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Sanz Matias A, Roncoroni F, Sundararaman S, Prendergast D. Ca-dimers, solvent layering, and dominant electrochemically active species in Ca(BH 4) 2 in THF. Nat Commun 2024; 15:1397. [PMID: 38360965 PMCID: PMC11258298 DOI: 10.1038/s41467-024-45672-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 02/01/2024] [Indexed: 02/17/2024] Open
Abstract
Divalent ions (Mg, Ca, and Zn) are being considered as competitive, safe, and earth-abundant alternatives to Li-ion electrochemistry, but present challenges for stable cycling due to undesirable interfacial phenomena. We explore the formation of electroactive species in the electrolyte Ca(BH4)2∣THF using molecular dynamics coupled with a continuum model of bulk and interfacial speciation. Free-energy analysis and unsupervised learning indicate a majority population of neutral Ca dimers and monomers with diverse molecular conformations and an order of magnitude lower concentration of the primary electroactive charged species - the monocation, CaBH[Formula: see text] - produced via disproportionation of neutral complexes. Dense layering of THF molecules within ~1 nm of the electrode surface strongly modulates local electrolyte species populations. A dramatic increase in monocation population in this interfacial zone is induced at negative bias. We see no evidence for electrochemical activity of fully-solvated Ca2+. The consequences for performance are discussed in light of this molecular-scale insight.
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Affiliation(s)
- Ana Sanz Matias
- Joint Center for Energy Storage Research, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Fabrice Roncoroni
- Joint Center for Energy Storage Research, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Siddharth Sundararaman
- Joint Center for Energy Storage Research, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - David Prendergast
- Joint Center for Energy Storage Research, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
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2
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Kim M, Tetteh EB, Savan A, Xiao B, Ludwig A, Schuhmann W, Chung TD. Reorganization energy in a polybromide ionic liquid measured by scanning electrochemical cell microscopy. J Chem Phys 2023; 158:134707. [PMID: 37031154 DOI: 10.1063/5.0143018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
Abstract
Room temperature ionic liquids (RT-ILs) are promising electrolytes for electrocatalysis. Understanding the effects of the electrode–electrolyte interface structure on electrocatalysis in RT-ILs is important. Ultrafast mass transport of redox species in N-methyl- N-ethyl-pyrrolidinium polybromide (MEPBr2n+1) enabled evaluation of the reorganization energy ( λ), which reflects the solvation structure in the inner Helmholtz plane (IHP). λ was achieved by fitting the electron transfer rate-limited voltammogram at a Pt ultramicroelectrode (UME) to the Marcus–Hush–Chidsey model for heterogeneous electron transfer kinetics. However, it is time-consuming or even impossible to prepare electrode materials, including alloys of numerous compositions in the form of UME, for each experiment. Herein, we report a method to evaluate the λ of MEPBr2n+1 by scanning electrochemical cell microscopy (SECCM), which allows high throughput electrochemical measurements using a single electrode with high spatial resolution. Fast mass transport in the nanosized SECCM tip is critical for achieving heterogeneous electron transfer-limited voltammograms. Furthermore, investigating λ on a high-entropy alloy materials library composed of Pt, Pd, Ru, Ir, and Ag suggests a negative correlation between λ and the work function. Given that the potential of zero charge correlates with the work function of electrodes, this can be attributed to the surface-charge sensitive ionic structure in the IHP of MEPBr2n+1, modulating the solvation energy of the redox-active species in the IHP.
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Affiliation(s)
- Moonjoo Kim
- Department of Chemistry, Seoul National University, Seoul 08826, Republic of Korea
- Analytical Chemistry – Center for Electrochemical Sciences (CES), Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstraße 150, Bochum, Germany
| | - Emmanuel Batsa Tetteh
- Analytical Chemistry – Center for Electrochemical Sciences (CES), Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstraße 150, Bochum, Germany
| | - Alan Savan
- Chair for Materials Discovery and Interfaces, Institute for Materials, Faculty of Mechanical Engineering, Ruhr University Bochum, Universitätsstraße 150, Bochum, Germany
| | - Bin Xiao
- Chair for Materials Discovery and Interfaces, Institute for Materials, Faculty of Mechanical Engineering, Ruhr University Bochum, Universitätsstraße 150, Bochum, Germany
| | - Alfred Ludwig
- Chair for Materials Discovery and Interfaces, Institute for Materials, Faculty of Mechanical Engineering, Ruhr University Bochum, Universitätsstraße 150, Bochum, Germany
- ZGH, Ruhr University Bochum, Universitätsstraße 150, Bochum, Germany
| | - Wolfgang Schuhmann
- Analytical Chemistry – Center for Electrochemical Sciences (CES), Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstraße 150, Bochum, Germany
| | - Taek Dong Chung
- Department of Chemistry, Seoul National University, Seoul 08826, Republic of Korea
- Advanced Institute of Convergence Technology, Suwon-si, Gyeonggi-do 16229, Republic of Korea
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3
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Levey KJ, Edwards MA, White HS, Macpherson JV. Simulation of the cyclic voltammetric response of an outer-sphere redox species with inclusion of electrical double layer structure and ohmic potential drop. Phys Chem Chem Phys 2023; 25:7832-7846. [PMID: 36857676 DOI: 10.1039/d3cp00098b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
A finite-element model has been developed to simulate the cyclic voltammetric (CV) response of a planar electrode for a 1e outer-sphere redox process, which fully accounts for cell electrostatics, including ohmic potential drop, ion migration, and the structure of the potential-dependent electric double layer. Both reversible and quasi-reversible redox reactions are treated. The simulations compute the time-dependent electric potential and ion distributions across the entire cell during a voltammetric scan. In this way, it is possible to obtain the interdependent faradaic and non-faradaic contributions to a CV and rigorously include all effects of the electric potential distribution on the rate of electron transfer and the local concentrations of the redox species Oz and Rz-1. Importantly, we demonstrate that the driving force for electron transfer can be different to the applied potential when electrostatic interactions are included. We also show that the concentrations of Oz and Rz-1 at the plane of electron transfer (PET) significantly depart from those predicted by the Nernst equation, even when the system is characterised by fast electron transfer/diffusion control. A mechanistic rationalisation is also presented as to why the electric double layer has a negligible effect on the CV response of such reversible systems. In contrast, for quasi-reversible electron transfer the concentrations of redox species at the PET are shown to play an important role in determining CV wave shape, an effect also dependant on the charge of the redox species and the formal electrode potential of the redox couple. Failure to consider electrostatic effects could lead to incorrect interpretation of electron-transfer kinetics from the CV response. Simulated CVs at scan rates between 0.1 and 1000 V s-1 are found to be in good agreement with experimental data for the reduction of 1.0 mM Ru(NH3)63+ at a 2 mm diameter gold disk electrode in 1.0 M potassium nitrate.
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Affiliation(s)
- Katherine J Levey
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK. .,Centre for Diamond Science and Technology, University of Warwick, Coventry, CV4 7AL, UK
| | - Martin A Edwards
- Department of Chemistry & Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Henry S White
- Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, UT 84112, USA.
| | - Julie V Macpherson
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK. .,Centre for Diamond Science and Technology, University of Warwick, Coventry, CV4 7AL, UK
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4
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Weiß LJK, Music E, Rinklin P, Banzet M, Mayer D, Wolfrum B. On-Chip Electrokinetic Micropumping for Nanoparticle Impact Electrochemistry. Anal Chem 2022; 94:11600-11609. [PMID: 35900877 DOI: 10.1021/acs.analchem.2c02017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Single-entity electrochemistry is a powerful technique to study the interactions of nanoparticles at the liquid-solid interface. In this work, we exploit Faradaic (background) processes in electrolytes of moderate ionic strength to evoke electrokinetic transport and study its influence on nanoparticle impacts. We implemented an electrode array comprising a macroscopic electrode that surrounds a set of 62 spatially distributed microelectrodes. This configuration allowed us to alter the global electrokinetic transport characteristics by adjusting the potential at the macroscopic electrode, while we concomitantly recorded silver nanoparticle impacts at the microscopic detection electrodes. By focusing on temporal changes of the impact rates, we were able to reveal alterations in the macroscopic particle transport. Our findings indicate a potential-dependent micropumping effect. The highest impact rates were obtained for strongly negative macroelectrode potentials and alkaline solutions, albeit also positive potentials lead to an increase in particle impacts. We explain this finding by reversal of the pumping direction. Variations in the electrolyte composition were shown to play a critical role as the macroelectrode processes can lead to depletion of ions, which influences both the particle oxidation and the reactions that drive the transport. Our study highlights that controlled on-chip micropumping is possible, yet its optimization is not straightforward. Nevertheless, the utilization of electro- and diffusiokinetic transport phenomena might be an appealing strategy to enhance the performance in future impact-based sensing applications.
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Affiliation(s)
- Lennart J K Weiß
- Neuroelectronics - Munich Institute of Biomedical Engineering, Department of Electrical Engineering, TUM School of Computation, Information and Technology, Technical University of Munich, Boltzmannstrasse 11, Garching 85748, Germany
| | - Emir Music
- Neuroelectronics - Munich Institute of Biomedical Engineering, Department of Electrical Engineering, TUM School of Computation, Information and Technology, Technical University of Munich, Boltzmannstrasse 11, Garching 85748, Germany
| | - Philipp Rinklin
- Neuroelectronics - Munich Institute of Biomedical Engineering, Department of Electrical Engineering, TUM School of Computation, Information and Technology, Technical University of Munich, Boltzmannstrasse 11, Garching 85748, Germany
| | - Marko Banzet
- Institute of Biological Information Processing, Bioelectronics (IBI-3), Forschungszentrum Jülich, Jülich 52425, Germany
| | - Dirk Mayer
- Institute of Biological Information Processing, Bioelectronics (IBI-3), Forschungszentrum Jülich, Jülich 52425, Germany
| | - Bernhard Wolfrum
- Neuroelectronics - Munich Institute of Biomedical Engineering, Department of Electrical Engineering, TUM School of Computation, Information and Technology, Technical University of Munich, Boltzmannstrasse 11, Garching 85748, Germany
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5
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Balu B, Khair AS. The electrochemical impedance spectrum of asymmetric electrolytes across low to moderate frequencies. J Electroanal Chem (Lausanne) 2022. [DOI: 10.1016/j.jelechem.2022.116222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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6
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Lissaneddine A, Pons MN, Aziz F, Ouazzani N, Mandi L, Mousset E. A critical review on the electrosorption of organic compounds in aqueous effluent - Influencing factors and engineering considerations. ENVIRONMENTAL RESEARCH 2022; 204:112128. [PMID: 34600882 DOI: 10.1016/j.envres.2021.112128] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/10/2021] [Accepted: 09/22/2021] [Indexed: 06/13/2023]
Abstract
Despite being an old process from the end of the 19th century, electrosorption has attracted renewed attention in recent years because of its unique properties and advantages compared to other separation technologies and due to the concomitant development of new porous electrode materials. Electrosorption offer the advantage to separate the pollutants from wastewater with the possibility of selectively adsorbing and desorbing the targeted compounds. A comprehensive review of electrosorption is provided with particular attention given to the electrosorption of organic compounds, unlike existing capacitive deionization review papers that only focus on inorganic salts. The background and principle of electrosorption are first presented, while the influence of the main parameters (e.g., electrode materials, electrode potential, physico-chemistry of the electrolyte solutions, type of compounds, co-sorption effect, reactor design, etc.) is then detailed and the modeling and engineering aspects are discussed. Finally, the main output and future prospects about recovery studies and combination between electro-sorption/desorption and degradation processes are given. This review particularly highlights that carbon-based materials have been mostly employed (85% of studies) as porous electrode in organics electrosorption, while existing studies lack of electrode stability and durability tests in real conditions. These electrodes have been implemented in a fixed-bed reactor design most of the time (43% of studies) due to enhanced mass transport. Moreover, the electrode potential is a major criterion: it should be applied in the non-faradaic domain otherwise unwanted reactions can easily occur, especially the corrosion of carbon from 0.21 V/standard hydrogen electrode or the water oxidation/reduction. Furthermore, there is lack of studies performed with actual effluents and without addition of supporting electrolyte, which is crucial for testing the real efficiency of the process. The associated predictive model will be required by considering the matrix effect along with transport phenomena and physico-chemical characteristics of targeted organic compounds.
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Affiliation(s)
- Amina Lissaneddine
- Université de Lorraine, CNRS, LRGP, F-54000, Nancy, France; National Center for Research and Studies on Water and Energy (CNEREE), Cadi Ayyad University, B. 511, 40000, Marrakech, Morocco; Laboratory of Water, Biodiversity, and Climate Change, Faculty of Sciences Semlalia, Cadi Ayyad University, B.P. 2390, 40000, Marrakech, Morocco
| | | | - Faissal Aziz
- National Center for Research and Studies on Water and Energy (CNEREE), Cadi Ayyad University, B. 511, 40000, Marrakech, Morocco; Laboratory of Water, Biodiversity, and Climate Change, Faculty of Sciences Semlalia, Cadi Ayyad University, B.P. 2390, 40000, Marrakech, Morocco
| | - Naaila Ouazzani
- National Center for Research and Studies on Water and Energy (CNEREE), Cadi Ayyad University, B. 511, 40000, Marrakech, Morocco; Laboratory of Water, Biodiversity, and Climate Change, Faculty of Sciences Semlalia, Cadi Ayyad University, B.P. 2390, 40000, Marrakech, Morocco
| | - Laila Mandi
- National Center for Research and Studies on Water and Energy (CNEREE), Cadi Ayyad University, B. 511, 40000, Marrakech, Morocco; Laboratory of Water, Biodiversity, and Climate Change, Faculty of Sciences Semlalia, Cadi Ayyad University, B.P. 2390, 40000, Marrakech, Morocco
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7
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Tunable angle-dependent electrochemistry at twisted bilayer graphene with moiré flat bands. Nat Chem 2022; 14:267-273. [PMID: 35177786 DOI: 10.1038/s41557-021-00865-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Accepted: 11/22/2021] [Indexed: 11/09/2022]
Abstract
Tailoring electron transfer dynamics across solid-liquid interfaces is fundamental to the interconversion of electrical and chemical energy. Stacking atomically thin layers with a small azimuthal misorientation to produce moiré superlattices enables the controlled engineering of electronic band structures and the formation of extremely flat electronic bands. Here, we report a strong twist-angle dependence of heterogeneous charge transfer kinetics at twisted bilayer graphene electrodes with the greatest enhancement observed near the 'magic angle' (~1.1°). This effect is driven by the angle-dependent tuning of moiré-derived flat bands that modulate electron transfer processes with the solution-phase redox couple. Combined experimental and computational analysis reveals that the variation in electrochemical activity with moiré angle is controlled by a structural relaxation of the moiré superlattice at twist angles of <2°, and 'topological defect' AA stacking regions, where flat bands are localized, produce a large anomalous local electrochemical enhancement that cannot be accounted for by the elevated local density of states alone.
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8
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Kostiuchenko Z, Cui JZ, Lemay SG. Electrochemistry in Micro- and Nanochannels Controlled by Streaming Potentials. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:2656-2663. [PMID: 32030113 PMCID: PMC6996092 DOI: 10.1021/acs.jpcc.9b08584] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 12/20/2019] [Indexed: 06/10/2023]
Abstract
Fluid and charge transport in micro- and nanoscale fluidic systems are intrinsically coupled via electrokinetic phenomena. While electroosmotic flows and streaming potentials are well understood for externally imposed stimuli, charge injection at electrodes localized inside fluidic systems via electrochemical processes remains to a large degree unexplored. Here, we employ ultramicroelectrodes and nanogap electrodes to study the subtle interplay between ohmic drops, streaming currents, and faradaic processes in miniaturized channels at low concentrations of supporting electrolyte. We show that electroosmosis can, under favorable circumstances, counteract the effect of ohmic losses and shift the apparent formal potential of redox reactions. This interplay can be described by simple circuit models, such that the results described here can be adapted to other micro- and nanofluidic electrochemical systems.
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9
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Edwards MA, Robinson DA, Ren H, Cheyne CG, Tan CS, White HS. Nanoscale electrochemical kinetics & dynamics: the challenges and opportunities of single-entity measurements. Faraday Discuss 2019; 210:9-28. [PMID: 30264833 DOI: 10.1039/c8fd00134k] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The development of nanoscale electrochemistry since the mid-1980s has been predominately coupled with steady-state voltammetric (i-E) methods. This research has been driven by the desire to understand the mechanisms of very fast electrochemical reactions, by electroanalytical measurements in small volumes and unusual media, including in vivo measurements, and by research on correlating electrocatalytic activity, e.g., O2 reduction reaction, with nanoparticle size and structure. Exploration of the behavior of nanoelectrochemical structures (nanoelectrodes, nanoparticles, nanogap cells, etc.) of a characteristic dimension λ using steady-state i-E methods generally relies on the well-known relationship, λ2 ∼ Dt, which relates diffusional lengths to time, t, through the coefficient, D. Decreasing λ, by performing measurements at a nanometric length scales, results in a decrease in the effective timescale of the measurement, and provides a direct means to probe the kinetics of steps associated with very rapid electrochemical reactions. For instance, steady-state voltammetry using a nanogap twin-electrode cell of characteristic width, λ ∼ 10 nm, allows investigations of events occurring at timescales on the order of ∼100 ns. Among many other advantages, decreasing λ also increases spatial resolution in electrochemical imaging, e.g., in scanning electrochemical microscopy, and allows probing of the electric double layer. This Introductory Lecture traces the evolution and driving forces behind the "λ2 ∼ Dt" steady-state approach to nanoscale electrochemistry, beginning in the late 1950s with the introduction of the rotating ring-disk electrode and twin-electrode thin-layer cells, and evolving to current-day investigations using nanoelectrodes, scanning nanocells for imaging, nanopores, and nanoparticles. The recent focus on so-called "single-entity" electrochemistry, in which individual and very short redox events are probed, is a significant departure from the steady-state approach, but provides new opportunities to probe reaction dynamics. The stochastic nature of very fast single-entity events challenges current electrochemical methods and modern electronics, as illustrated using recent experiments from the authors' laboratory.
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Affiliation(s)
- M A Edwards
- Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, USA.
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10
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Bae JH, Wang D, Hu K, Mirkin MV. Surface-Charge Effects on Voltammetry in Carbon Nanocavities. Anal Chem 2019; 91:5530-5536. [PMID: 30977642 DOI: 10.1021/acs.analchem.9b00426] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Ion transport controlled by electrostatic interactions is an important phenomenon in biological and artificial membranes, channels, and nanopores. Here, we employ carbon-coated nanopipets (CNPs) for studying permselective electrochemistry in a conductive nanopore. A significant accumulation (up to 2000-fold) of cationic redox species and anion depletion inside a CNP by diffuse-layer and surface-charge effects in a solution of low ionic strength were observed as well as the shift of the voltammetric midpeak potential. Finite-element simulations of electrostatic effects on CNP voltammograms show permselective ion transport in a single conducting nanopore and semiquantitatively explain our experimental data. The reported results are potentially useful for improving sensitivity and selectivity of CNP sensors for ionic analytes.
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Affiliation(s)
- Je Hyun Bae
- Department of Chemistry and Biochemistry , Queens College , Flushing , New York 11367 , United States
| | - Dengchao Wang
- Department of Chemistry and Biochemistry , Queens College , Flushing , New York 11367 , United States
| | - Keke Hu
- Department of Chemistry and Biochemistry , Queens College , Flushing , New York 11367 , United States.,The Graduate Center of CUNY , New York , New York 10016 , United States
| | - Michael V Mirkin
- Department of Chemistry and Biochemistry , Queens College , Flushing , New York 11367 , United States.,The Graduate Center of CUNY , New York , New York 10016 , United States
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11
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Kwon SR, Fu K, Han D, Bohn PW. Redox Cycling in Individually Encapsulated Attoliter-Volume Nanopores. ACS NANO 2018; 12:12923-12931. [PMID: 30525454 DOI: 10.1021/acsnano.8b08693] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Redox cycling electrochemistry in arrays of individually encapsulated attoliter-volume ( V ∼ 10 aL) nanopores is investigated and reported here. These nanopore electrode array (NEA) structures exhibit distinctive electrochemical behaviors not observed in open NEAs, which allow free diffusion of redox couples between the nanopore interior and bulk solution. Confined nanopore environments, generated by sealing NEAs with a layer of poly(dimethylsiloxane), are characterized by enhanced currents-up to 250-fold compared with open NEAs-owing to effective trapping of the redox couple inside the nanopores and to enhanced mass transport effects. In addition, electrochemical rectification ( ca. 1.5-6.3) was observed and is attributed to ion migration. Finite-element simulations were performed to characterize the concentration and electric potential gradients associated with the disk electrode, aqueous medium, and ring electrode inside the nanopores, and the results are consistent with experimental observations. The additional signal enhancement and redox-cycling-based rectification behaviors produced in these self-confined attoliter-volume nanopores are potentially useful in devising ultrasensitive sensors and molecular-based iontronic devices.
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Affiliation(s)
| | | | - Donghoon Han
- Department of Chemistry , The Catholic University of Korea , Bucheon-si , Gyeonggi-do 14662 , Republic of Korea
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12
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Hirata K, Kitagawa T, Miyazawa K, Okamoto T, Fukunaga A, Takatoh C, Fukuma T. Visualizing charges accumulated in an electric double layer by three-dimensional open-loop electric potential microscopy. NANOSCALE 2018; 10:14736-14746. [PMID: 30042993 DOI: 10.1039/c8nr03600d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Charges accumulated in an electric double layer (EDL) play key roles in various interfacial phenomena and electronic devices. However, direct imaging of their spatial distribution has been a great challenge, which has hindered our nano-level understanding of the mechanisms of such interfacial phenomena and functions. In this study, we present direct imaging of charges accumulated at an electrode-electrolyte interface using three-dimensional open-loop electric potential microscopy (3D-OL-EPM). Conventional OL-EPM allows us to visualize two-dimensional potential distributions in liquid yet the zero of the measured potential is not well defined due to the influence of the long-range (LR) interaction between the cantilever and the sample. Here, we present practical ways to reduce such an influence by improving the equation for the potential calculation and subtracting the LR contribution estimated from a Z potential profile. These improvements enabled the calibration of the measured potential values with respect to the bulk solution potential. With these improvements, we visualized opposite charge accumulation behaviors on a polarizable and non-polarizable electrode with a varying electrode potential. Combining OL-EPM with a 3D tip scanning method, we also performed a 3D-OL-EPM measurement on a Cu fine wire and visualized the nanoscale distribution of the charges accumulated at the interface. Such real-space information on the charge distributions in an EDL should provide valuable insights into the mechanisms of interfacial phenomena and functions that are important in various academic and industrial research on electronic devices, electrochemistry, tribology and life sciences.
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Affiliation(s)
- Kaito Hirata
- Division of Electrical Engineering and Computer Science, Kanazawa University, Kakuma-machi, 920-1192 Kanazawa, Japan.
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13
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Double layer effects in voltammetric measurements with scanning electrochemical microscopy (SECM). J Electroanal Chem (Lausanne) 2018. [DOI: 10.1016/j.jelechem.2017.10.044] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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14
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Bae JH, Yu Y, Mirkin MV. Diffuse Layer Effect on Electron-Transfer Kinetics Measured by Scanning Electrochemical Microscopy (SECM). J Phys Chem Lett 2017; 8:1338-1342. [PMID: 28286950 DOI: 10.1021/acs.jpclett.7b00161] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Recent theoretical and experimental studies revealed strong effects of the electrical double layer (EDL) on mass transfer at nanometer-sized electrodes and in electrochemical nanogaps. Although the EDL effect is much stronger in weakly supported media, it can significantly influence the kinetics of electron-transfer processes involving multicharged ionic redox species, even at high concentrations of supporting electrolyte. We measured the kinetics of Fe(CN)64- oxidation in 1 M KCl solution at the Pt nanoelectrode used as a tip in the scanning electrochemical microscope. The apparent standard rate constant values extracted from tip voltammograms without double-layer correction increased markedly with the decreasing separation distance between the tip and substrate electrodes. The same steady-state voltammograms were fitted to the theory including the EDL effect and yielded the rate constant essentially independent of the separation distance.
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Affiliation(s)
- Je Hyun Bae
- Department of Chemistry and Biochemistry, Queens College , Flushing, New York 11367, United States
| | - Yun Yu
- Department of Chemistry and Biochemistry, Queens College , Flushing, New York 11367, United States
- The Graduate Center of CUNY , New York, New York 10016, United States
| | - Michael V Mirkin
- Department of Chemistry and Biochemistry, Queens College , Flushing, New York 11367, United States
- The Graduate Center of CUNY , New York, New York 10016, United States
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15
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Yu Y, Sun T, Mirkin MV. Toward More Reliable Measurements of Electron-Transfer Kinetics at Nanoelectrodes: Next Approximation. Anal Chem 2016; 88:11758-11766. [DOI: 10.1021/acs.analchem.6b03392] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Yun Yu
- Department of Chemistry and
Biochemistry, Queens College-CUNY, Flushing, New York 11367, United States
- The Graduate Center, CUNY, New York, New York 10016, United States
| | - Tong Sun
- Department of Chemistry and
Biochemistry, Queens College-CUNY, Flushing, New York 11367, United States
- The Graduate Center, CUNY, New York, New York 10016, United States
| | - Michael V. Mirkin
- Department of Chemistry and
Biochemistry, Queens College-CUNY, Flushing, New York 11367, United States
- The Graduate Center, CUNY, New York, New York 10016, United States
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16
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Affiliation(s)
- Je Hyun Bae
- Department of Chemistry and Biochemistry; Queens College-CUNY, Flushing; New York 11367 USA
| | - Yun Yu
- Department of Chemistry and Biochemistry; Queens College-CUNY, Flushing; New York 11367 USA
- The Graduate Center; City University of New York; New York NY 10016 USA
| | - Michael V. Mirkin
- Department of Chemistry and Biochemistry; Queens College-CUNY, Flushing; New York 11367 USA
- The Graduate Center; City University of New York; New York NY 10016 USA
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Ma C, Xu W, Wichert WRA, Bohn PW. Ion Accumulation and Migration Effects on Redox Cycling in Nanopore Electrode Arrays at Low Ionic Strength. ACS NANO 2016; 10:3658-64. [PMID: 26910572 DOI: 10.1021/acsnano.6b00049] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Ion permselectivity can lead to accumulation in zero-dimensional nanopores, producing a significant increase in ion concentration, an effect which may be combined with unscreened ion migration to improve sensitivity in electrochemical measurements, as demonstrated by the enormous current amplification (∼2000-fold) previously observed in nanopore electrode arrays (NEA) in the absence of supporting electrolyte. Ionic strength is a key experimental factor that governs the magnitude of the additional current amplification (AFad) beyond simple redox cycling through both ion accumulation and ion migration effects. Separate contributions from ion accumulation and ion migration to the overall AFad were identified by studying NEAs with varying geometries, with larger AFad values being achieved in NEAs with smaller pores. In addition, larger AFad values were observed for Ru(NH3)6(3/2+) than for ferrocenium/ferrocene (Fc(+)/Fc) in aqueous solution, indicating that coupling efficiency in redox cycling can significantly affect AFad. While charged species are required to observe migration effects or ion accumulation, poising the top electrode at an oxidizing potential converts neutral species to cations, which can then exhibit current amplification similar to starting with the cation. The electrical double layer effect was also demonstrated for Fc/Fc(+) in acetonitrile and 1,2-dichloroethane, producing AFad up to 100× at low ionic strength. The pronounced AFad effects demonstrate the advantage of coupling redox cycling with ion accumulation and migration effects for ultrasensitive electrochemical measurements.
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Affiliation(s)
- Chaoxiong Ma
- Department of Chemistry and Biochemistry and ‡Department of Chemical and Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Wei Xu
- Department of Chemistry and Biochemistry and ‡Department of Chemical and Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - William R A Wichert
- Department of Chemistry and Biochemistry and ‡Department of Chemical and Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Paul W Bohn
- Department of Chemistry and Biochemistry and ‡Department of Chemical and Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States
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Tan SY, Zhang J, Bond AM, Macpherson JV, Unwin PR. Impact of Adsorption on Scanning Electrochemical Microscopy Voltammetry and Implications for Nanogap Measurements. Anal Chem 2016; 88:3272-80. [PMID: 26877069 DOI: 10.1021/acs.analchem.5b04715] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Sze-yin Tan
- Department
of Chemistry, University of Warwick, Coventry, West Midlands CV4 7AL, United Kingdom
- School
of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Jie Zhang
- School
of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Alan M. Bond
- School
of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Julie V. Macpherson
- Department
of Chemistry, University of Warwick, Coventry, West Midlands CV4 7AL, United Kingdom
| | - Patrick R. Unwin
- Department
of Chemistry, University of Warwick, Coventry, West Midlands CV4 7AL, United Kingdom
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Stout RF, Khair AS. Moderately nonlinear diffuse-charge dynamics under an ac voltage. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:032305. [PMID: 26465471 DOI: 10.1103/physreve.92.032305] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Indexed: 06/05/2023]
Abstract
The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of V_{o}/(k_{B}T/e), where V_{o} is the amplitude of the driving voltage and k_{B}T/e is the thermal voltage with k_{B} as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D/λ_{D}L, where D is the ion diffusivity, λ_{D} is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O(V_{o}^{3}) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in V_{o}. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing V_{o}. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.
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Affiliation(s)
- Robert F Stout
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Aditya S Khair
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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20
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Xiong J, Chen Q, Edwards MA, White HS. Ion Transport within High Electric Fields in Nanogap Electrochemical Cells. ACS NANO 2015; 9:8520-8529. [PMID: 26190513 DOI: 10.1021/acsnano.5b03522] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Ion transport near an electrically charged electrolyte/electrode interface is a fundamental electrochemical phenomenon that is important in many electrochemical energy systems. We investigated this phenomenon using lithographically fabricated thin-layer electrochemical cells comprising two Pt planar electrodes separated by an electrolyte of nanometer thickness (50-200 nm). By exploiting redox cycling amplification, we observed the influence of the electric double layer on transport of a charged redox couple within the confined electrolyte. Nonclassical steady-state peak shaped voltammograms for redox cycling of the ferrocenylmethyltrimethylammonium redox couple (FcTMA(+/2+)) at low concentrations of supporting electrolyte (≤10 mM) results from electrostatic interactions between the redox ions and the charged Pt electrodes. This behavior contrasts to sigmoidal voltammograms with a diffusion-limited plateau observed in the same electrochemical cells in the presence of sufficient electrolyte to screen the electrode surface charge (200 mM). Moreover, steady-state redox cycling was depressed significantly within the confined electrolyte as the supporting electrolyte concentration was decreased or as the cell thickness was reduced. The experimental results are in excellent agreement with predictions from finite-element simulations coupling the governing equations for ion transport, electric fields, and the redox reactions. Double layer effects on ion transport are generally anticipated in highly confined electrolyte and may have implications for ion transport in thin layer and nanoporous energy storage materials.
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Affiliation(s)
- Jiewen Xiong
- Department of Chemistry, University of Utah , 315 S 1400 E, Salt Lake City, Utah 84112, United States
| | - Qianjin Chen
- Department of Chemistry, University of Utah , 315 S 1400 E, Salt Lake City, Utah 84112, United States
| | - Martin A Edwards
- Department of Chemistry, University of Utah , 315 S 1400 E, Salt Lake City, Utah 84112, United States
| | - Henry S White
- Department of Chemistry, University of Utah , 315 S 1400 E, Salt Lake City, Utah 84112, United States
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21
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Batchelor-McAuley C, Kätelhön E, Barnes EO, Compton RG, Laborda E, Molina A. Recent Advances in Voltammetry. ChemistryOpen 2015; 4:224-60. [PMID: 26246984 PMCID: PMC4522172 DOI: 10.1002/open.201500042] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Indexed: 11/10/2022] Open
Abstract
Recent progress in the theory and practice of voltammetry is surveyed and evaluated. The transformation over the last decade of the level of modelling and simulation of experiments has realised major advances such that electrochemical techniques can be fully developed and applied to real chemical problems of distinct complexity. This review focuses on the topic areas of: multistep electrochemical processes, voltammetry in ionic liquids, the development and interpretation of theories of electron transfer (Butler-Volmer and Marcus-Hush), advances in voltammetric pulse techniques, stochastic random walk models of diffusion, the influence of migration under conditions of low support, voltammetry at rough and porous electrodes, and nanoparticle electrochemistry. The review of the latter field encompasses both the study of nanoparticle-modified electrodes, including stripping voltammetry and the new technique of 'nano-impacts'.
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Affiliation(s)
- Christopher Batchelor-McAuley
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of OxfordSouth Parks Road, Oxford, OX1 3QZ, UK
| | - Enno Kätelhön
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of OxfordSouth Parks Road, Oxford, OX1 3QZ, UK
| | - Edward O Barnes
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of OxfordSouth Parks Road, Oxford, OX1 3QZ, UK
| | - Richard G Compton
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of OxfordSouth Parks Road, Oxford, OX1 3QZ, UK
| | - Eduardo Laborda
- Departamento de Química Física, Facultad de Química, Regional Campus of International Excellence ‘Campus Mare Nostrum’, Universidad de Murcia30100, Murcia, Spain
| | - Angela Molina
- Departamento de Química Física, Facultad de Química, Regional Campus of International Excellence ‘Campus Mare Nostrum’, Universidad de Murcia30100, Murcia, Spain
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