Special Issue "Electrochemical Surface Science: Basics and Applications"

A special issue of Surfaces (ISSN 2571-9637).

Deadline for manuscript submissions: closed (20 February 2019)

Special Issue Editors

Guest Editor
Prof. Dr. Gaetano Granozzi

Universita degli Studi di Padova, Italy
Website | E-Mail
Phone: 00393347151920
Interests: ultrathin films, 2D materials, model electrocatalysts, model catalysts, HER, ORR and CRR
Guest Editor
Prof. Dr. Nicolas Alonso-Vante

IC2MP-UMR CNRS 7285, University of Poitiers, 86022 Poitiers, France
Website | E-Mail
Interests: electrochemistry; photoelectrochemistry; ORR-, HER-, OER-electrocatalysis; energy and fuels; nanomaterials; micro-fuel cells

Special Issue Information

Dear Colleagues,

Electrochemical surface science (EC-SS) is the natural advancement of traditional surface science (where gas-vacuum/solid interfaces are studied) to liquid(solution)/electrified solid interfaces. Such a merging between two different disciplines, i.e., surface science (SS) and electrochemistry, has been officially advanced ca. three decades ago. The main peculiarity of EC-SS versus electrochemistry is the reductionist approach, inherited from SS, aiming at understanding at atomic level the microscopic processes occurring at electrodes. Few exemplar keystones tools of EC-SS are EC-scanning probe microscopies, operando and in-situ spectroscopies and electron microscopies, differential EC mass spectrometry (DEMS), etc.

Nowadays, the number of established SS research groups converted into EC-SS is not yet huge, also because the number of SS groups is itself rather limited.  However, EC-SS is indirectly (and often unconsciously) receiving a great impulse from the need for a rational design of energy conversion and storage devices for next generation energetic landscape. As a matter of fact, the number of material science groups deeply involved in such a challenging field has tremendously expanded, and, within such a panorama, EC and SS investigations are intimately combined in a huge number of papers. 

The aim of this Special Issue is to offer an open-access forum where researchers in the field of electrochemistry, surface science and materials science can underline the great advances that can be reached by exploiting the EC-SS approach. In this Special Issue, papers addressing both basic science and more applied issues in the field EC-SS and energy conversion and storage materials are very welcome.

Prof. Dr. Gaetano Granozzi
Prof. Dr. Nicolas Alonso-Vante
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Surfaces is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) is waived for well-prepared manuscripts submitted to this issue. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Advanced tools for electrochemical surface science approach
  • In-situ and operando techniques
  • Structural and chemical surface characterization of electrodes’ surfaces
  • Materials for electrochemical energy conversion and storage
  • Model and Real world electrocatalysts and photoelectrocatalysts
  • Computational studies and modeling

Published Papers (27 papers)

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Research

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Open AccessArticle
Investigation of Photoelectron Properties of Polymer Films with Silicon Nanoparticles
Surfaces 2019, 2(2), 387-394; https://doi.org/10.3390/surfaces2020028
Received: 21 February 2019 / Revised: 4 May 2019 / Accepted: 11 May 2019 / Published: 13 May 2019
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Abstract
Hybrid samples consisting of polymer poly-3(hexylthiophene) (P3HT) and silicon nanoparticles were prepared. It was found that the obtained samples were polymer matrixes with conglomerates of silicon nanoparticles of different sizes (10–104 nm). It was found that, under illumination, the process of nonequilibrium [...] Read more.
Hybrid samples consisting of polymer poly-3(hexylthiophene) (P3HT) and silicon nanoparticles were prepared. It was found that the obtained samples were polymer matrixes with conglomerates of silicon nanoparticles of different sizes (10–104 nm). It was found that, under illumination, the process of nonequilibrium charge carrier separation between the silicon nanoparticles and P3HT with subsequent localization of the hole in the polymer can be successfully detected using electron paramagnetic resonance (EPR) spectroscopy. It was established that the main type of paramagnetic centers in P3HT/silicon nanoparticles are positive polarons in P3HT. For comparison, samples consisting only of polymer and silicon nanoparticles were also investigated by the EPR technique. The polarons in the P3HT and Pb centers in the silicon nanoparticles were observed. The possibility of the conversion of solar energy into electric energy is shown using structures consisting of P3HT polymer and silicon nanoparticles prepared by different methods, including the electrochemical etching of a silicon single crystal in hydrofluoric acid solution and the laser ablation of single-crystal silicon in organic solvents. The results can be useful for solar cell development. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Formic Acid Oxidation on Pd Thin Film Coated Au Nanocrystals
Surfaces 2019, 2(2), 372-386; https://doi.org/10.3390/surfaces2020027
Received: 5 April 2019 / Revised: 26 April 2019 / Accepted: 6 May 2019 / Published: 10 May 2019
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Abstract
Cubic, octahedral, and rhombic dodecahedral gold nanocrystals enclosed by {100}, {111}, and {110} facets, respectively, were prepared by a seed-mediated growth method at the room temperature. Palladium thin films were coated on these Au nanocrystals by a redox replacement approach to explore their [...] Read more.
Cubic, octahedral, and rhombic dodecahedral gold nanocrystals enclosed by {100}, {111}, and {110} facets, respectively, were prepared by a seed-mediated growth method at the room temperature. Palladium thin films were coated on these Au nanocrystals by a redox replacement approach to explore their catalytic activities. It is revealed that formic acid and carbon monoxide oxidation in 0.1 M HClO4 on Au nanocrystals coated with one monolayer (ML) of Pd are facet-dependent and resemble those obtained from corresponding Pd single crystals and Pd films deposited on bulk Au single crystals, suggesting epitaxial growth of Pd overlayers on the Au nanocrystal surfaces. As the Pd film thickness increased, formic acid oxidation current density decreased and the CO oxidation potential moved to more negative. The catalytic activity remained largely unchanged after 3–5 MLs of Pd deposition. The specific adsorption of (bi)sulfate was shown to hinder the formic acid oxidation and the effect decreased with the increasing Pd film thickness. These observations were explained in the framework of the d-band theory. This study highlights the feasibility of engineering high-performance catalysts through deposition of catalytically active metal thin films on facet-controlled inert nanocrystals. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Sputtered Platinum Thin-films for Oxygen Reduction in Gas Diffusion Electrodes: A Model System for Studies under Realistic Reaction Conditions
Surfaces 2019, 2(2), 336-348; https://doi.org/10.3390/surfaces2020025
Received: 20 March 2019 / Revised: 16 April 2019 / Accepted: 24 April 2019 / Published: 28 April 2019
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Abstract
The development of catalysts for the oxygen reduction reaction in low-temperature fuel cells depends on efficient and accurate electrochemical characterization methods. Currently, two primary techniques exist: rotating disk electrode (RDE) measurements in half-cells with liquid electrolyte and single cell tests with membrane electrode [...] Read more.
The development of catalysts for the oxygen reduction reaction in low-temperature fuel cells depends on efficient and accurate electrochemical characterization methods. Currently, two primary techniques exist: rotating disk electrode (RDE) measurements in half-cells with liquid electrolyte and single cell tests with membrane electrode assemblies (MEAs). While the RDE technique allows for rapid catalyst benchmarking, it is limited to electrode potentials far from operating fuel cells. On the other hand, MEAs can provide direct performance data at realistic conditions but require specialized equipment and large quantities of catalyst, making them less ideal for early-stage development. Using sputtered platinum thin-film electrodes, we show that gas diffusion electrode (GDE) half-cells can be used as an intermediate platform for rapid benchmarking at fuel-cell relevant current densities (~1 A cm−2). Furthermore, we demonstrate how different parameters (loading, electrolyte concentration, humidification, and Nafion membrane) influence the performance of unsupported platinum catalysts. The specific activity could be measured independent of the applied loading at potentials down to 0.80 VRHE reaching a value of 0.72 mA cm−2 at 0.9 VRHE in the GDE. By comparison with RDE measurements and Pt/C measurements, we establish the importance of catalyst characterization under realistic reaction conditions. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Electro-Oxidation of CO Saturated in 0.1 M HClO4 on Basal and Stepped Pt Single-Crystal Electrodes at Room Temperature Accompanied by Surface Reconstruction
Surfaces 2019, 2(2), 315-325; https://doi.org/10.3390/surfaces2020023
Received: 28 December 2018 / Revised: 6 April 2019 / Accepted: 11 April 2019 / Published: 16 April 2019
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Abstract
The electro-oxidation of CO on Pt surface is not only fundamentally important in electrochemistry, but also practically important in residential fuel cells for avoiding the poisoning of Pt catalysts by CO. We carried out cyclic voltammetry on Pt(111), (110), (100), (10 10 9), [...] Read more.
The electro-oxidation of CO on Pt surface is not only fundamentally important in electrochemistry, but also practically important in residential fuel cells for avoiding the poisoning of Pt catalysts by CO. We carried out cyclic voltammetry on Pt(111), (110), (100), (10 10 9), (10 9 8), (10 2 1), (432), and (431) single-crystal surfaces using a three compartment cell to understand the activity and durability towards the electro-oxidation of CO saturated in 0.1 M HClO4. During the potential cycles between 0.07 and 0.95 V vs. the reversible hydrogen electrode, the current for the electro-oxidation of CO at potentials lower than 0.5 V disappeared, accompanied by surface reconstruction. Among the electrodes, the Pt(100) electrode showed the lowest onset potential of 0.29 V, but the activity abruptly disappeared after one potential cycle; the active sites were extremely unstable. In order to investigate the processes of the deactivation, potential-step measurements were also conducted on Pt(111) in a CO-saturated solution. Repeated cycles of the formations of Pt oxides at a high potential and Pt carbonyl species at a low potential on the surface were proposed as the deactivation process. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Spatially Resolved XPS Characterization of Electrochemical Surfaces
Surfaces 2019, 2(2), 295-314; https://doi.org/10.3390/surfaces2020022
Received: 20 February 2019 / Revised: 5 April 2019 / Accepted: 9 April 2019 / Published: 15 April 2019
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Abstract
Synchrotron-based scanning photoelectron microscopy (SPEM) has opened unique opportunities for exploiting processes occurring at surfaces and interfaces, which control the properties of materials for electrochemical devices, where issues of chemical and morphological complexity at microscopic length scales should be faced and understood. The [...] Read more.
Synchrotron-based scanning photoelectron microscopy (SPEM) has opened unique opportunities for exploiting processes occurring at surfaces and interfaces, which control the properties of materials for electrochemical devices, where issues of chemical and morphological complexity at microscopic length scales should be faced and understood. The present article aims to demonstrate the present capabilities of SPEM to explore the surface composition of micro- and nano-structured materials, focusing on cases relevant to electrochemical technologies. We report and discuss a selection of recent results about three different systems, targeting hot topics in the fields of electrochemical energy storage and electrochemical fabrication: (i) an in-depth analysis of Ag-In electrodeposited alloys exhibiting dynamic pattern formation, (ii) the analysis of electrochemical processes at the electrodes of a self-driven solid oxide fuel cell and (iii) an operando characterization of a single-chamber solid oxide fuel cell. The last example has been performed at near-ambient pressure conditions using a unique specially designed setup which extends the traditional capabilities of scanning photoemission microscopes in the ultra-high and high-vacuum regimes to operating conditions that are closer to realistic ones, contributing to overcome the so-called “pressure gap”. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Probing the Surface of Noble Metals Electrochemically by Underpotential Deposition of Transition Metals
Surfaces 2019, 2(2), 257-276; https://doi.org/10.3390/surfaces2020020
Received: 15 February 2019 / Revised: 29 March 2019 / Accepted: 2 April 2019 / Published: 9 April 2019
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Abstract
The advances in material science have led to the development of novel and various materials as nanoparticles or thin films. Underpotential deposition (upd) of transition metals appears to be a very sensitive method for probing the surfaces of noble metals, which [...] Read more.
The advances in material science have led to the development of novel and various materials as nanoparticles or thin films. Underpotential deposition (upd) of transition metals appears to be a very sensitive method for probing the surfaces of noble metals, which is a parameter that has an important effect on the activity in heterogeneous catalysis. Underpotential deposition as a surface characterization tool permits researchers to precisely determine the crystallographic orientations of nanoparticles or the real surface area of various surfaces. Among all the work dealing with upd, this review focuses specifically on the main upd systems used to probe surfaces of noble metals in electrocatalysis, from poly‒ and single-crystalline surfaces to nanoparticles. Cuupd is reported as a tool to determine the active surface area of gold‒ and platinum‒based bimetallic electrode materials. Pbupd is the most used system to assess the crystallographic orientations on nanoparticles’ surface. In the case of platinum, Bi and Ge adsorptions are singled out for probing (1 1 1) and (1 0 0) facets, respectively. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Nitrogen-Doped Ordered Mesoporous Carbons Supported Co3O4 Composite as a Bifunctional Oxygen Electrode Catalyst
Surfaces 2019, 2(2), 229-240; https://doi.org/10.3390/surfaces2020018
Received: 20 February 2019 / Revised: 25 March 2019 / Accepted: 26 March 2019 / Published: 29 March 2019
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Abstract
It is increasingly useful to develop bifunctional catalysts for oxygen reduction and oxygen evolution reaction (ORR and OER) for fuel cells, metal-air rechargeable batteries, and unitized regenerative cells. Here, based on the excellent conductivity and stability of ordered mesoporous carbons, and the best [...] Read more.
It is increasingly useful to develop bifunctional catalysts for oxygen reduction and oxygen evolution reaction (ORR and OER) for fuel cells, metal-air rechargeable batteries, and unitized regenerative cells. Here, based on the excellent conductivity and stability of ordered mesoporous carbons, and the best ORR and OER activity of Co3O4, the composite Co3O4/N-HNMK-3 was designed and manufactured by means of a solvothermal method, using ordered N-doped mesoporous carbon (N-HNMK-3) as substrate, and then the bifunctional electrocatalytic performance corresponding to ORR, OER in alkaline media was carefully investigated. The results showed that Co3O4/N-HNMK-3 composite, a non-precious metal centered electrocatalyst, displayed excellent ORR performance (activity, selectivity, and stability) close to that of commercial 20 wt.% Pt/C and a promising OER activity near 20 wt.% RuO2/C. The outstanding bifunctional activities of Co3O4/N-HNMK-3 was assessed with the lowest △E value of 0.86 V (EOER,10 mA cm−2-EORR,−3 mA cm−2) with respect to the two commercial precious metal-based electrocatalysts. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
An Electrochemical Route for Hot Alkaline Blackening of Steel: A Nitrite Free Approach
Surfaces 2019, 2(2), 216-228; https://doi.org/10.3390/surfaces2020017
Received: 23 February 2019 / Revised: 23 March 2019 / Accepted: 26 March 2019 / Published: 29 March 2019
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Abstract
Blackening belongs to the predominant technological processes in preserving steel surfaces from corrosion by generating a protective magnetite overlayer. In place of the commonly used dipping-procedure into nitrite-containing blackening baths at boiling temperatures that are far above 100 °C, here we describe a [...] Read more.
Blackening belongs to the predominant technological processes in preserving steel surfaces from corrosion by generating a protective magnetite overlayer. In place of the commonly used dipping-procedure into nitrite-containing blackening baths at boiling temperatures that are far above 100 °C, here we describe a more environmentally friendly electrochemical route that operates at temperatures, even below 100 °C. After an investigation of the electrochemical behavior of steel samples in alkaline solutions at various temperatures, the customarily required bath temperature of more than 130 °C could be significantly lowered to about 80 °C by applying a DC voltage that leads to an electrode potential of 0.5−0.6 V vs. Pt. Thus, it was possible to eliminate the use of hazardous sodium nitrite economically and in an optimum way. Electrochemical quantification of the corrosion behavior of steel surfaces that were in contact with 0.1 M KCl solution was carried out by linear sweep voltammetry and by Tafel slope analysis. When comparing these data, even the corrosion rates of conventional blackened surfaces are of the same magnitude as a blank steel surface. This proves that magnetite overlayers represent rather poor protective layers in the absence of additional sealing. Moreover, cyclic voltammetry (CV), atomic force microscopy (AFM), scanning electron microscopy (SEM) and auger electron spectroscopy (AES) characterized the electrochemically blackened steel surfaces. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Cyclic Voltammetry Characterization of Au, Pd, and AuPd Nanoparticles Supported on Different Carbon Nanofibers
Surfaces 2019, 2(1), 205-215; https://doi.org/10.3390/surfaces2010016
Received: 18 January 2019 / Revised: 28 February 2019 / Accepted: 13 March 2019 / Published: 19 March 2019
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Abstract
Three types of carbon nanofibers (pyrolytically stripped carbon nanofibers (PS), low-temperature heat treated carbon nanofibers (LHT), and high-temperature heat treated carbon nanofibers (HHT)) with different graphitization degrees and surface chemistry have been used as support for Au, Pd, or bimetallic AuPd alloy nanoparticles [...] Read more.
Three types of carbon nanofibers (pyrolytically stripped carbon nanofibers (PS), low-temperature heat treated carbon nanofibers (LHT), and high-temperature heat treated carbon nanofibers (HHT)) with different graphitization degrees and surface chemistry have been used as support for Au, Pd, or bimetallic AuPd alloy nanoparticles (NPs). The carbon supports have been characterized using Raman, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). Moreover, the morphology of the metal nanoparticles was investigated using transmission electron microscopy (TEM) and CV. The different properties of the carbon-based supports (particularly the graphitization degree) yield different electrochemical behaviors, in terms of potential window widths and electrocatalytic effects. Comparing the electrochemical behavior of monometallic Au and Pd and bimetallic AuPd, it is possible to observe the interaction of the two metals when alloyed. Moreover, we demonstrate that carbon surface has a strong effect on the electrochemical stability of AuPd nanoparticles. By tuning the Au-Pd nanoparticles’ morphology and modulating the surface chemistry of the carbon support, it is possible to obtain materials characterized by novel electrochemical properties. This aspect makes them good candidates to be conveniently applied in different fields. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
“Click” Chemistry on Gold Electrodes Modified with Reduced Graphene Oxide by Electrophoretic Deposition
Surfaces 2019, 2(1), 193-204; https://doi.org/10.3390/surfaces2010015
Received: 22 January 2019 / Revised: 6 March 2019 / Accepted: 8 March 2019 / Published: 18 March 2019
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Abstract
The coating of electrical interfaces with reduced graphene oxide (rGO) films and their subsequent chemical modification are essential steps in the fabrication of graphene-based sensing platforms. In this work, electrophoretic deposition (EPD) of graphene oxide at 2.5 V for 300 s followed by [...] Read more.
The coating of electrical interfaces with reduced graphene oxide (rGO) films and their subsequent chemical modification are essential steps in the fabrication of graphene-based sensing platforms. In this work, electrophoretic deposition (EPD) of graphene oxide at 2.5 V for 300 s followed by vapor treatment were employed to coat gold electrodes uniformly with rGO. These interfaces showed excellent electron transfer characteristics for redox mediators such as ferrocene methanol and potassium ferrocyanide. Functional groups were integrated onto the Au/rGO electrodes by the electro-reduction of an aryldiazonium salt, 4-((triisopropylsilyl)ethylenyl)benzenediazonium tetrafluoroborate (TIPS-Eth-ArN) in our case. Chemical deprotection of the triisopropylsilyl function resulted in propargyl-terminated Au/rGO electrodes to which azidomethylferrocene was chemically linked using the Cu(I) catalyzed “click” chemistry. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Effects of the Interfacial Structure on the Methanol Oxidation on Platinum Single Crystal Electrodes
Surfaces 2019, 2(1), 177-192; https://doi.org/10.3390/surfaces2010014
Received: 11 February 2019 / Revised: 27 February 2019 / Accepted: 1 March 2019 / Published: 12 March 2019
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Abstract
Methanol oxidation has been studied on low index platinum single crystal electrodes using methanol solutions with different pH (1–5) in the absence of specific adsorption. The goal is to determine the role of the interfacial structure in the reaction. The comparison between the [...] Read more.
Methanol oxidation has been studied on low index platinum single crystal electrodes using methanol solutions with different pH (1–5) in the absence of specific adsorption. The goal is to determine the role of the interfacial structure in the reaction. The comparison between the voltammetric profiles obtained in the presence and absence of methanol indicates that methanol oxidation is only taking place when the surface is partially covered by adsorbed OH. Thus, on the Pt(111) electrode, the onset for the direct oxidation of methanol and the adsorption of OH coincide. In this case, the adsorbed OH species are not a mere spectator, because the obtained results for the reaction order for methanol and the proton concentrations indicate that OH adsorbed species are involved in the reaction mechanism. On the other hand, the dehydrogenation step to yield adsorbed CO on the Pt(100) surface coincides with the onset of OH adsorption on this electrode. It is proposed that adsorbed OH collaborates in the dehydrogenation step during methanol oxidation, facilitating either the adsorption of the methanol in the right configuration or the cleavage of the C—H bond. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Strategies to Hierarchical Porosity in Carbon Nanofiber Webs for Electrochemical Applications
Surfaces 2019, 2(1), 159-176; https://doi.org/10.3390/surfaces2010013
Received: 4 February 2019 / Revised: 22 February 2019 / Accepted: 25 February 2019 / Published: 5 March 2019
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Abstract
Morphology and porosity are crucial aspects for designing electrodes with facile transport of electrons, ions and matter, which is a key parameter for electrochemical energy storage and conversion. Carbon nanofibers (CNFs) prepared by electrospinning are attractive for their high aspect ratio, inter-fiber macroporosity [...] Read more.
Morphology and porosity are crucial aspects for designing electrodes with facile transport of electrons, ions and matter, which is a key parameter for electrochemical energy storage and conversion. Carbon nanofibers (CNFs) prepared by electrospinning are attractive for their high aspect ratio, inter-fiber macroporosity and their use as self-standing electrodes. The present work compares several strategies to induce intra-fiber micro-mesoporosity in self-standing CNF webs prepared by electrospinning polyacrylonitrile (PAN). Two main strategies were investigated, namely i) a templating method based on the addition of a porogen (polymethyl methacrylate, polyvinylpyrrolidone, Nafion® or ZnCl2) in the electrospinning solution of PAN, or ii) the activation in ammonia of previously formed CNF webs. The key result of this study is that open intra-fiber porosity could be achieved only when the strategies i) and ii) were combined. When each approach was applied separately, only closed intra-fiber porosity or no intra-fiber porosity was observed. In contrast, when both strategies were used in combination all CNF webs showed high mass-specific areas in the range of 325 to 1083 m2·g−1. Selected webs were also characterized for their carbon structure and electrical conductivity. The best compromise between high porosity and high electrical conductivity was identified as the fibrous web electrospun from PAN and polyvinylpyrrolidone. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Potential Dependent Structure and Stability of Cu(111) in Neutral Phosphate Electrolyte
Surfaces 2019, 2(1), 145-158; https://doi.org/10.3390/surfaces2010012
Received: 30 January 2019 / Revised: 19 February 2019 / Accepted: 20 February 2019 / Published: 24 February 2019
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Abstract
Copper and copper oxide electrode surfaces are suitable for the electrochemical reduction of CO2 and produce a range of products, with the product selectivity being strongly influenced by the surface structure of the copper electrode. In this paper, we present in-situ surface [...] Read more.
Copper and copper oxide electrode surfaces are suitable for the electrochemical reduction of CO2 and produce a range of products, with the product selectivity being strongly influenced by the surface structure of the copper electrode. In this paper, we present in-situ surface X-ray diffraction studies on Cu(111) electrodes in neutral phosphate buffered electrolyte solution. The underlying mechanism of the phosphate adsorption and deprotonation of the (di)-hydrogen phosphate is accompanied by a roughening of the copper surface. A change in morphology of the copper surface induced by a roughening process caused by the formation of a mixed copper–oxygen layer could also be observed. The stability of the Cu(111) surface and the change of morphology upon potential cycling strongly depends on the preparation method and history of the electrode. The presence of copper islands on the surface of the Cu(111) electrode leads to irreversible changes in surface morphology via a 3D Cu growth mechanism. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Interface Science Using Ambient Pressure Hard X-ray Photoelectron Spectroscopy
Surfaces 2019, 2(1), 78-99; https://doi.org/10.3390/surfaces2010008
Received: 18 December 2018 / Revised: 23 January 2019 / Accepted: 24 January 2019 / Published: 28 January 2019
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Abstract
The development of novel in situ/operando spectroscopic tools has provided the opportunity for a molecular level understanding of solid/liquid interfaces. Ambient pressure photoelectron spectroscopy using hard X-rays is an excellent interface characterization tool, due to its ability to interrogate simultaneously the chemical composition [...] Read more.
The development of novel in situ/operando spectroscopic tools has provided the opportunity for a molecular level understanding of solid/liquid interfaces. Ambient pressure photoelectron spectroscopy using hard X-rays is an excellent interface characterization tool, due to its ability to interrogate simultaneously the chemical composition and built-in electrical potentials, in situ. In this work, we briefly describe the “dip and pull” method, which is currently used as a way to investigate in situ solid/liquid interfaces. By simulating photoelectron intensities from a functionalized TiO2 surface buried by a nanometric-thin layer of water, we obtain the optimal photon energy range that provides the greatest sensitivity to the interface. We also study the evolution of the functionalized TiO2 surface chemical composition and correlated band-bending with a change in the electrolyte pH from 7 to 14. Our results provide general information about the optimal experimental conditions for characterizing the solid/liquid interface using the “dip and pull” method, and the unique possibilities offered by this technique. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Oxygen Reduction Reaction on Polycrystalline Platinum: On the Activity Enhancing Effect of Polyvinylidene Difluoride
Surfaces 2019, 2(1), 69-77; https://doi.org/10.3390/surfaces2010007
Received: 20 December 2018 / Revised: 18 January 2019 / Accepted: 21 January 2019 / Published: 24 January 2019
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Abstract
There have been several reports concerning the performance improving properties of additives, such as polyvinylidene difluoride (PVDF), to the membrane or electrocatalyst layer of proton exchange membrane fuel cells (PEMFC). However, it is not clear if the observed performance enhancement is due to [...] Read more.
There have been several reports concerning the performance improving properties of additives, such as polyvinylidene difluoride (PVDF), to the membrane or electrocatalyst layer of proton exchange membrane fuel cells (PEMFC). However, it is not clear if the observed performance enhancement is due to kinetic, mass transport, or anion blocking effects of the PVDF. In a previous investigation using a thin-film rotating disk electrode (RDE) approach (of decreased complexity as compared to membrane electrode assembly (MEA) tests), a performance increase for the oxygen reduction reaction (ORR) could be confirmed. However, even in RDE measurements, reactant mass transport in the catalyst layer cannot be neglected. Therefore, in the present study, the influence of PVDF is re-examined by coating polycrystalline bulk Pt electrodes by PVDF and measuring ORR activity. The results on polycrystalline bulk Pt indicate that the effects of PVDF on the reaction kinetics and anion adsorption are limited, and that the observed performance increase on high surface area Pt/C most likely is due to an erroneous estimation of the electrochemical active surface area (ECSA) from CO stripping and Hupd. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Surface Investigation on Electrochemically Deposited Lead on Gold
Surfaces 2019, 2(1), 56-68; https://doi.org/10.3390/surfaces2010006
Received: 17 December 2018 / Revised: 11 January 2019 / Accepted: 14 January 2019 / Published: 17 January 2019
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Abstract
Electrodeposition of Pb on Au has been of interest for the variety of surface phenomena such as the UnderPotential Deposition (UPD) and surface alloying. Here, we examined the interface between the electrodeposited Pb film on Au, using surface sensitive techniques such as X-ray [...] Read more.
Electrodeposition of Pb on Au has been of interest for the variety of surface phenomena such as the UnderPotential Deposition (UPD) and surface alloying. Here, we examined the interface between the electrodeposited Pb film on Au, using surface sensitive techniques such as X-ray Photoelectron Spectroscopy (XPS), Ultraviolet Photoelectron Spectroscopy (UPS), Energy-Filtered Photoemission Electron Microscopy (EF-PEEM) and Work Function (WF) mapping. The initially electrodeposited Pb overlayer (~4 ML equivalent thickness) was transferred from the electrochemical cell to the UHV system. The deposited Pb layer was subjected to Argon sputtering cycles to remove oxide formed due to air exposure and gradually thinned down to a monolayer level. Surface science acquisitions showed the existence of a mixed oxide/metallic Pb overlayer at the monolayer level that transformed to a metallic Pb upon high temperature annealing (380 °C for 1 h) and measured changes of the electronic interaction that can be explained by Pb/Au surface alloy formation. The results show the electronic interaction between metallic Pb and Au is different from the interaction of Au with the PbO and Pb/PbO mixed layer; the oxide interface is less strained so the surface stress driven mixing between Au is not favored. The work illustrates applications of highly surface sensitive methods in the characterization of the surface alloy systems that can be extended to other complex and ultrathin mixed-metallic systems (designed or spontaneously formed). Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Co3O4 Nanopetals on Si as Photoanodes for the Oxidation of Organics
Surfaces 2019, 2(1), 41-53; https://doi.org/10.3390/surfaces2010004
Received: 13 November 2018 / Revised: 8 January 2019 / Accepted: 9 January 2019 / Published: 11 January 2019
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Abstract
Cobalt oxide nanopetals were grown on silicon electrodes by heat-treating metallic cobalt films deposited by DC magnetron sputtering. We show that cobalt oxide, with this peculiar nanostructure, is active towards the photo-electrochemical oxidation of water as well as of organic molecules, and that [...] Read more.
Cobalt oxide nanopetals were grown on silicon electrodes by heat-treating metallic cobalt films deposited by DC magnetron sputtering. We show that cobalt oxide, with this peculiar nanostructure, is active towards the photo-electrochemical oxidation of water as well as of organic molecules, and that its electrochemical properties are directly linked to the structure of its surface. The formation of Co3O4 nanopetals, induced by oxidizing annealing at 300 °C, considerably improves the performance of the material with respect to simple cobalt oxide films. Photocurrent measurements and electrochemical impedance are used to explain the behavior of the different structures and to highlight their potential application in water remediation technologies. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
X-ray Absorption under Operating Conditions for Solid-Oxide Fuel Cells Electrocatalysts: The Case of LSCF/YSZ
Surfaces 2019, 2(1), 32-40; https://doi.org/10.3390/surfaces2010003
Received: 5 December 2018 / Revised: 19 December 2018 / Accepted: 2 January 2019 / Published: 8 January 2019
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Abstract
We describe a novel electrochemical cell for X-ray absorption spectroscopy (XAS) experiments during electrical polarization suitable for high-temperature materials such as those used in solid oxide fuel cells. A half-cell LSCF/YSZ was then investigated under cathodic and anodic conditions (850 °C and applied [...] Read more.
We describe a novel electrochemical cell for X-ray absorption spectroscopy (XAS) experiments during electrical polarization suitable for high-temperature materials such as those used in solid oxide fuel cells. A half-cell LSCF/YSZ was then investigated under cathodic and anodic conditions (850 °C and applied electrical bias ranging from +1 V to −1 V in air). The in situ XAS measurements allowed us to follow the LSCF degradation into simple oxides. The rapid deterioration of LSCF is ascribed to the formation of excess of oxygen vacancies leading to the collapse of the mixed perovskite structure. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Methanol Oxidation on Graphenic-Supported Platinum Catalysts
Surfaces 2019, 2(1), 16-31; https://doi.org/10.3390/surfaces2010002
Received: 19 November 2018 / Revised: 28 December 2018 / Accepted: 29 December 2018 / Published: 6 January 2019
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Abstract
Graphene oxide (GO), reduced graphene oxide by thermal treatment (rGO-TT), nitrogen-modified rGO (N-rGO), and carbon Vulcan were synthesized and employed in the current work as catalyst support for Pt nanoparticles, to study their properties and impact toward the methanol oxidation reaction (MOR) in [...] Read more.
Graphene oxide (GO), reduced graphene oxide by thermal treatment (rGO-TT), nitrogen-modified rGO (N-rGO), and carbon Vulcan were synthesized and employed in the current work as catalyst support for Pt nanoparticles, to study their properties and impact toward the methanol oxidation reaction (MOR) in sulfuric acid medium. Several physicochemical techniques, such as X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Raman, and elemental analysis were employed to characterize the novel materials, while potentiodynamic and potentiostatic methods were used to study catalytic performance toward the methanol oxidation reaction in acidic medium. The main results indicate a high influence of the support on the surface electronic state of the catalyst, and consequently the catalytic performance toward the MOR is modified. Accordingly, Pt/N-rGO and Pt/rGO-TT show the lowest and the highest catalytic performance toward the MOR, respectively. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Electrochemical Behavior of Pt–Ru Catalysts Supported on Graphitized Ordered Mesoporous Carbons toward CO and Methanol Oxidation
Surfaces 2019, 2(1), 1-15; https://doi.org/10.3390/surfaces2010001
Received: 29 November 2018 / Revised: 21 December 2018 / Accepted: 27 December 2018 / Published: 3 January 2019
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Abstract
In this work, graphitized ordered mesoporous carbons (gCMK-3) were employed as support for Pt and Pt–Ru nanoparticles synthesized by different reduction methods. The catalysts displayed metal contents and Pt:Ru atomic ratios close to 20 wt % and 1:1, respectively. A comparison of the [...] Read more.
In this work, graphitized ordered mesoporous carbons (gCMK-3) were employed as support for Pt and Pt–Ru nanoparticles synthesized by different reduction methods. The catalysts displayed metal contents and Pt:Ru atomic ratios close to 20 wt % and 1:1, respectively. A comparison of the physical parameters of Pt and Pt–Ru catalysts demonstrated that Ru enters into the Pt crystal structure, with well-dispersed nanoparticles on the carbon support. The Pt catalysts exhibited similar surface oxide composition, whereas a variable content of surface Pt and Ru oxides was found for the Pt–Ru catalysts. As expected, the Pt–Ru catalysts showed low CO oxidation onset and peak potentials, which were attributed to the high relative abundances of both metallic Pt and Ru oxides. All the studied catalysts exhibited higher maximum current densities than those observed for the commercial Pt and Pt–Ru catalysts, although the current–time curves at 0.6 V vs. reversible hydrogen electrode (RHE) demonstrated a slightly higher stationary current density in the case of the Pt/C commercial catalyst compared with Pt nanoparticles supported on gCMK-3s. However, the stationary currents obtained from the Pt–Ru/gCMK-3 catalysts surpassed those of the commercial Pt–Ru material, suggesting the suitability of the prepared catalysts as anodes for these devices. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Ir-Ni Bimetallic OER Catalysts Prepared by Controlled Ni Electrodeposition on Irpoly and Ir(111)
Surfaces 2018, 1(1), 165-186; https://doi.org/10.3390/surfaces1010013
Received: 26 November 2018 / Revised: 12 December 2018 / Accepted: 13 December 2018 / Published: 14 December 2018
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Abstract
The alteration of electrocatalytic surfaces with adatoms lead to structural and electronic modifications promoting adsorption, desorption, and reactive processes. This study explores the potentiostatic electrodeposition process of Ni onto polycrystalline Ir (Irpoly) and assesses the electrocatalytic properties of the resulting bimetallic [...] Read more.
The alteration of electrocatalytic surfaces with adatoms lead to structural and electronic modifications promoting adsorption, desorption, and reactive processes. This study explores the potentiostatic electrodeposition process of Ni onto polycrystalline Ir (Irpoly) and assesses the electrocatalytic properties of the resulting bimetallic surfaces. The electrodeposition resulted in bimetallic Ni overlayer (OL) structures and in combination with controlled thermal post-deposition annealing in bimetallic near-surface alloys (NSA). The catalytic oxygen evolution reaction (OER) activity of these two different Ni-modified catalysts is assessed and compared to a pristine, unmodified Irpoly. An overlayer of Ni on Irpoly showed superior performance in both acidic and alkaline milieu. The reductive annealing of the OL produced a NSA of Ni, which demonstrated enhanced stability in an acidic environment. The remarkable activity and stability improvement of Ir by Ni modification makes both systems efficient electrocatalysts for water oxidation. The roughness factor of Irpoly is also reported. With the amount of deposited Ni determined by inductively coupled plasma mass spectrometry (ICP-MS) and a degree of coverage (monolayer) in the dependence of deposition potential is established. The density functional theory (DFT) assisted evaluation of H adsorption on Irpoly enables determination of the preferred Ni deposition sites on the three low-index surfaces (111), (110), and (100). Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Metallic Iridium Thin-Films as Model Catalysts for the Electrochemical Oxygen Evolution Reaction (OER)—Morphology and Activity
Surfaces 2018, 1(1), 151-164; https://doi.org/10.3390/surfaces1010012
Received: 3 November 2018 / Revised: 2 December 2018 / Accepted: 5 December 2018 / Published: 6 December 2018
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Abstract
Iridium (Ir) oxide is known to be one of the best electrocatalysts for the oxygen evolution reaction (OER) in acidic media. Ir oxide-based materials are thus of great scientific interest in current research on electrochemical energy conversion. In the present study, we applied [...] Read more.
Iridium (Ir) oxide is known to be one of the best electrocatalysts for the oxygen evolution reaction (OER) in acidic media. Ir oxide-based materials are thus of great scientific interest in current research on electrochemical energy conversion. In the present study, we applied Ir metal films as model systems for electrochemical water splitting, obtained by inductive heating in a custom-made setup using two different synthesis approaches. X-ray photoelectron spectroscopy (XPS) and selected area electron diffraction (SAED) confirmed that all films were consistently metallic. The effects of reductive heating time of calcined and uncalcined Ir acetate films on OER activity were investigated using a rotating disk electrode (RDE) setup. The morphology of all films was determined by scanning electron microscopy (SEM). The films directly reduced from the acetate precursor exhibited a strong variability of their morphology and electrochemical properties depending on heating time. The additional oxidation step prior to reductive heating accelerates the final structure formation. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Diazonium Salts: Versatile Molecular Glues for Sticking Conductive Polymers to Flexible Electrodes
Surfaces 2018, 1(1), 43-58; https://doi.org/10.3390/surfaces1010005
Received: 20 June 2018 / Revised: 20 July 2018 / Accepted: 22 July 2018 / Published: 8 August 2018
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Abstract
Adhesion of polymers to surfaces is of the upmost importance in timely applications such as protective coatings, biomaterials, sensors, new power sources and soft electronics. In this context, this work examines the role of molecular interactions in the adhesion of polypyrrole thin films [...] Read more.
Adhesion of polymers to surfaces is of the upmost importance in timely applications such as protective coatings, biomaterials, sensors, new power sources and soft electronics. In this context, this work examines the role of molecular interactions in the adhesion of polypyrrole thin films to flexible Indium Tin Oxide (ITO) electrodes grafted with aryl layers from various diazonium salts, namely 4-carboxybenzenediazonium (ITO-CO2H), 4-sulfonicbenzenediazonium (ITO-SO3H), 4-N,N-dimethylbenzenediazonium (ITO-N(CH3)2), 4-aminobenzenediazonium (ITO-NH2), 4-cyanobenzenediazonium (ITO-CN) and 4-N-phenylbenzenediazonium (ITO-NHPh). It was demonstrated that PPy thin layers were adherent to all aryl-modified surfaces, whereas adhesive failure was noted for bare ITO following simple solvent washing or sonication. Adhesion of polypyrrole was investigated in terms of hydrophilic/hydrophobic character of the underlying aryl layer as probed by contact angle measurements. It was found that sulfonic acid-doped polypyrrole (PPy-BSA) thin films were preferably deposited on the most hydrophobic surfaces. More importantly, the redox properties and electrochemical impedance of PPy were closely related to the hydrophobic character of the aryl layers. This work demonstrates that diazonium compounds are unique molecular glues for conductive polymers and permit to tune their interfacial properties. With robust, diazonium-based architectured interfaces, one can design high performance materials for e.g., sensors, printed soft electronics and flexible thermoelectrics. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
On the Contrasting Effect Exerted by a Thin Layer of CdS against the Passivation of Silver Electrodes Coated with Thiols
Surfaces 2018, 1(1), 29-42; https://doi.org/10.3390/surfaces1010004
Received: 14 June 2018 / Revised: 27 July 2018 / Accepted: 27 July 2018 / Published: 31 July 2018
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Abstract
The passivation of metal electrodes covered by self-assembled monolayers of long-chain thiols is well known. The disappearance of the voltammetric peak of redox species in solution is a classical test for the formation of full layers of thiols. Similar studies on semiconductors are [...] Read more.
The passivation of metal electrodes covered by self-assembled monolayers of long-chain thiols is well known. The disappearance of the voltammetric peak of redox species in solution is a classical test for the formation of full layers of thiols. Similar studies on semiconductors are still very limited. We used silver surfaces covered by an ultrathin layer of CdS as substrate for self-assembling of n-hexadecanethiol (C16SH), and we compared the experimental results with those obtained by using the bare silver surface as substrate. The strong insulating effect of C16SH deposited on Ag(III) is shown by the inhibition of the voltammetric peak of Ru(NH3)63+/2+. On the contrary, the voltammogram obtained on CdS-covered Ag(III) is very similar to that obtained on the bare Ag(III) electrode, thus suggesting that the presence of CdS exerts a contrasting effect on the passivation of the silver electrode. A crucial point of our work is to demonstrate the effective formation of C16SH monolayers on Ag(III) covered by CdS. The formation of full layers of C16SH was strongly suggested by the inhibition of the stripping peak of Cd from the CdS deposit covered by C16SH. The presence of C16SH was confirmed by electrochemical quartz crystal microbalance (EQCM) measurements as well as by Auger electron spectroscopy (AES) analysis. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Potential Driven Non-Reactive Phase Transitions of Ordered Porphyrin Molecules on Iodine-Modified Au(100): An Electrochemical Scanning Tunneling Microscopy (EC-STM) Study
Surfaces 2018, 1(1), 12-28; https://doi.org/10.3390/surfaces1010003
Received: 3 July 2018 / Revised: 22 July 2018 / Accepted: 24 July 2018 / Published: 25 July 2018
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Abstract
The modelling of long-range ordered nanostructures is still a major issue for the scientific community. In this work, the self-assembly of redox-active tetra(N-methyl-4-pyridyl)-porphyrin cations (H2TMPyP) on an iodine-modified Au(100) electrode surface has been studied by means of Cyclic Voltammetry [...] Read more.
The modelling of long-range ordered nanostructures is still a major issue for the scientific community. In this work, the self-assembly of redox-active tetra(N-methyl-4-pyridyl)-porphyrin cations (H2TMPyP) on an iodine-modified Au(100) electrode surface has been studied by means of Cyclic Voltammetry (CV) and in-situ Electrochemical Scanning Tunneling Microscopy (EC-STM) with submolecular resolution. While the CV measurements enable conclusions about the charge state of the organic species, in particular, the potentio-dynamic in situ STM results provide new insights into the self-assembly phenomena at the solid-liquid interface. In this work, we concentrate on the regime of positive electrode potentials in which the adsorbed molecules are not reduced yet. In this potential regime, the spontaneous adsorption of the H2TMPyP molecules on the anion precovered surface yields the formation of up to five different potential-dependent long-range ordered porphyrin phases. Potentio-dynamic STM measurements, as a function of the applied electrode potential, show that the existing ordered phases are the result of a combination of van der Waals and electrostatic interactions. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Open AccessArticle
Switchable Interfaces: Redox Monolayers on Si(100) by Electrochemical Trapping of Alcohol Nucleophiles
Surfaces 2018, 1(1), 3-11; https://doi.org/10.3390/surfaces1010002
Received: 29 June 2018 / Accepted: 17 July 2018 / Published: 20 July 2018
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Abstract
Organic electrosynthesis is going through its renaissance but its scope in surface science as a tool to introduce specific molecular signatures at an electrode/electrolyte interface is under explored. Here, we have investigated an electrochemical approach to generate in situ surface-tethered and highly-reactive carbocations. [...] Read more.
Organic electrosynthesis is going through its renaissance but its scope in surface science as a tool to introduce specific molecular signatures at an electrode/electrolyte interface is under explored. Here, we have investigated an electrochemical approach to generate in situ surface-tethered and highly-reactive carbocations. We have covalently attached an alkoxyamine derivative on an Si(100) electrode and used an anodic bias stimulus to trigger its fragmentation into a diffusive nitroxide (TEMPO) and a surface-confined carbocation. As a proof-of-principle we have used this reactive intermediate to trap a nucleophile dissolved in the electrolyte. The nucleophile was ferrocenemethanol and its presence and surface concentration after its reaction with the carbocation were assessed by cyclic voltammetry. The work expands the repertoire of available electrosynthetic methods and could in principle lay the foundation for a new form of electrochemical lithography. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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Review

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Open AccessReview
Time-Resolved X-ray Absorption Spectroscopy in (Photo)Electrochemistry
Surfaces 2018, 1(1), 138-150; https://doi.org/10.3390/surfaces1010011
Received: 7 November 2018 / Revised: 30 November 2018 / Accepted: 1 December 2018 / Published: 5 December 2018
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Abstract
This minireview aims at providing a complete survey concerning the use of X-ray absorption spectroscopy (XAS) for time-resolved studies of electrochemical and photoelectrochemical phenomena. We will see that time resolution can range from the femto-picosecond to the second (or more) scale and that [...] Read more.
This minireview aims at providing a complete survey concerning the use of X-ray absorption spectroscopy (XAS) for time-resolved studies of electrochemical and photoelectrochemical phenomena. We will see that time resolution can range from the femto-picosecond to the second (or more) scale and that this joins the valuable throughput typical of XAS, which allows for determining the oxidation state of the investigated element, together with its local structure. We will analyze four different techniques that use different approaches to exploit the in real time capabilities of XAS. These are quick-XAS, energy dispersive XAS, pump & probe XAS and fixed-energy X-ray absorption voltammetry. In the conclusions, we will analyze possible future perspectives for these techniques. Full article
(This article belongs to the Special Issue Electrochemical Surface Science: Basics and Applications)
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