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Santana Santos C, Jaato BN, Sanjuán I, Schuhmann W, Andronescu C. Operando Scanning Electrochemical Probe Microscopy during Electrocatalysis. Chem Rev 2023; 123:4972-5019. [PMID: 36972701 PMCID: PMC10168669 DOI: 10.1021/acs.chemrev.2c00766] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
Scanning electrochemical probe microscopy (SEPM) techniques can disclose the local electrochemical reactivity of interfaces in single-entity and sub-entity studies. Operando SEPM measurements consist of using a SEPM tip to investigate the performance of electrocatalysts, while the reactivity of the interface is simultaneously modulated. This powerful combination can correlate electrochemical activity with changes in surface properties, e.g., topography and structure, as well as provide insight into reaction mechanisms. The focus of this review is to reveal the recent progress in local SEPM measurements of the catalytic activity of a surface toward the reduction and evolution of O2 and H2 and electrochemical conversion of CO2. The capabilities of SEPMs are showcased, and the possibility of coupling other techniques to SEPMs is presented. Emphasis is given to scanning electrochemical microscopy (SECM), scanning ion conductance microscopy (SICM), electrochemical scanning tunneling microscopy (EC-STM), and scanning electrochemical cell microscopy (SECCM).
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Affiliation(s)
- Carla Santana Santos
- Analytical Chemistry - Center for Electrochemical Sciences (CES), Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Bright Nsolebna Jaato
- Technical Chemistry III, Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen Carl-Benz-Straße 199, 47057 Duisburg, Germany
| | - Ignacio Sanjuán
- Technical Chemistry III, Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen Carl-Benz-Straße 199, 47057 Duisburg, Germany
| | - Wolfgang Schuhmann
- Analytical Chemistry - Center for Electrochemical Sciences (CES), Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Corina Andronescu
- Technical Chemistry III, Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen Carl-Benz-Straße 199, 47057 Duisburg, Germany
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2
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Abstract
Mass-transport-limited catalysis and membrane transport can be characterized by concentration profiles surrounding active surfaces. Scanning electrochemical microscopy (SECM) is a tool that has been used to measure concentration profiles; however, the presence and geometry of the tip can distort these profiles due to hindered diffusion, which in turn alters chemical behavior at the catalytic surface. To fully characterize the behavior of surface features such as catalytic sites, it is essential to account for and analytically remove the effect of tip presence. In this work, atomic force microscopy-based SECM (AFM-SECM) measurements over poly(tetrafluoroethylene) (PTFE) and gold electrode surfaces are used to measure negative and positive-feedback approach curves, respectively. By inversely fitting these approach curves with a finite element method (FEM) model, we derive kinetic and geometric tip parameters that characterize the effect of tip presence. Tip effects may be removed in the model to estimate concentration profiles and reaction properties for the case where no tip is present. A maximum 120% increase in the concentration at one tip radii above the surface is observed due to the presence of the tip, where the concentration field is compressed vertically, in proportion to surface feature size and tip separation. Conical AFM-SECM tips, with a higher ratio of tip height to the base size, introduce less concentration distortion than disk-shaped AFM-SECM tips.
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Affiliation(s)
- Alex Mirabal
- Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, Michigan 48824, United States
| | - Scott Calabrese Barton
- Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, Michigan 48824, United States
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Limani N, Boudet A, Blanchard N, Jousselme B, Cornut R. Local probe investigation of electrocatalytic activity. Chem Sci 2020; 12:71-98. [PMID: 34163583 PMCID: PMC8178752 DOI: 10.1039/d0sc04319b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 11/04/2020] [Indexed: 11/21/2022] Open
Abstract
As the world energy crisis remains a long-term challenge, development and access to renewable energy sources are crucial for a sustainable modern society. Electrochemical energy conversion devices are a promising option for green energy supply, although the challenge associated with electrocatalysis have caused increasing complexity in the materials and systems, demanding further research and insights. In this field, scanning probe microscopy (SPM) represents a specific source of knowledge and understanding. Thus, our aim is to present recent findings on electrocatalysts for electrolysers and fuel cells, acquired mainly through scanning electrochemical microscopy (SECM) and other related scanning probe techniques. This review begins with an introduction to the principles of several SPM techniques and then proceeds to the research done on various energy-related reactions, by emphasizing the progress on non-noble electrocatalytic materials.
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Affiliation(s)
- N Limani
- Université Paris-Saclay, CEA, CNRS, NIMBE, LICSEN Gif-sur-Yvette 91191 France
| | - A Boudet
- Université Paris-Saclay, CEA, CNRS, NIMBE, LICSEN Gif-sur-Yvette 91191 France
| | - N Blanchard
- Université Paris-Saclay, CEA, CNRS, NIMBE, LICSEN Gif-sur-Yvette 91191 France
| | - B Jousselme
- Université Paris-Saclay, CEA, CNRS, NIMBE, LICSEN Gif-sur-Yvette 91191 France
| | - R Cornut
- Université Paris-Saclay, CEA, CNRS, NIMBE, LICSEN Gif-sur-Yvette 91191 France
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Polcari D, Dauphin-Ducharme P, Mauzeroll J. Scanning Electrochemical Microscopy: A Comprehensive Review of Experimental Parameters from 1989 to 2015. Chem Rev 2016; 116:13234-13278. [PMID: 27736057 DOI: 10.1021/acs.chemrev.6b00067] [Citation(s) in RCA: 213] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- David Polcari
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec Canada, H3A 0B8
| | - Philippe Dauphin-Ducharme
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec Canada, H3A 0B8
| | - Janine Mauzeroll
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec Canada, H3A 0B8
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5
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Sensing electroadsorption reactions and surface mobility of electroadsorbed species by scanning electrochemical induced desorption. J Electroanal Chem (Lausanne) 2016. [DOI: 10.1016/j.jelechem.2016.05.031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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6
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Yin YH, Niu L, Cao XL. Study on Electrocatalytic Activity of Platinum for Hydrogen Oxidation in Acidic Solution by Scanning Electrochemical Microscopy. J CHIN CHEM SOC-TAIP 2013. [DOI: 10.1002/jccs.200900158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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7
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Berger CEM, Datta HK, Horrocks BR. Simulation of generation-collection experiments with homogeneous kinetics: application to electrochemical investigation of superoxide radical anion generation by osteoclasts on bone. Phys Chem Chem Phys 2011; 13:5288-97. [PMID: 21279210 DOI: 10.1039/c0cp02350g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We report simulations of electrochemical generation-collection experiments in which the generator is a small disc producing a specified time-dependent flux of the analyte and the collector is a large planar electrode which collects the analyte at the mass transport-controlled rate. This geometry corresponds to many experiments in bioelectrochemistry where a relatively large sensor is used to detect the products of a cell's metabolism at low concentration. In particular, our simulations are motivated by attempts to understand our results on the detection of the superoxide radical anion burst generated by osteoclasts (bone-resorbing cells) in response to various stimuli. Superoxide is present at low levels and disproportionates in aqueous media; however, the homogeneous kinetics are included in our simulations and the results show that it is possible to estimate the magnitude of the flux of superoxide produced by the cells and to accurately determine the time-dependence of the flux in response to stimuli such as injection of parathyroid hormone, vitamin D(3) and pertussis toxin. In all these cases, the superoxide anion flux was successfully modeled as uniform across the cell surface with time-dependence of the form j(0)e(-k(d)t) + j(∞). j(∞) is the sustained flux of superoxide and the first-order rate constant k(d) and the magnitude j(0) describe the transient component of the flux. The simulations indicate that for cell-electrode gaps D approximately < √(D/k(d)), where D is the diffusion coefficient, the value of k(d) can be accurately extracted from the time-dependence of the collector current without detailed knowledge of parameters which are hard to measure during the experiment, e.g., the cell radius a and cell-electrode separation d. In the case of parathyroid hormone, the first-order rate constant describing the decay of the transient component was k(d) = 1.8 ± 0.8 × 10(-1) s(-1), but much slower decays were observed in response to pertussis toxin (k(d) = 1.5 ± 0.5 × 10(-2) s(-1)) and vitamin D(3) (k(d) = 1.1 ± 0.5 × 10(-3) s(-1)).
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Affiliation(s)
- C E M Berger
- Musculoskeletal Research Group, Institute of Cellular Medicine, Medical School, Framlington Place, Newcastle University, NE2 4HH, UK
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8
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Keddam M, Portail N, Trinh D, Vivier V. Progress in Scanning Electrochemical Microscopy by Coupling with Electrochemical Impedance and Quartz Crystal Microbalance. Chemphyschem 2009; 10:3175-82. [DOI: 10.1002/cphc.200900506] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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9
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Eckhard K, Chen X, Turcu F, Schuhmann W. Redox competition mode of scanning electrochemical microscopy (RC-SECM) for visualisation of local catalytic activity. Phys Chem Chem Phys 2009; 8:5359-65. [PMID: 19810414 DOI: 10.1039/b609511a] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In order to locally analyse catalytic activity on modified surfaces a transient redox competition mode of scanning electrochemical microscopy (SECM) has been developed. In a bi-potentiostatic experiment the SECM tip competes with the sample for the very same analyte. This leads to a current decrease at the SECM tip, if it is positioned in close proximity to an active catalyst site on the surface. Specifically, local catalytic activity of a Pt-catalyst modified sample with respect to the catalytic reduction of molecular oxygen was investigated. At higher local catalytic activity the local 02 partial pressure within the gap between accurately positioned SECM tip and sample is depleted, leading to a noticeable tip current decrease over active sites. A flexible software module has been implemented into the SECM to adapt the competition conditions by proper definition of tip and sample potentials. A potential pulse profile enables the localised electrochemically induced generation of molecular oxygen prior to the competition detection. The current decay curves are recorded over the entire duration of the applied reduction pulse. Hence, a time resolved processing of the acquired current values provides movies of the local oxygen concentration against x,y-position. The SECM redox competition mode was verified with a macroscopic Pt-disk electrode as a test sample to demonstrate the feasibility of the approach. Moreover, highly dispersed electro-deposited spots of gold and platinum on glassy carbon were visualised using the redox competition mode of SECM. Catalyst spots of different nature as well as activity inhomogeneities within one spot caused by local variations in Pt-loading were visualised successfully.
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Affiliation(s)
- Kathrin Eckhard
- Anal. Chem.-Elektroanalytik & Sensorik, Ruhr-Universität Bochum, Bochum, Germany
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10
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Pust SE, Maier W, Wittstock G. Investigation of Localized Catalytic and Electrocatalytic Processes and Corrosion Reactions with Scanning Electrochemical Microscopy (SECM). ACTA ACUST UNITED AC 2009. [DOI: 10.1524/zpch.2008.5426] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
AbstractScanning electrochemical microscopy (SECM) has developed into a very versatile tool for the investigation of solid-liquid, liquid-liquid and liquid-gas interfaces. The arrangement of an ultramicroelectrode (UME) in close proximity to the interface under study allows the application of a large variety of different experimental schemes. The most important have been named feedback mode, generation-collection mode, redox competition mode and direct mode. Quantitative descriptions are available for the UME signal, depending on different sample properties and experimental variables. Therefore, SECM has been established as an indispensible tool in many areas of fundamental electrochemical research. Currently, it also spreads as an important new method to solve more applied problems, in which inhomogeneous current distributions are typically observed on different length scales. Prominent examples include devices for electrochemical energy conversion such as fuel cells and batteries as well as localized corrosion phenomena. However, the direct local investigation of such systems is often impossible. Instead, suitable reaction schemes, sample environments, model samples and even new operation modes have to be introduced in order to obtain results that are relevant to the practical application. This review outlines and compares the theoretical basis of the different SECM working modes and reviews the application in the area of electrochemical energy conversion and localized corrosion with a special emphasis on the problems encountered when working with practical samples.
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11
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Burchardt M, Träuble M, Wittstock G. Digital Simulation of Scanning Electrochemical Microscopy Approach Curves to Enzyme Films with Michaelis−Menten Kinetics. Anal Chem 2009; 81:4857-63. [DOI: 10.1021/ac9004919] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Malte Burchardt
- Carl von Ossietzky University of Oldenburg, Faculty of Mathematics and Natural Sciences, Center of Interface Science, Institute of Pure and Applied Chemistry, D-26111 Oldenburg, Germany
| | - Markus Träuble
- Carl von Ossietzky University of Oldenburg, Faculty of Mathematics and Natural Sciences, Center of Interface Science, Institute of Pure and Applied Chemistry, D-26111 Oldenburg, Germany
| | - Gunther Wittstock
- Carl von Ossietzky University of Oldenburg, Faculty of Mathematics and Natural Sciences, Center of Interface Science, Institute of Pure and Applied Chemistry, D-26111 Oldenburg, Germany
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12
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A mechanistic investigation of di-tert-butyl nitroxide using scanning electrochemical microscopy (SECM). Electrochim Acta 2008. [DOI: 10.1016/j.electacta.2008.06.039] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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13
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Minguzzi A, Alpuche-Aviles MA, Rodríguez López J, Rondinini S, Bard AJ. Screening of oxygen evolution electrocatalysts by scanning electrochemical microscopy using a shielded tip approach. Anal Chem 2008; 80:4055-64. [PMID: 18447323 DOI: 10.1021/ac8001287] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxygen evolution electrocatalysts in acidic media were studied by scanning electrochemical microscopy (SECM) in the substrate generation-tip collection (SG-TC) imaging mode with a 100 microm diam tip. Pure IrO2 and Sn(1-x)Ir(x)O2 combinatorial mixtures were prepared by a sol-gel route to form arrays of electrocatalyst spots. The experimental setup has been developed to optimize screening of electrocatalyst libraries under conditions where the entire array is capable of the oxygen evolution reaction (OER). The activity of individual spots was determined by reducing the interference from the reaction products of neighboring spots diffusing to the tip over the spot of interest. A gold layer deposited on the external wall of the SECM tip was used as a tip shield. In this study the shield was kept at a constant potential to reduce oxygen under mass transfer controlled conditions. The tip shield consumes oxygen coming from the neighbor spots in the array and enables the tip to correctly detect the activity of the spot below the tip. Simulations and experimental results are shown, demonstrating the effectiveness of the tip shield with the SG-TC setup in determining the properties of the composite materials and imaging arrays.
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Affiliation(s)
- Alessandro Minguzzi
- Department of Physical-Chemistry and Electrochemistry, University of Milan, via Golgi 19, 20133 Milan, Italy
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14
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Methanol Tolerance of Pd–Co Oxygen Reduction Reaction Electrocatalysts Using Scanning Electrochemical Microscopy. ACTA ACUST UNITED AC 2008. [DOI: 10.1149/1.2931020] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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15
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Amemiya S, Bard AJ, Fan FRF, Mirkin MV, Unwin PR. Scanning electrochemical microscopy. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2008; 1:95-131. [PMID: 20636076 DOI: 10.1146/annurev.anchem.1.031207.112938] [Citation(s) in RCA: 272] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
This review describes work done in scanning electrochemical microscopy (SECM) since 2000 with an emphasis on new applications and important trends, such as nanometer-sized tips. SECM has been adapted to investigate charge transport across liquid/liquid interfaces and to probe charge transport in thin films and membranes. It has been used in biological systems like single cells to study ion transport in channels, as well as cellular and enzyme activity. It is also a powerful and useful tool for the evaluation of the electrocatalytic activities of different materials for useful reactions, such as oxygen reduction and hydrogen oxidation. SECM has also been used as an electrochemical tool for studies of the local properties and reactivity of a wide variety of materials, including metals, insulators, and semiconductors. Finally, SECM has been combined with several other nonelectrochemical techniques, such as atomic force microscopy, to enhance and complement the information available from SECM alone.
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Affiliation(s)
- Shigeru Amemiya
- University of Pittsburgh, Department of Chemistry, Pennsylvania 15260, USA
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Lu X, Wang Q, Liu X. Review: Recent applications of scanning electrochemical microscopy to the study of charge transfer kinetics. Anal Chim Acta 2007; 601:10-25. [PMID: 17904468 DOI: 10.1016/j.aca.2007.08.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2007] [Revised: 08/09/2007] [Accepted: 08/12/2007] [Indexed: 10/22/2022]
Abstract
Scanning electrochemical microscopy (SECM) has been proven to be a valuable technique for the quantitative investigation and surface analysis of a wide range of processes that occur at interfaces. In particular, there is a great deal of interest in studying the kinetics of charge transfer characteristics at the solid/liquid and liquid/liquid interface. This overview outlines recent advances and applications of SECM to the investigation of charge transfer reactions at the solid/liquid interface and liquid/liquid interface.
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Affiliation(s)
- Xiaoquan Lu
- College of Chemistry and Chemical Engineer, Northwest Normal University, Lanzhou, 730070, PR China
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17
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Wittstock G, Burchardt M, Pust SE, Shen Y, Zhao C. Scanning electrochemical microscopy for direct imaging of reaction rates. Angew Chem Int Ed Engl 2007; 46:1584-617. [PMID: 17285666 DOI: 10.1002/anie.200602750] [Citation(s) in RCA: 313] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Not only in electrochemistry but also in biology and in membrane transport, localized processes at solid-liquid or liquid-liquid interfaces play an important role at defect sites, pores, or individual cells, but are difficult to characterize by integral investigation. Scanning electrochemical microscopy is suitable for such investigations. After two decades of development, this method is based on a solid theoretical foundation and a large number of demonstrated applications. It offers the possibility of directly imaging heterogeneous reaction rates and locally modifying substrates by electrochemically generated reagents. The applications range from classical electrochemical problems, such as the investigation of localized corrosion and electrocatalytic reactions in fuel cells, sensor surfaces, biochips, and microstructured analysis systems, to mass transport through synthetic membranes, skin and tissue, as well as intercellular communication processes. Moreover, processes can be studied that occur at liquid surfaces and liquid-liquid interfaces.
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Affiliation(s)
- Gunther Wittstock
- Carl von Ossietzky Universität Oldenburg, Institut für Reine und Angewandte Chemie und Institut für Chemie und Biologie des Meeres, 26111 Oldenburg, Germany.
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Ghilane J, Guilloux-Viry M, Lagrost C, Simonet J, Hapiot P. Reactivity of Platinum Metal with Organic Radical Anions from Metal to Negative Oxidation States. J Am Chem Soc 2007; 129:6654-61. [PMID: 17461588 DOI: 10.1021/ja071483a] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The reaction of platinum metal with an organic molecular radical anion leads to the formation of iono-metallic phases where Pt exists under negative oxidation states. This puzzling transformation of a "noncorrodible metal" was examined using localized electrochemical techniques in dimethylformamide containing different tetra-alkylammonium salts chosen as test systems. Our experiments demonstrate that the platinum metal is locally reduced as soon as the Pt faces relatively moderate reducing conditions, for example, when the Pt is used as a negative electrode or when the metal is in the presence of a reducing agent such as an organic radical anion. Scanning electrochemical microscopy (SECM) analysis, current-distance curves, and transient mode responses provide detailed descriptions of the reactivity of Pt to form negative oxidation states (the key step is the reaction of the metal with a molecular reducing agent), of the insulating nature of the "reduced" solid phases of the thermodynamics and kinetics conditions of the Pt conversion. The passage from the conductor to insulator states controlled the spatial development of the reaction that always remains in competition with the other "natural" roles of a metallic electrode. Formally, the phenomena can be treated by analogy with the C. Amatore's model previously developed for the mediated reduction of the poly(tetrafluoroethylene). Consequences of this general reactivity of Pt are discussed in view of a wide utilization of this metal in reductive conditions and the possible applications of such processes in the micropatterning of metallic surfaces.
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Affiliation(s)
- Jalal Ghilane
- Sciences Chimiques de Rennes, UMR No. 6226 CNRS-Université de Rennes 1, Campus de Beaulieu, 35042 Rennes, France
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Wittstock G, Burchardt M, Pust S, Shen Y, Zhao C. Elektrochemische Rastermikroskopie zur direkten Abbildung von Reaktionsgeschwindigkeiten. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200602750] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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20
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Carano M, Bond AM. Prospects for the Application of Scanning Electrochemical Microscopy in Ionic Liquids. Aust J Chem 2007. [DOI: 10.1071/ch06269] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Prospects have been assessed for the application of the technique of scanning electrochemical microscopy (SECM) in viscous ionic liquids. Use of the Fc0/+ redox couple (Fc = ferrocene) to obtain microelectrode approach curves revealed that the required steady state behaviour needed for analysis of data relevant to conducting platinum and insulating glass substrates is moderately easy to achieve in a 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ionic liquid. However, in the more highly viscous 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid, where significantly lower diffusion coefficients are encountered, approach-curve data that conform to steady state theory are only found with very small microelectrodes (e.g., ≤2 μm diameter), very slow electrode–substrate approach rates (e.g., ≤0.05 μm s–1), and long equilibration times (e.g., 50 s). A comparison is provided with SECM approach curves acquired in aqueous media. SECM images of an Ag substrate in contact with [BMIM][BF4] also are presented and are of only slightly inferior quality to images obtained in water.
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Fernández JL, Hurth C, Bard AJ. Scanning Electrochemical Microscopy #54. Application To The Study Of Heterogeneous Catalytic ReactionsHydrogen Peroxide Decomposition. J Phys Chem B 2005; 109:9532-9. [PMID: 16852147 DOI: 10.1021/jp050340c] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A scanning electrochemical microscopy (SECM) approach for the analysis of heterogeneous catalytic reactions at solid-liquid interfaces is described and applied. In this scheme, reactant, generated at a tip, undergoes a reaction (e.g., disproportionation) at the substrate. The theoretical background for this study, performed by digital simulations using a finite difference method, considers a chemical reaction at the substrate with general stoichiometry. In this case, the fraction of regenerated mediator (nu(S)) may differ with respect to a substrate reaction that is the reverse of the tip reaction, resulting in an asymmetric mediator loop. Simulated tip current transients and approach curves at different values of the kinetic rate constant for reactions where nu(S) < 1 were used to analyze this new SECM situation. This approach was used to study the catalytic decomposition of hydrogen peroxide (HO2- --> 1/2O2 + OH-), where nu(S) = 0.5, on supported catalysts. A gold-mercury amalgam tip was used to quantitatively reduce dissolved O2 (mediator) to HO2-, which was decomposed back to oxygen at the catalyst substrate. Rate constants for the decomposition reaction on immobilized catalase and Pt particles were measured at different pH values by the correlation of experimental approach curves with the theoretical dependencies.
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Affiliation(s)
- José L Fernández
- Department of Chemistry and Biochemistry, Center for Nano and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712, USA
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22
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A preliminary study on chemical micro-machining of complex three-dimensional patterns on silicon substrates. J Solid State Electrochem 2005. [DOI: 10.1007/s10008-004-0636-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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23
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Fernández JL, Walsh DA, Bard AJ. Thermodynamic Guidelines for the Design of Bimetallic Catalysts for Oxygen Electroreduction and Rapid Screening by Scanning Electrochemical Microscopy. M−Co (M: Pd, Ag, Au). J Am Chem Soc 2005; 127:357-65. [PMID: 15631486 DOI: 10.1021/ja0449729] [Citation(s) in RCA: 540] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We propose guidelines for the design of improved bimetallic (and related) electrocatalysts for the oxygen reduction reaction (ORR) in acidic media. This guide is based on simple thermodynamic principles assuming a simple mechanism where one metal breaks the oxygen-oxygen bond of molecular O(2) and the other metal acts to reduce the resulting adsorbed atomic oxygen. Analysis of the Gibbs free energies of these two reactions guides the selection of combinations of metals that can produce alloy surfaces with enhanced activity for the ORR when compared to the constituent metals. Selected systems have been tested by fabricating arrays of metallic catalysts consisting of various binary and ternary combinations of Pd, Au, Ag, and Co deposited on glassy carbon (GC) substrates. The electrocatalytic activity of these materials for the ORR in acidic medium was examined using scanning electrochemical microscopy (SECM) in a new rapid-imaging mode. This was used to rapidly screen arrays covering a wide range of catalyst compositions for their activity for the ORR in 0.5 M H(2)SO(4). Using the SECM technique, we have identified combinations of metals with enhanced electrocatalytic activities when compared with the constituent, pure metals. Addition of Co to Pd, Au, and Ag clearly decreases the ORR overpotential, in agreement with the proposed model. Catalyst spots that exhibited enhanced electrocatalytic activity in the SECM screening technique were then examined using classical rotating disk electrode (RDE) experiments. The activity of carbon black supported catalyst mixtures on a GC RDE and the electrocatalytic activity determined using the SECM screening technique showed excellent agreement. C/Pd-Co electrodes (10-30% Co) exhibited remarkable activity for ORR catalysis, close to that of carbon-supported Pt.
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Affiliation(s)
- José L Fernández
- Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA
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Fernández JL, Mano N, Heller A, Bard AJ. Optimization Of “Wired” Enzyme O2-Electroreduction Catalyst Compositions by Scanning Electrochemical Microscopy. Angew Chem Int Ed Engl 2004; 43:6355-7. [PMID: 15558668 DOI: 10.1002/anie.200461528] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- José L Fernández
- Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712, USA
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25
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Fernández JL, Mano N, Heller A, Bard AJ. Optimization Of “Wired” Enzyme O2-Electroreduction Catalyst Compositions by Scanning Electrochemical Microscopy. Angew Chem Int Ed Engl 2004. [DOI: 10.1002/ange.200461528] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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