Probing Electrochemical Adsorbate Structure and Reactions with In-Situ Atomic-Resolution Scanning Microscopy: Some Progress and Prospects PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages : 38
Book Description
Some prospects for applying scanning tunneling microscopy (STM) as an in-situ atomic-resolution probe of adlayer structure at ordered metal-solution interfaces are considered with respect to both equilibrium and reactive adsorbate systems. Illustrative results of the former type are presented for the potential-dependent adsorption of iodide at low-index gold electrodes. The virtues of acquiring composite-domain STM Images, where the electrode potential is altered during data acquisition so to form or remove the adsorbed adlayer, are noted. By generating temporally and spatially adjacent domains featuring substrate and adlayer images in this fashion, the registry between the former and latter atomic arrangements can be deduced with high precision. The suitability of in-situ STM for examining real-space dynamics of surface physical and chemical processes is illustrated for potential-induced reconstruction of Au(100) and for the electrooxidative polymerization of iodide and sulfide. Some limitations as well as strengths of in-situ STM for these purposes are briefly outlined with regard to its anticipated role in the development of in-situ electrochemical surface science. STM, COMPOSITE-DOMAIN IMAGES, ELECTROOXIDATIVE POLYMERIZATION.
Author: Publisher: ISBN: Category : Languages : en Pages : 38
Book Description
Some prospects for applying scanning tunneling microscopy (STM) as an in-situ atomic-resolution probe of adlayer structure at ordered metal-solution interfaces are considered with respect to both equilibrium and reactive adsorbate systems. Illustrative results of the former type are presented for the potential-dependent adsorption of iodide at low-index gold electrodes. The virtues of acquiring composite-domain STM Images, where the electrode potential is altered during data acquisition so to form or remove the adsorbed adlayer, are noted. By generating temporally and spatially adjacent domains featuring substrate and adlayer images in this fashion, the registry between the former and latter atomic arrangements can be deduced with high precision. The suitability of in-situ STM for examining real-space dynamics of surface physical and chemical processes is illustrated for potential-induced reconstruction of Au(100) and for the electrooxidative polymerization of iodide and sulfide. Some limitations as well as strengths of in-situ STM for these purposes are briefly outlined with regard to its anticipated role in the development of in-situ electrochemical surface science. STM, COMPOSITE-DOMAIN IMAGES, ELECTROOXIDATIVE POLYMERIZATION.
Author: Arthur T. Hubbard Publisher: CRC Press ISBN: 9780824707576 Category : Science Languages : en Pages : 1580
Book Description
This comprehensive reference collects fundamental theories and recent research from a wide range of fields including biology, biochemistry, physics, applied mathematics, and computer, materials, surface, and colloid science-providing key references, tools, and analytical techniques for practical applications in industrial, agricultural, and forensic processes, as well as in the production of natural and synthetic compounds such as foods, minerals, paints, proteins, pharmaceuticals, polymers, and soaps.
Author: Publisher: ISBN: Category : Languages : en Pages : 35
Book Description
In-situ atomic-resolution scanning tunneling microscopy (STM) has been utilized on ordered Au(lll) under electrode potential control in acidic aqueous solution to examine iodine adlayer structures formed by iodide electrooxidation as well as electrosorption. In the potential region, -0. 3 to 0. 4 V vs SCE, below where electrooxidation of solution iodide occurs, several distinct iodine adlayer structures were observed. At the most negative potentials, structures close to the hexagonal ((check)3 x (check)3) R30 deg (Theta = 0.33) pattern are evident. The registry between the adlayer and the substrate lattice was deduced in part from composite domain images created by stepping the electrode potential so to alter markedly the adsorbate coverage during acquisition of a given STM image. At potentials between -0.2 and 0.2 V, adlayer patterns closer to the (5 x (check)3) (Theta = 0.4) structure became increasingly prevalent. This features a diminution in the iodine spacing along two of the three iodine rows, with a corresponding ca 5 deg shift from the R30 deg direction. Above 0.2 V, the STM images indicated the predominant presence of a more complex higher-coverage adlayer (Theta = 0.44) featuring long-range (19+/-lA) Z corrugations rotated by 8-10 deg from the hexagonal iodine adlattice. These corrugations arise from periodic alterations in the iodine binding site, necessitated by I-I distances that approach the van der Waals diameter. Above 0. 3 V, however, poly-iodide chains were also observed, featuring shorter (2.8 - 3. 2 A) I-I distances compatible with adsorbate-adsorbate chemical bonding; these increasingly distort the monomeric iodine superlattice structure.
Author: Johannes G. Vos Publisher: John Wiley & Sons ISBN: 0470861509 Category : Science Languages : en Pages : 332
Book Description
Describes the supramolecular properties of molecular assemblies that contain a solid phase, offering an integrated approach to measurement and addressibility. * Offers an integrated approach to measurement and addressibility. * Features case studies describing the major devices developed using this technology. * The prospects for the future of interfacial supramolecular assemblies are considered.
Author: S. Ray Taylor Publisher: ISBN: Category : Science Languages : en Pages : 418
Book Description
The 31 papers discuss various methods for analyzing electrochemical interfaces to find and identify local phenomena such as corrosion, electrocrystallization, electrocatalysis, and membrane-based separations that might affect the electrochemical process. The methods include atomic force and scanning tunneling microscopy, optical methods, scanning electrochemical microscopy, local impedance and current, and scanning Kelvin probe. c. Book News Inc.
Author: Alex Mirabal Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 164
Book Description
Efficient, sustainable chemical reactions will play a large role in addressing many growing issues, including alternative energy production, greenhouse gas conversion, and pharmaceuticals. Electrochemical reactions are attractive due to their relatively mild reaction conditions and direct use of electricity. The understanding and design of the local liquid-solid interface will guide future progress in electrocatalytic reactions.Over time, nature has evolved many highly efficient reactions through enzymatic reactions. These long-studied catalysts provide complex reaction environments that: 1) enhance interaction with reactants, 2) protect intermediates from side reactions, 3) increase the rates of reactions, and 4) selectively react to a specific product. The overarching lesson to be learned is that the local reaction environment plays a large role in the catalyst's reactivity, selectivity, and efficiency. One way to characterize the local environment is through scanning electrochemical microscopy (SECM), in which a small electrochemical probe is rastered over an interface. A quantitative correlation of the probe response to concentration provides a direct measurement of the local environment.The presence of the SECM probe itself can induce changes in the local environment. Comparing the changed local environment (in situ) to what it would be without the probe present (operando), shows large differences of up to 120% under specific operating conditions. A few physical parameters such as the surface site geometry are shown to have an impact on how significant the probe effects are. Additional parameters such as the tip geometry and tip-surface separation are also to have an impact.A finite element method (FEM) simulation informed by experiments is used to examine the above-mentioned tip effects. It is found that fitting responses to other frequently used electrochemical measurements, such as approach curves and CVs, to parameterize the model appropriately describes experimental SECM results. We first apply this method to study platinum nanoparticles, where a ~50 nm resolution is the highest resolution to our knowledge for AFM-SECM. Through statistical analysis of the surface, an isolated nanoparticle SECM response is correlated with a concentration profile. It is found that the concentration profile has minimal probe effects due to the use of a conical electrode.Applying a similar approach, we also study the probe effects in pH detection during hydrogen evolution and CO2 reduction. Where we match experimental results to parameterize the system. It shown that there is a pH difference of up to ~7 pH units underneath the probe due to hindered diffusion. However, even with these large differences, the probes are still able to reflect the trends seen without the probe present. Moreover, it is shown that the physical parameters have correlated responses, indicating that hindered diffusion is controlled by the insulation radius and tip-surface separation.Finally, the importance of the analyte is discussed with regard to its interaction with the tip. In addition to the concentration impact on the response signal, the compatibility with the tip need be considered. Degradation of the tip and/or the redox couple of choice will detrimentally affect the ability to examine the local interface. We show that, of the redox couples examined, ferrocene-based compounds appear to best satisfy the most crucial factors of stability and mild redox potentials.Overall, this work studies and removes the impact of the probe for local concentration detection using SECM. This work acts as a guide to quantitatively study the local environment of electrocatalyzed reactions. This is realized through a combined experimental-FEM approach in which the simulation is informed by experiments such that it's representative of the experimental environment.
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Author: Arthur T. Hubbard
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Author: Johannes G. Vos
Author: S. Ray Taylor
Author: Alex Mirabal
Author: Xudong Jiang