Quantitative Correlations between the Normal Incidence Differential Reflectance and the Coverage of Adsorbed Bromide on a Polycrystalline Platinum Rotating Disk Electrode

Xu, Jing; Scherson, Daniel Alberto

doi:10.1021/ac303322c

Cited by 9 publications

(12 citation statements)

References 24 publications

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“…This is illustrated in Fig. 12 which compares dynamic polarization curves recorded in this case using instrumentation specified in an earlier communication, 10 …”

mentioning

confidence: 96%

“…As is well known, 9 from 0.1 to 10 mM. The same all-Teflon cylindrical cell described in a previous communication 10 was employed for these studies. A Pt wire in the form of a coil inserted in a glass tube with a glass frit at its end, and a homemade reversible hydrogen in 0.1 M HClO 4 (RHE) were used as counter and reference electrodes respectively, and inserted into individual vertical holes drilled through the cap of the cell to connect to its main body.…”

mentioning

confidence: 99%

“…Experiments aimed at correlating bromide oxidation with Pt surface oxidation were performed under normal incidence using a laser employing an optical system and data acquisition strategies described in detail elsewhere. 10 Data are displayed in the form A(E) -A(E ref )…”

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confidence: 99%

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The Oxidation of Bromide on Platinum Electrodes in Aqueous Acidic Solutions: Electrochemical and In Situ Spectroscopic Studies

Georgescu

Scherson

2014

J. Electrochem. Soc.

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Certain aspects of the oxidation of bromide in acidic aqueous electrolytes have been investigated via a combination of rotating disk electrode (RDE) and in situ reflection absorption UV-visible spectroscopic techniques. Koutecky-Levich plots of polarization curves recorded with a Pt RDE in 5 mM KBr in 0.1M HClO 4 at rotation rates in the range 400 to 2000 rpm yielded for low overpotentials rates independent of the applied potential. This conclusion supports the reports of Conway et al. (J. Chem. Soc., Faraday Trans., 1995, 91, 283) which relied on the analysis of the results different type of experiments performed in more concentrated bromide solutions. Advantage was taken of the very high molar absorptivity of tribromide, i.e. ε(λ = 266 nm) = 4.09 × 10 7 cm 2 mol −1 , a solution phase species generated via the reaction of bromine and bromide, to monitor quantitatively its presence within the diffusion boundary layer and thus gain insights into the reaction mechanism. Numerical simulations of the electrochemical-chemical (EC) mechanism that take into account the dynamics of formation and dissociation of tribromide, yielded good agreement with both the optical and electrochemical data collected in this work under strict diffusion control. The development and optimization of efficient and economical means of storing energy from renewable and intermittent sources, including wind and solar, will have a pronounced impact toward mitigating problems derived from the depletion of oil reserves, as well as improve the way in which the electrical grid is currently managed. Although their capital costs per cycle are higher than those associated with pumped-storage hydroelectricity, the versatility of electrochemical energy storage devices, such as batteries, fuel cells and double layer capacitors may indeed hold the key to accomplishing these goals. Capacitors display very high power densities and sub-second response times and, as such, are suitable for power quality management. Batteries, on the other hand, including those of the flow redox type, and fuel cells, exhibit much higher specific energy densities than capacitors and therefore can meet the requirements of large-scale electrical energy storage.Whereas batteries store energy within, and, therefore, their energy and power densities are determined by the characteristics and size of its constituent electrodes, the redox active materials in a fuel cell (or redox flow battery) are stored externally; hence, their energy capacity is dictated by the size of the containers. The latter constitutes a great advantage, as in analogy to an internal combustion engine, the power and energy densities are governed, respectively, by the size of the engine and that of the fuel tank. In stark contrast, the energy of a battery of a specific chemistry can only be augmented by increasing the number of modules and thus of all its integral components, including among others, separators and current collectors. Yet another complicating factor relates to changes in the intrinsic structure, i...

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“…This is illustrated in Fig. 12 which compares dynamic polarization curves recorded in this case using instrumentation specified in an earlier communication, 10 …”

mentioning

confidence: 96%

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confidence: 99%

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The Oxidation of Bromide on Platinum Electrodes in Aqueous Acidic Solutions: Electrochemical and In Situ Spectroscopic Studies

Georgescu

Scherson

2014

J. Electrochem. Soc.

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“…290 K) in Ar (PP300, 99.998%, Airgas)-purged aqueous 0.1 M HClO 4 (70%, Ultrapure, EMD) solutions in ultrapure water (18.3 M cm, EASYpure UV system, Barnstead). The instrumentation and techniques employed were the same as those specified in detail elsewhere, 4,5 including a low-power red laser (Coherent Inc. Red Eagle 635-10, λ = 635 nm, 10 mW) aimed at normal incidence toward the center of the disk of a rotating ring disk electrode, RRDE, assembly, (Area = 0.164 cm 2 , Pine Instruments, Model AFE7R8PTPT). Potential control of the RRDE was achieved with a bipotentiostat (AFRDE5, Pine Instruments) and data were collected with an acquisition card (NI, USB-6009) connected to a personal computer.…”

Section: Methodsmentioning

confidence: 99%

Quantitative In Situ Differential Reflectance Spectroscopy Analysis of Polycrystalline Platinum Oxidation in an Aqueous Acidic Electrolyte

Scherson

2015

ECS Electrochemistry Letters

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A method is herein described that allows the coverage of the two forms of oxide believed to form on polycrystalline Pt, Pt(poly), surfaces in aqueous solutions to be determined based on the analysis of in situ differential reflectance spectroscopy, R/R, and voltammetric data recorded simultaneously. The model employed assumes R/R can be expressed as the sum of contributions due to each type of surface site, i, represented by the product of their potential dependent coverage, θ i (E), and a linear function of E obtained empirically. Values of θ i (E) for the unoxidized and oxidized sites are calculated by solving a system of three non-linear equations that relate θ i (E) to the charge associated with the formation of the oxide layer based on coulometric analyses and accepted values for the number of electrons transferred for each of the oxides. Data collected for Pt(poly) electrodes in aqueous 0.1 M HClO 4 was found to be consistent with the coexistence of the two forms of Pt oxide and unoxidized sites on the surface over a potential range extending from ca. Evidence has been obtained in our laboratories 1 that the differential reflectance of polycrystalline Pt, Pt(poly), electrodes in aqueous perchloric acid solutions up to potentials where only a single form of oxide is believed to form can be represented in terms of additive contributions due to the unoxidized or bare, and oxidized sites, expressed for each case in terms of the product of their corresponding potential dependent coverage, θ i (E), i = bare or oxidized, and a linear function of the applied potential, E. More recently, 2 this model was applied to the analysis of data collected on quasi perfect Pt(111) microfacets formed by melting and cooling the tip of Pt microwires, and found to account quantitatively for the optical response associated with the adsorption of hydrogen, hydroxyl, and bisulfate in acidic electrolytes.This brief communication seeks to extend this strategy to the oxidation of Pt(poly) surfaces in 0.1 M HClO 4 over a potential range wide enough to include the higher oxidation state Pt oxide.3 As will be shown, analyses of the data acquired made it possible to construct plots of the coverage of the unoxidized and the two forms of Pt oxide as a function of E. ExperimentalAll experiments were performed at room temperature (ca. 290 K) in Ar (PP300, 99.998%, Airgas)-purged aqueous 0.1 M HClO 4 (70%, Ultrapure, EMD) solutions in ultrapure water (18.3 M cm, EASYpure UV system, Barnstead). The instrumentation and techniques employed were the same as those specified in detail elsewhere, 4,5 including a low-power red laser (Coherent Inc. Red Eagle 635-10, λ = 635 nm, 10 mW) aimed at normal incidence toward the center of the disk of a rotating ring disk electrode, RRDE, assembly, (Area = 0.164 cm 2 , Pine Instruments, Model AFE7R8PTPT). Potential control of the RRDE was achieved with a bipotentiostat (AFRDE5, Pine Instruments) and data were collected with an acquisition card (NI, USB-6009) connected to a personal computer. After the electrode ...

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“…The poisoning occurs due to the adsorption of Br − species onto the active Pt catalyst sites. 21,39 As a result, the hydrogen atoms were deprived of active catalyst sites for reaction. Also, the Pt catalyst was corroded in the presence of Br 2 and Br 3 − species leading to the loss of active sites for the electrochemical reactions to occur.…”

Section: 35mentioning

confidence: 99%

A Comprehensive Study of an Acid-Based Reversible H₂-Br₂Fuel Cell System

Yarlagadda

Dowd

Park

et al. 2015

J. Electrochem. Soc.

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The regenerative H 2 -Br 2 fuel cell has been a subject of notable interest and is considered as one of the suitable candidates for large scale electrical energy storage. In this study, the preliminary performance of a H 2 -Br 2 fuel cell using both conventional as well as novel materials (Nafion and electrospun composite membranes along with Pt and Rh x S y electrocatalysts) is discussed. The performance of the H 2 -Br 2 fuel cell obtained with a conventional Nafion membrane and Pt electrocatalyst was enhanced upon employing a double-layer Br 2 electrode while raising the cell temperature to 45 • C. The active area and wetting characteristics of Br 2 electrodes were improved upon by either pre-treating with HBr or boiling them in de-ionized water. On the other hand, similar or better performances were obtained using dual fiber electrospun composite membranes (PFSA/PPSU) versus using Nafion membranes. The Rh x S y electrocatalyst proved to be more stable in the presence of HBr/Br 2 than pure Pt. However, the H 2 oxidation activity on Rh x S y is quite low compared to that of Pt. In conclusion, a stable H 2 electrocatalyst that can match the hydrogen oxidation activity obtained with Pt and a membrane with low Br 2 /Br − permeability are essential to prolong the lifetime of a H 2 -Br 2 fuel cell. Electrochemical energy storage using flow batteries or reversible fuel cell devices are considered feasible options for taking advantage of renewable energy sources such as wind and solar. [1][2][3][4] An ideal reversible fuel cell should possess qualities such as swift reaction kinetics, inexpensive reactants, high round trip efficiency, and durability. Several research efforts conducted in this area have identified the reversible hydrogen-bromine (H 2 -Br 2 ) fuel cell as a suitable system for large scale electrical energy storage because of its numerous advantages such as rapid Br 2 and H 2 reaction kinetics, low cost ($1-$3 per kg of hydrobromic acid), and relative abundance of the active materials used in this system. [5][6][7][8][9][10][11][12][13] However, the toxicity and corrosivity of the HBr/Br 2 electrolyte used in this system pose major safety and durability challenges that need to be addressed.A conventional H 2 -Br 2 fuel cell consists of a H 2 electrode and a Br 2 electrode separated by a proton exchange membrane. However, microporous membrane and membrane-less versions of several fuel cell systems have been investigated. [13][14][15] Recently, Braff et al. developed a membrane-less version of the H 2 -Br 2 flow battery to reduce the cost and ease the hydration requirements associated with the system. 13The starting material in the H 2 -Br 2 fuel cell system is hydrobromic acid (HBr). With excess energy from either wind or solar, the HBr solution is electrolyzed to form H 2 and Br 2 at their respective electrodes (charge process) and the process is reversed during discharge. Also, the bromide (Br − ) ion in the solution may react with neutral bromine (Br 2 ) species to form a tri-bromide (Br 3 − ) complex....

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Quantitative Correlations between the Normal Incidence Differential Reflectance and the Coverage of Adsorbed Bromide on a Polycrystalline Platinum Rotating Disk Electrode

Abstract: Normal incidence reflectance spectra (λ = 635 nm) data were acquired from a Pt disk of a rotating Pt

Cited by 9 publications

References 24 publications

The Oxidation of Bromide on Platinum Electrodes in Aqueous Acidic Solutions: Electrochemical and In Situ Spectroscopic Studies

The Oxidation of Bromide on Platinum Electrodes in Aqueous Acidic Solutions: Electrochemical and In Situ Spectroscopic Studies

Quantitative In Situ Differential Reflectance Spectroscopy Analysis of Polycrystalline Platinum Oxidation in an Aqueous Acidic Electrolyte

A Comprehensive Study of an Acid-Based Reversible H₂-Br₂Fuel Cell System

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Quantitative Correlations between the Normal Incidence Differential Reflectance and the Coverage of Adsorbed Bromide on a Polycrystalline Platinum Rotating Disk Electrode

Abstract: Normal incidence reflectance spectra (λ = 635 nm) data were acquired from a Pt disk of a rotating Pt

Cited by 9 publications

References 24 publications

The Oxidation of Bromide on Platinum Electrodes in Aqueous Acidic Solutions: Electrochemical and In Situ Spectroscopic Studies

The Oxidation of Bromide on Platinum Electrodes in Aqueous Acidic Solutions: Electrochemical and In Situ Spectroscopic Studies

Quantitative In Situ Differential Reflectance Spectroscopy Analysis of Polycrystalline Platinum Oxidation in an Aqueous Acidic Electrolyte

A Comprehensive Study of an Acid-Based Reversible H2-Br2Fuel Cell System

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A Comprehensive Study of an Acid-Based Reversible H₂-Br₂Fuel Cell System