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Juan M. Feliu - One of the best experts on this subject based on the ideXlab platform.
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effects of the Anion Adsorption and ph on the formic acid oxidation reaction on pt 111 electrodes
Electrochimica Acta, 2014Co-Authors: Juan V Peralesrondon, Enrique Herrero, Juan M. FeliuAbstract:Abstract The effects of solution pH and Anion Adsorption for the formic acid oxidation reaction on the Pt(111) electrode have been examined using electrochemical techniques. Regarding the pH effects, it has been found that oxidation currents for this reaction increase with pH, which indicates that solution formate is involved in the reaction mechanism. Unexpectedly, the Adsorption of sulfate on the Pt(111) electrode has a positive effect on the oxidation of formic acid, which also suggests that adsorbed Anions are also involved in the mechanism. The activation energy calculated from temperature dependent measurements diminishes with the solution pH and also in the presence of adsorbed sulfate. These measurements corroborate the involvement of solution formate and Anions in the oxidation mechanism. Using these results, a rate equation for the oxidation of formic acid is proposed. The current values calculated from this equation are in very good agreement with the experimental currents in perchloric acid solutions.
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Effects of the Anion Adsorption and pH on the formic acid oxidation reaction on Pt(111) electrodes
Electrochimica Acta, 2014Co-Authors: Juan V. Perales-rondon, Enrique Herrero, Juan M. FeliuAbstract:The effects of solution pH and Anion Adsorption for the formic acid oxidation reaction on the Pt(111) electrode have been examined using electrochemical techniques. Regarding the pH effects, it has been found that oxidation currents for this reaction increase with pH, which indicates that solution formate is involved in the reaction mechanism. Unexpectedly, the Adsorption of sulfate on the Pt(111) electrode has a positive effect on the oxidation of formic acid, which also suggests that adsorbed Anions are also involved in the mechanism. The activation energy calculated from temperature dependent measurements diminishes with the solution pH and also in the presence of adsorbed sulfate. These measurements corroborate the involvement of solution formate and Anions in the oxidation mechanism. Using these results, a rate equation for the oxidation of formic acid is proposed. The current values calculated from this equation are in very good agreement with the experimental currents in perchloric acid solutions.This work has been financially supported by the MICINN (Spain)(project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045, FEDER)
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Surface structure and Anion effects in the oxidation of ethanol on platinum nanoparticles
Journal of Materials Chemistry A, 2013Co-Authors: Carlos Busó-rogero, Enrique Herrero, Vitali Grozovski, Francisco J. Vidal-iglesias, José Solla-gullón, Juan M. FeliuAbstract:Ethanol oxidation on platinum nanoparticles with well-characterized surfaces is studied using cyclic voltammetry and FTIR techniques. Their behavior is compared with that obtained for platinum single crystal electrodes, in order to rationalize their performance and to understand the effects of the surface structure and Anion Adsorption on the reactivity. The results clearly demonstrate that there are strong effects of Anion Adsorption and surface structure on the measured current and oxidation mechanism. Thus, the main product of ethanol oxidation on (111) preferentially oriented Pt nanoparticles is acetic acid, and the amount of CO2 produced can be considered negligible. On the other hand, (100) preferentially oriented Pt nanoparticles are effective for the cleavage of the C–C bond yielding adsorbed CO, which eventually is oxidized to CO2. This nanoparticles electrode has the highest catalytic activity at high potentials, whereas (111) preferentially oriented Pt nanoparticles are more active at low potentials. In addition, no significant differences in the activity are reported by using different supporting electrolytes, which indicates that adsorbed acetate, which results from the Adsorption of acetic acid, hinders ethanol oxidation.This work has been financially supported by the MCINN-FEDER (Spain) (project CTQ 2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045)
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pt 1 1 1 surface disorder kinetics in perchloric acid solutions and the influence of specific Anion Adsorption
Electrochimica Acta, 2012Co-Authors: Ana M Gomezmarin, Juan M. FeliuAbstract:Abstract A significant number of electro-catalytic reactions take place in a potential region in which the surface of platinum is partly covered by oxygenated species. In this respect, the initial oxidation of Pt surfaces is an important process that could determine the reactivity of this catalyst. The understanding of electrochemical Pt oxidation has been hindered by a lack of surface structural definition. In this work, the electro-oxidation of Pt(1 1 1) electrode in the absence and presence of weak and moderately strong specific Anion Adsorption, and the subsequent surface modification induced by oxygen Adsorption are studied. Two different potential dependences are found for the surface reordering kinetics in perchloric acid solutions, at higher and lower potentials, whereas only one appears on sulphate containing solutions. Additionally, a dual role of sulphate Anion is observed: at high sulphate concentrations the protective character of the ordered sulphate adlayer delays surface disordering while small concentrations of sulphate Anions increase the rate of surface reordering. Water dissociation is at the origin of the double behaviour in HClO 4 and also explains the dual role of sulphate Anions. It is concluded that platinum oxidation is a complex process that involves several adsorbed species that appear at increasing potentials. All of these process are influenced by Anion Adsorption and coexist during the initial stages of Pt(1 1 1) oxidation.
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Electrochemical Oxidation of Pt(1 1 1) Vicinal Surfaces: Effects of Surface Structure and Specific Anion Adsorption
The Journal of Physical Chemistry C, 2011Co-Authors: Alexander Björling, Enrique Herrero, Juan M. FeliuAbstract:The initial oxidation of Pt surfaces is an important process that could determine the reactivity of catalysts in a wide range of reactions, from electrocatalytic oxidation of organics to oxygen reduction, but the understanding of electrochemical Pt oxidation has been hindered by a lack of surface-structural definition. We have investigated the process at surfaces vicinal to Pt(111) and show that these oxidize in successive stages depending on site geometry as well as the Adsorption behavior of the electrolyte Anion. Step sites of {100} orientation slowly oxidize at low potential (0.7 V vs RHE) in a region overlapping that of the “butterfly” peak seen at Pt(111) in the absence of specific electrolyte Anion Adsorption. Almost regardless of the latter, both {110} and {100} steps also oxidize between 0.9 and 1.2 V, causing voltammetric peaks with shapes that are characteristic of step orientation. The complex oxidation behavior of Pt(111) in perchloric acid, ranging from 0.6 V to the onset of O2 evolution at ...
Michael J Janik - One of the best experts on this subject based on the ideXlab platform.
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acetate and phosphate Anion Adsorption linear sweep voltammograms simulated using density functional theory
Electrochimica Acta, 2011Co-Authors: Iman Shahidi Pour Savizi, Michael J JanikAbstract:Abstract Specific Adsorption of Anions to electrode surfaces may alter the rates of electrocatalytic reactions. Density functional theory (DFT) methods are used to predict the Adsorption free energy of acetate and phosphate Anions as a function of Pt(1 1 1) electrode potential. Four models of the electrode potential are used including a simple vacuum slab model, an applied electric field model with and without the inclusion of a solvating water bi-layer, and the double reference model. The linear sweep voltammogram (LSV) due to Anion Adsorption is simulated using the DFT results. The inclusion of solvation at the electrochemical interface is necessary for accurately predicting the Adsorption peak position. The Langmuir model is sufficient for predicting the Adsorption peak shape, indicating coverage effects are minor in altering the LSV for acetate and phosphate Adsorption. Anion Adsorption peak positions are determined for solution phase Anion concentrations present in microbial fuel cells and microbial electrolysis cells and discussion is provided as to the impact of Anion Adsorption on oxygen reduction and hydrogen evolution reaction rates in these devices.
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Acetate and phosphate Anion Adsorption linear sweep voltammograms simulated using density functional theory
Electrochimica Acta, 2011Co-Authors: Iman Shahidi Pour Savizi, Michael J JanikAbstract:Specific Adsorption of Anions to electrode surfaces may alter the rates of electrocatalytic reactions. Density functional theory (DFT) methods are used to predict the Adsorption free energy of acetate and phosphate Anions as a function of Pt(1 1 1) electrode potential. Four models of the electrode potential are used including a simple vacuum slab model, an applied electric field model with and without the inclusion of a solvating water bi-layer, and the double reference model. The linear sweep voltammogram (LSV) due to Anion Adsorption is simulated using the DFT results. The inclusion of solvation at the electrochemical interface is necessary for accurately predicting the Adsorption peak position. The Langmuir model is sufficient for predicting the Adsorption peak shape, indicating coverage effects are minor in altering the LSV for acetate and phosphate Adsorption. Anion Adsorption peak positions are determined for solution phase Anion concentrations present in microbial fuel cells and microbial electrolysis cells and discussion is provided as to the impact of Anion Adsorption on oxygen reduction and hydrogen evolution reaction rates in these devices. © 2011 Elsevier Ltd. All rights reserved
Matthias Arenz - One of the best experts on this subject based on the ideXlab platform.
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Kinetics, Assembling, and Conformation Control of L-Cysteine Adsorption on Pt Investigated by in situ FTIR Spectroscopy and QCM-D.
Chemphyschem : a European journal of chemical physics and physical chemistry, 2018Co-Authors: André H. B. Dourado, Matthias Arenz, Rubens A. Silva, Roberto M. Torresi, Paulo T. A. Sumodjo, Susana I. Córdoba De TorresiAbstract:A quartz crystal microbalance method with dissipation (QCM-D) and attenuated total reflection Fourier-transform infrared (ATR-FTIRS) spectroscopy were used to study the Adsorption of L-cysteine (L-Cys) on Pt. Through QCM-D, it was possible to verify that the viscoelastic properties of the adsorbed species play an important role in the Adsorption, rendering Sauerbrey's equation inapplicable. The modelling of QCM-D data exposed two different processes for the Adsorption reaction. The first one had an activation time and is fast, whereas the second is slow. These processes were also resolved by ATR-FTIRS and identified to be water and Anion Adsorption preceded by L-Cys Adsorption. Both techniques reveal that the degree of surface coverage is pH dependent. Spectroscopic data indicate that the conformation of L-Cys(ads) changes with pH and that the structures do not fully agree with those proposed in literature for other metallic surfaces. The assembling of the adsorbed monolayer appeared to be very fast, and it was not possible to determine or quantify this kinetics. The conformation is also controlled by applied potential, and the Anion Adsorption and interfacial water depends on the conformation of the adsorbed molecules.
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In Situ FTIR Spectroscopy: Probing the Electrochemical Interface during the Oxygen Reduction Reaction on a Commercial Platinum High‐Surface‐Area Catalyst
ChemCatChem, 2016Co-Authors: Markus Nesselberger, Matthias ArenzAbstract:In situ observation of Anion Adsorption on industrial high-surface-area catalysts is used for the first time under oxygen reduction reaction (ORR) conditions with a defined mass transport. For this purpose, a specially fabricated electrode is used for which the catalyst layer is spray-coated on top of a structured Au contact layer and applied to our recently developed in situ attenuated total reflectance FTIR wall-jet electrode. The designed interface allows us to track Anion Adsorption and measure the reaction rate simultaneously under mass controlled conditions. The observed absorption bands are caused by Anion interaction with the active phase and also the carbon support. If we analyze the absorption band intensity of adsorbed Anions as a function of the oxygen reduction reaction rate, the band intensity decreases with the onset of the ORR. This shows that ORR inhibition is a complex interplay between site blocking caused by Anion Adsorption and oxide formation.
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The Oxygen Reduction Reaction on Thin Palladium Films Supported on a Pt(111) Electrode
The Journal of Physical Chemistry B, 2003Co-Authors: Matthias Arenz, Thomas J. Schmidt, Klaus Wandelt, Philip N. Ross, Nenad M. MarkovicAbstract:The oxygen reduction reaction (ORR) in acid and alkaline solutions is investigated on thin Pd films (0 < θPd < 1.5 ML) supported on a Pt(111) electrode. In 0.1 M KOH, the general form of the current vs ϑPd relationship for the ORR has a volcano shape, with the maximum catalytic activity exhibited by a surface modified with 1 ML of Pd. However, if the amount of Pd deposited exceeds 1 ML, the reaction is inhibited and 1.5 ML of Pd are less active than unmodified Pt(111). In 0.1 M HClO4, none of the Pd films are more active than Pt(111). In solution containing Cl- (ca. 106−10-5 M), the inhibition on the Pt(111)−Pd electrode is much more severe than on bare Pt(111) due to stronger Anion Adsorption on Pd. We present an interpretation of the kinetics of the ORR on Pt modified by thin Pd films in alkaline and acid solution based on the electronic properties of the Pd films and how the electronic properties effect specific Anion Adsorption, the formation of OHad and the Adsorption of the reaction intermediates.
Akiko Aramata - One of the best experts on this subject based on the ideXlab platform.
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Anomalous induced Anion Adsorption on zinc ion underpotential deposition at Au(111) in the presence of halide ions
Electrochemistry Communications, 1999Co-Authors: Shin Takahashi, Kiyoshi Hasebe, Akiko AramataAbstract:Abstract Underpotential deposition (UPD) of Zn 2+ at Au(111) in phosphate solution with Cl − , Br − , and I − was studied by cyclic voltammetry (CV), focusing on the effects of halide species on Zn UPD for the determination of the induced Anion Adsorption on the UPD. The order of the Adsorption strength of the induced Anion on Zn UPD was found to be different from that of the specific Adsorption of I − >Br − >Cl − > PO 3− 4 ≥ SO 2− 4 > ClO − 4 at a substrate Au electrode. The adsorbed Anions induced on Zn UPD are not suggested to be halide ions but phosphate ions. Such anomalous tendency of Anion behavior has been recently proved for induced sulfate and phosphate Adsorption behavior on Zn UPD at a Pt electrode in the presence of chloride by the radiotracer method. This paper shows that the anomalous induced phosphate Adsorption on Zn UPD also takes place at Au(111) not only in the presence of chloride or bromide, but also in the presence of iodide in a phosphate solution.
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Specific Anion Adsorption in the course of upd of Zn2+ ions on platinum
Journal of Electroanalytical Chemistry, 1997Co-Authors: G. Horányi, Akiko AramataAbstract:Abstract The specific Anion Adsorption accompanying the upd of Zn 2+ ions on platinum electrodes has been studied by the radiotracer technique using 15 S labelled sulphate species and 36 Cl labelled Cl − ions. It has been found that sulphate ions adsorb readily on the top of Zn adatoms while the Adsorption strength of Cl −1 ions on the Zn adlayer is significantly lower than that of HSO 4 −1 (SO 4 2− ) ions. Indirect radiotracer evidence obtained from competitive Adsorption studies is presented concerning the relatively high adsorbability of H 2 PO 4 ions. It follows from the experimental results obtained that the calculation of mass and charge balance (involving the determination of the so-called electrosorption valence) requires the knowledge of the extent of the Anion Adsorption on the adatom layer.
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The kinetic study of specific Adsorption of phosphate species on Pt(111) in acidic solutions
Journal of Electroanalytical Chemistry, 1997Co-Authors: Toshihiro Fukuda, Akiko AramataAbstract:Abstract The study of the Adsorption/desorption mechanism of phosphate Anions at Pt(111) in acidic solution of pH 4.3 and 0.8 was performed by the potential step method in order to reveal the kinetics of Anion Adsorption. The current-time curve due to phosphate Adsorption/desorption showed various decay features, being dependent on the potential region. The rate of current decay depended on pH, being faster in a lower pH solution. Specific Adsorption processes were analyzed by the Langmuir and Elovich Adsorption equations and also in terms of a two-dimensional nucleation-growth mechanism in different Adsorption/desorption regions. In the case of Adsorption in 0.3M phosphate buffer solution of pH 4.3, random Adsorption without interaction following the Langmuir Adsorption, takes place at low coverage, while random Adsorption with repulsive force was observed at high coverage. In the desorption process, random desorption with repulsive force takes place at high coverage, and the repulsive force disappears where random Adsorption without interaction takes place at medium coverage. When the surface coverage becomes further lower, the desorption mechanism changes dramatically into a two-dimensional nucleation-growth type, suggesting that an ordered adsorbate structure is formed after a rapid discharge process of Anion Adsorption.
Sabine Goldberg - One of the best experts on this subject based on the ideXlab platform.
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application of surface complexation models to Anion Adsorption by natural materials
Environmental Toxicology and Chemistry, 2014Co-Authors: Sabine GoldbergAbstract:Various chemical models of ion Adsorption are presented and discussed. Chemical models, such as surface complexation models, provide a molecular description of Anion Adsorption reactions using an equilibrium approach. Two such models, the constant capacitance model and the triple layer model, are described in the present study. Characteristics common to all the surface complexation models are equilibrium constant expressions, mass and charge balances, and surface activity coefficient electrostatic potential terms. Methods for determining parameter values for surface site density, capacitances, and surface complexation constants also are discussed. Spectroscopic experimental methods of establishing ion Adsorption mechanisms include vibrational spectroscopy, nuclear magnetic resonance spectroscopy, electron spin resonance spectroscopy, X-ray absorption spectroscopy, and X-ray reflectivity. Experimental determinations of point of zero charge shifts and ionic strength dependence of Adsorption results and molecular modeling calculations also can be used to deduce Adsorption mechanisms. Applications of the surface complexation models to heterogeneous natural materials, such as soils, using the component additivity and the generalized composite approaches are described. Emphasis is on the generalized composite approach for predicting Anion Adsorption by soils. Continuing research is needed to develop consistent and realistic protocols for describing ion Adsorption reactions on soil minerals and soils. The availability of standardized model parameter databases for use in chemical speciation–transport models is critical. Environ Toxicol Chem 2014;33:2172–2180. Published 2014 Wiley Periodicals Inc. on behalf of SETAC. This article is a US Government work and as such, is in the public domain in the United States.
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Application of surface complexation models to Anion Adsorption by natural materials.
Environmental toxicology and chemistry, 2014Co-Authors: Sabine GoldbergAbstract:Various chemical models of ion Adsorption are presented and discussed. Chemical models, such as surface complexation models, provide a molecular description of Anion Adsorption reactions using an equilibrium approach. Two such models, the constant capacitance model and the triple layer model, are described in the present study. Characteristics common to all the surface complexation models are equilibrium constant expressions, mass and charge balances, and surface activity coefficient electrostatic potential terms. Methods for determining parameter values for surface site density, capacitances, and surface complexation constants also are discussed. Spectroscopic experimental methods of establishing ion Adsorption mechanisms include vibrational spectroscopy, nuclear magnetic resonance spectroscopy, electron spin resonance spectroscopy, X-ray absorption spectroscopy, and X-ray reflectivity. Experimental determinations of point of zero charge shifts and ionic strength dependence of Adsorption results and molecular modeling calculations also can be used to deduce Adsorption mechanisms. Applications of the surface complexation models to heterogeneous natural materials, such as soils, using the component additivity and the generalized composite approaches are described. Emphasis is on the generalized composite approach for predicting Anion Adsorption by soils. Continuing research is needed to develop consistent and realistic protocols for describing ion Adsorption reactions on soil minerals and soils. The availability of standardized model parameter databases for use in chemical speciation-transport models is critical.
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Surface Complexation Modeling APPLICATION OF SURFACE COMPLEXATION MODELS TO Anion Adsorption BY NATURAL MATERIALS
2014Co-Authors: Sabine GoldbergAbstract:Various chemical models of ion Adsorption are presented and discussed. Chemical models, such as surface complexation models, provide a molecular description of Anion Adsorption reactions using an equilibrium approach. Two such models, the constant capacitance model and the triple layer model, are described in the present study. Characteristics common to all the surface complexation models are equilibrium constant expressions, mass and charge balances, and surface activity coefficient electrostatic potential terms. Methods for determining parameter values for surface site density, capacitances, and surface complexation constants also are discussed. Spectroscopic experimental methods of establishing ion Adsorption mechanisms include vibrational spectroscopy, nuclear magnetic resonance spectroscopy, electron spin resonance spectroscopy, X-ray absorption spectroscopy, and X-ray reflectivity. Experimental determinations of pointof zero charge shiftsand ionic strength dependence ofAdsorption results and molecular modelingcalculations also can be used to deduce Adsorption mechanisms. Applications of the surface complexation models to heterogeneous natural materials, such as soils, using the component additivity and the generalized composite approaches are described. Emphasis is on the generalized composite approach for predicting Anion Adsorption by soils. Continuing research is needed to develop consistent and realistic protocols for describing ion Adsorption reactions on soil minerals and soils. The availability of standardized model parameter databases for use in chemical speciation-transport models is critical. Environ Toxicol Chem 2014;33:2172-2180. Published 2014 Wiley Periodicals Inc. on behalf of SETAC. This article is a US Government work and as such, is in the public domain in the United States.