Investigation of the Structure-activity Relationship of Pseudo-single-crystal Platinum Electrodes by Scanning Electrochemical Microscopy PDF Download
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Author: Yulin Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 157
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The study of the structure-activity relationship of electrode surfaces is fundamentally important in electrocatalysis research. Yet, the methods and techniques used for the examination of structure-activity relationship so far are limited by their capabilities, and the exploration of electrochemistry at complex surfaces is very challenging. In this study, the correlation between the electrode surface structure and its corresponding activity in two electrochemical reactions were investigated: an electrochemical etching reaction and an electrocatalysis reaction. A polycrystalline Pt electrode was galvanically etched to expose the underlying well-defined crystallites serving as pseudo-single-crystal electrodes. Atomic force microscopy (AFM) complemented with electron backscatter diffraction (EBSD) was employed for the elucidation of the effects of electrode surface structure on its etching rate. Electrochemical measurements of the electrocatalytic activity of the hydrogen oxidation reaction on individual grain surfaces were performed with high spatial resolution scanning electrochemical microscopy (SECM) coupled with electron backscatter diffraction (EBSD). The etching experiment and surface characterization results show the more deeply etched regions on polycrystalline Pt surface correspond to Pt(100). The etching rate of the Pt catalyst is Pt(111), Pt(100), and Pt(110) in increasing order. The structure-reactivity relationship showed that the catalytic activity for hydrogen oxidation reaction (HOR) increases in the order Pt(100)
Author: Yulin Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 157
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Book Description
The study of the structure-activity relationship of electrode surfaces is fundamentally important in electrocatalysis research. Yet, the methods and techniques used for the examination of structure-activity relationship so far are limited by their capabilities, and the exploration of electrochemistry at complex surfaces is very challenging. In this study, the correlation between the electrode surface structure and its corresponding activity in two electrochemical reactions were investigated: an electrochemical etching reaction and an electrocatalysis reaction. A polycrystalline Pt electrode was galvanically etched to expose the underlying well-defined crystallites serving as pseudo-single-crystal electrodes. Atomic force microscopy (AFM) complemented with electron backscatter diffraction (EBSD) was employed for the elucidation of the effects of electrode surface structure on its etching rate. Electrochemical measurements of the electrocatalytic activity of the hydrogen oxidation reaction on individual grain surfaces were performed with high spatial resolution scanning electrochemical microscopy (SECM) coupled with electron backscatter diffraction (EBSD). The etching experiment and surface characterization results show the more deeply etched regions on polycrystalline Pt surface correspond to Pt(100). The etching rate of the Pt catalyst is Pt(111), Pt(100), and Pt(110) in increasing order. The structure-reactivity relationship showed that the catalytic activity for hydrogen oxidation reaction (HOR) increases in the order Pt(100)
Author: Ugne Mitrikeviciute
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Christina M. Johnston
Publisher:
ISBN:
Category :
Languages : en
Pages : 508
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Author: Rachel L. Behrens
Publisher:
ISBN:
Category :
Languages : en
Pages :
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In support of the recent interest in fuels from renewable resources for fuel cells, the intermediates of the oxidation of formic acid and ethanol to CO2 on platinum electrodes have been examined. The adsorbed carbon monoxide intermediate continues to be the cause for a decrease in efficiency and activity for platinum electrodes and is the leading surface poison (intermediate) in the most common oxidation reactions. We have studied the CO species generated from both fuel and CO-saturated media to observe site conversion of the CO species on polycrystalline platinum and platinum single crystal surfaces with respect to concentration, composition of electrolyte, and potential with electrochemical techniques and broad-band sum frequency generation spectroscopy (BB-SFG). In situ BB-SFG allows for the chemical analysis of electrode surfaces to examine details of surface electrochemical reactions. SFG is based on a second order nonlinear optical process that is forbidden in centrosymmetric media. Therefore, SFG is intrinsically interface-sensitive and enables surface chemical measurements without contribution from the bulk. With the aid of a femtosecond IR laser, we probe vibrational transitions of adsorbates in real time on the electrode surface as the potential at the surface is scanned at rates up to 5 mV/s. Studies of CO species, other reaction intermediates, and adsorbates will be discussed in relation to their poisoning of catalysis by single crystal Pt electrodes. These experiments demonstrate the sensitivity of the BB-SFG technique to the adsorbed species, and its capability to examine adsorption site conversions of the species on the electrode surface. In formic acid fuel solution, in situ BB-SFG was used to obtain vibrational spectra of CO adsorbates produced from formic acid oxidation on a Pt(100) electrode in sulfuric acid and perchloric acid media. The BB-SFG simultaneously monitored all forms of the CO intermediates, including steady-state, as the potential was scanned at 5 mV/s. Spectra were compared to those obtained from CO adsorbed from a CO-saturated electrolyte. While adsorbed from HCOOH, CO had a sharp atop transition near 2050 cm-1 and a broader multiply-bonded transitions in the 1700-1900 cm-1 range, which appear to result from bridge-like and higher-coordinated (possibly fourfold) CO. As the potential was scanned from -0.2 to 0.3 V (vs. Ag/AgCl), the bridge-like CO disappeared and the amount of atop CO increased. At potentials above 0.5 V, CO was in steady-state, being oxidized on the surface to CO2 and replenished by CO from HCOOH. These measurements show that BB-SFG can observe potential-dependent interconversion of different CO forms on the electrode surface and can measure steady-state reaction intermediates on a surface in real time. In situ BB-SFG was also employed to study ethanol on platinum electrodes as a means to elucidate the mechanism of this reaction on catalyst surfaces for fuel cell applications. Recently, the interest in ethanol has increased, not only as a renewable resource, but especially as a fuel source due to its high theoretical yield of 12 electrons released upon complete oxidation. Incomplete oxidation, a major setback with ethanol oxidation, forms byproducts and intermediates slowing the oxidation reaction or prohibiting it from occurring further. Among the byproducts are acetic acid and acetaldehyde, where the C-C bond is not yet broken, or the intermediate CO, where the C-C bond has been broken and is further oxidized to CO2. Using simultaneous electrochemical techniques and broad-band sum frequency generation, these byproducts and intermediates formed on platinum electrodes will be discussed in both acidic and basic media, as a function of electrolyte composition and ethanol concentration.
Author: Xiaojing Sun
Publisher:
ISBN:
Category : Electrodes
Languages : en
Pages :
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The tip generation/substrate collection mode (TG/SC) of scanning electrochemical microscopy (SECM) was used to study the ORR reactivity on Pt catalysts in sulfuric acid solution. The SECM reactivity image and the photographic image of different single crystalline regions of the etched Pt electrode correlated well. The electron backscatter diffraction (EBSD) image of Pt confirmed the surface single crystalline orientation. The image resolution is improved by employing smaller tipsubstrate distance. The kinetics of the ORR on Pt surface was also studied at -15 - 30 °C by means of the rotating disk voltammetry techniques. The calculated Tafel slopes for 0.1 m and 0.9 m HClO4 changed with decreasing temperature, indicating lower kinetics at low temperature. Peroxide is produced at potentials below 0 V vs SCE.
Author: Toshiaki Ohtsuka
Publisher: Springer
ISBN: 9811068208
Category : Science
Languages : en
Pages : 123
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Book Description
This brief is concerned with the fundamentals of corrosion of metallic materials and electrochemistry for better understanding of corrosion phenomena. Corrosion is related to both the environment and material properties, induced by electrochemical reactions at the interface between metallic materials and the environment as in aqueous and gaseous phases. In order to understand corrosion phenomena, knowledge of electrochemistry is thus required, and to investigate the cause of corrosion damage, appropriate electrochemical experiments must be performed. Corrosion scientists should therefore possess knowledge of both electrochemistry and its related experimental techniques. In this book, corrosion phenomena are introduced from the electrochemical aspect. Electrochemical techniques for the study of corrosion are then described with other techniques that can be combined with electrochemistry. Because this brief is characterized as starting with the fundamentals of corrosion and electrochemistry, it is accessible to undergraduate students as well as to graduate students who are beginning corrosion research.
Author: Katherine Hunter
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Marcel Pourbaix
Publisher: Springer Science & Business Media
ISBN: 1468418068
Category : Science
Languages : en
Pages : 352
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Book Description
Workers in the field of corrosion and their students are most fortunate that a happy set of circumstances brought Dr. Marcel Pourbaix into their field in 1949. First, he was invited, while in the USA, to demonstrate at a two week visit to the National Bureau of Standards the usefulness of his electro chemical concepts to the study of corrosion. Secondly, also around the same time, Prof. H. H. Uhlig made a speech before the United Nations which pointed out the tremendous economic consequences of corrosion. Because of these circumstances, Dr. Pourbaix has reminisced, he chose to devote most of his efforts to corrosion rather than to electrolysis, batteries, geology, or any of the other fields where, one might add, they were equally valuable. This decision resulted in his establishing CEBELCOR (Centre BeIge d'Etude de la Corrosion) and in his development of a course at the Free University of Brussels entitled "Lectures on Electrochemical Corrosion." This book is the collection of these lectures translated into English.
Author: Allen J. Bard
Publisher: Wiley Global Education
ISBN: 1118312805
Category : Science
Languages : en
Pages : 862
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Book Description
Das führende Werk auf seinem Gebiet - jetzt durchgängig auf den neuesten Stand gebracht! Die theoretischen Grundlagen der Elektrochemie, erweitert um die aktuellsten Erkenntnisse in der Theorie des Elektronentransfers, werden hier ebenso besprochen wie alle wichtigen Anwendungen, darunter modernste Verfahren (Ultramikroelektroden, modifizierte Elektroden, LCEC, Impedanzspektrometrie, neue Varianten der Pulsvoltammetrie und andere). In erster Linie als Lehrbuch gedacht, läßt sich das Werk aber auch hervorragend zum Selbststudium und zur Auffrischung des Wissensstandes verwenden. Lediglich elementare Grundkenntnisse der physikalischen Chemie werden vorausgesetzt.
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Category :
Languages : en
Pages :
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