Unconventional interfacial water structure of highly concentrated aqueous electrolytes at negative electrode polarizations

Li, Chao-Yu; Chen, Ming; Liu, Shuai; Lu, Xinyao; Meng, Jinhui; Yan, Jiawei; Abruña, Héctor D.; Feng, Guang; Lian, Tianquan

doi:10.1038/s41467-022-33129-8

Cited by 47 publications

(51 citation statements)

References 60 publications

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“…The basic HB structure of the bulk phase of Na 2 SO 3 solution with different mass fractions has been introduced in the first part of this work. In the aqueous solution system above metal electrode, the essence of the geometric structure of the EDL at the solid–liquid interface where the electrochemical reaction takes place is the HB network composed of water molecules and ions . Therefore, a thorough understanding of EDL structures is crucial for clarifying the electrode reaction mechanism and performance. , The analysis of the internal structure of the EDL is based on a full understanding of the corresponding HB structure, which is still a challenging topic. − To analyze the stability of the SO 3 2‑ ion at different adsorption sites, the geometry of the initial and stability configurations is shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…In the aqueous solution system above metal electrode, the essence of the geometric structure of the EDL at the solid−liquid interface where the electrochemical reaction takes place is the HB network composed of water molecules and ions. 39 Therefore, a thorough understanding of EDL structures is crucial for clarifying the electrode reaction mechanism and performance. 40,41 The analysis of the internal structure of the EDL is based on a full understanding of the corresponding HB structure, which is still a challenging topic.…”

Section: Adsorption Of Somentioning

confidence: 99%

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Spectroscopic and Simulation Insights into the Corrosion Mechanism of Sulfite on Titanium

Meng

Yan

et al. 2022

J. Phys. Chem. B

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Ion adsorption and hydrogen bond (HB) network reconstruction in electric double layer (EDL) have a profound impact on the interface properties. The microstructure in the bulk phase of 1.00–21.30 wt.% Na2SO3 aqueous solutions are investigated by X-ray scattering, confocal Raman spectroscopy, and classical molecular dynamics. The electronic properties of SO3 2‑ adsorption and the geometric structure of the HB network in the EDL at the titanium TiO2(101) surface are studied by density functional theory (DFT) and classical molecular dynamics. The SO3 2– strongly weakens the fully hydrogen-bonded water (FHW) and transforms it into partial hydrogen-bonded water (PHW). The HB transformation index (HBTI = PHW/FHW) shows a linear relationship with the mass fraction of Na2SO3. The TiOb-parallel adsorption configuration of SO3 2‑ enhances the ionicity of the Ob–Ti6 bond, resulting in the formation of oxygen vacancies at the titanium passive film surface. Besides, SO3 2‑ and Na+ are enriched and thermodynamic supersaturated in the inner Helmholtz layer (IHL), and the ions are diluted in the outer Helmholtz layer (OHL). The diffusion coefficient of SO3 2‑ and water molecules in EDL decreases seriously, which is easy to causes salt scaling on the surface of titanium passive film. This work provides evidence for the destruction of titanium passive film by SO3 2‑.

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Section: Resultsmentioning

confidence: 99%

Section: Adsorption Of Somentioning

confidence: 99%

Spectroscopic and Simulation Insights into the Corrosion Mechanism of Sulfite on Titanium

Meng

Yan

et al. 2022

J. Phys. Chem. B

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“…Classical MD (CMD) has been widely used to investigate the concentrated electrolytes, and can offer microscopic information on solvation structures of concentrated electrolytes and electrode/electrolyte interfaces. ,, Careful parametrization is essential to ensure the accuracy of the CMD simulations, and even so, CMD may not give reliable results in difficult cases such as highly concentrated electrolytes . To avoid the uncertainty in force field parameters and more importantly compute the redox potential of TFSI – , AIMD is used to calculate concentrated electrolytes in this work. , …”

Section: Methods Sectionmentioning

confidence: 99%

“…Recently, lots of efforts have been devoted to understanding the interfacial structures of WiSE on anode surface and how they affect the SEI formation. − For example, Lian et al found that the interfacial water can not serve as H-bond acceptors but donors due to the coordination of Li + , which provides atomistic insight into desolvation process and layered accumulation of Li + on anode surface . On the other hand, it should be noted that the bulk thermodynamics (e.g., reduction potential of TFSI – in bulk solution) determines whether the SEI would form at the first place in the initial charging cycle.…”

Section: Introductionmentioning

confidence: 99%

Switching of Redox Levels Leads to High Reductive Stability in Water-in-Salt Electrolytes

2023

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Developing nonflammable electrolytes with wide electrochemical windows is of great importance for energy storage devices. Water-in-salt electrolytes (WiSE) have attracted great interests due to their widely opened electrochemical windows and high stability. Previous theoretical investigations have revealed changes in solvation shell of water molecules result in opening of HOMO–LUMO gaps of water, leading to the formation of an anion-derived solid-electrolyte-interphase (SEI) in WiSE. However, how solvation structures affect electrochemical windows at atomic level is still a puzzle, which hinders optimization and design of aqueous electrolytes. Herein, machine learning molecular dynamics and free energy calculation method are applied to compute redox potentials of anions of Li-salts and water of aqueous electrolytes at a range of salt concentrations. Furthermore, an analysis based on local solvation structures is employed to demonstrate the structure–property relations. Our calculation shows that the hydrogen evolution reaction is impeded in WiSE due to switching of the order of redox levels of the anion and H2O, leading to formation of SEI and high reductive stability. Level switching is caused by the special solvation environments of isolated water molecules. Our work provides new insight into the electrochemistry of aqueous electrolytes which would benefit the electrolyte design in energy storage devices.

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“…[42][43][44][45] Furthermore, recent studies have shown that highly concentrated electrolytes exhibit an unusual interfacial H2O structure. 44,46 Therefore, highly concentrated electrolytes can be used to uncover the role of H2O in controlling kinetic branching between the C1 and C2+ pathways without the use of an organic co-solvent.…”

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confidence: 99%

Promoting Cu Catalyzed CO2 electroreduction to multi-carbon products by tuning the activity of H2O

Zhang

Gao

Hall

2022

Preprint

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The electrochemical reduction of CO2 to multi-carbon products is a sustainable route for the synthesis of energy dense chemical feedstocks. Cu is the only material known to produce multi-carbon (C2+) products with appreciable selectivity. However, the generation of C2+ products compete with the formation of C1 products and the reduction of H2O to hydrogen. Here, we tuned the activity of H2O from 0.97 to 0.47 by using a NaClO4-based H2O-in-salt-electrolyte. Commercial Cu-nanoparticle electrodes evaluated in pH 9 NaClO4 with a H2O activity of 0.66 achieved a Faradaic Efficiency of ~ 73% for C2+ products (ethylene, ethanol, and propanol) with a C2+ partial current density of −110 mA cm–2 at –0.88 vs. Reversible Hydrogen Electrode. Furthermore, we were able to modulate the C2+/C1 ratios between 1 to 20 by altering only the H2O activity, demonstrating unrivaled tunability between C1 and C2+ products. Analysis of the Tafel slopes and reaction orders on model Cu electrodes revealed that the mechanism for forming C2 products was unchanged across a wide range of H2O activities, while C1 products and H2 had mechanisms which changed as the activity of H2O was lowered. Therefore, we can conclude that protons are part of the rate-determining step for the formation of C1 products, but not C2 products. We have demonstrated that tuning the activity of H2O in an aqueous solvent is a powerful new guiding principle for improving the reduction of CO2 to C2 and C3 products.

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Unconventional interfacial water structure of highly concentrated aqueous electrolytes at negative electrode polarizations

Cited by 47 publications

References 60 publications

Spectroscopic and Simulation Insights into the Corrosion Mechanism of Sulfite on Titanium

Spectroscopic and Simulation Insights into the Corrosion Mechanism of Sulfite on Titanium

Switching of Redox Levels Leads to High Reductive Stability in Water-in-Salt Electrolytes

Promoting Cu Catalyzed CO2 electroreduction to multi-carbon products by tuning the activity of H2O

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