minimal energy input. To reach this objective, we propose an original approach focused on the anode compartment where the oxygen evolution reaction (OER) takes place. Different anode catalysts, anolytes and membranes were tested, and the components resulting in the most energy efficient and stable CO 2 reduction reaction device were selected. A stainless-steelbased anode with significant OER activity and stability in a wide pH range was used to compare symmetric (neutral catholyte and anolyte) and asymmetric (neutral catholyte and alkaline anolyte) configurations. The gain in energy efficiency for carbon products of 6-8 % in the asymmetric configuration highlighted the advantages of a pH gradient. Although a Nafion membrane gave the highest energy efficiencies, the pH was unstable. Therefore, bipolar membranes that can maintain a pH gradient emerge as the best option for long-term electrolysis. This work paves the way for the development of highly energy efficient CO 2 -reduction devices with cathodes operating in low pH conditions.

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Potentially Confusing: Potentials in Electrochemistry

Cited by 126 publications

References 4 publications

Probing Electrochemical Potential Differences over the Solid/Liquid Interface in Li-Ion Battery Model Systems

Probing Electrochemical Potential Differences over the Solid/Liquid Interface in Li-Ion Battery Model Systems

Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites

Advancing the Anode Compartment for Energy Efficient CO₂ Reduction at Neutral pH

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Potentially Confusing: Potentials in Electrochemistry

Cited by 126 publications

References 4 publications

Probing Electrochemical Potential Differences over the Solid/Liquid Interface in Li-Ion Battery Model Systems

Probing Electrochemical Potential Differences over the Solid/Liquid Interface in Li-Ion Battery Model Systems

Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites

Advancing the Anode Compartment for Energy Efficient CO2 Reduction at Neutral pH

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Advancing the Anode Compartment for Energy Efficient CO₂ Reduction at Neutral pH