Electrochemical Quartz Crystal Microbalance Study of Borohydride Electro-Oxidation on Pt: The Effect of Borohydride Concentration and Thiourea Adsorption

Lam, V. W. S.; Kannangara, D. C. W.; Alfantazi, Akram; Gyenge, Előd L.

doi:10.1021/jp108771h

Cited by 36 publications

(52 citation statements)

References 51 publications

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“…The magnitude of the relative m decrease is equal to approximately −4.5 × 10 6 ng m −2 for either 20 mM or 60 mM BH 4 − concentrations and is comparable to the response observed on Pt in 60 mM BH 4 − . 6 In the latter case, due to the incomplete oxidation of BH 4 − on Pt there was evidence to suggest that peak C 3 is generated by the oxidation of adsorbed intermediates. 6 In case of Au, the existence of partial oxidation products at the outset of the return scan is less likely because on the anodic scan at high potentials complete oxidation is achieved.…”

Section: Resultsmentioning

confidence: 99%

“…In case of BH 4 − oxidation, EQCM was first employed by the present group using Pt electrode. 6 The goal here was to validate the EQCM technique for the electrooxidation of BH 4 − on the Au.…”

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confidence: 99%

“…However, the complexity of the reaction mechanism and the number of possible faradaic (i.e., involving electron-transfer with the electrode) and nonfaradaic (thermocatalytic) pathways have a significant influence on the anode performance at both open-circuit and under polarization conditions. [1] Most electrode materials that are electrocatalytic toward the borohydride oxidation reaction (such as Pt 5,6 or Ni 7,8 ) possess also thermocatalytic activity for hydrolysis of BH 4 − , generating H 2 and BH 3 OH − (in the first stages) according to: 9 BH − 4 + H 2 O → BH 3 OH − + H 2 .…”

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confidence: 99%

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Borohydride Electro-Oxidation on Gold Investigated by Electrochemical Quartz Crystal Microbalance

Ignaszak

Kannangara

Lam

et al. 2012

J. Electrochem. Soc.

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The quartz crystal microbalance technique coupled with cyclic voltammetry (referred to as electrochemical quartz crystal microbalance (EQCM)) was employed to study the oxidation of BH 4 − on Au in alkaline media (0.1 M and 2 M NaOH, respectively) using a newly designed vertical cell to minimize the interference by evolved H 2 . The electrode potential was scanned between −0.7 and 0.7 V vs. SHE with scan rates in the range of 0.01 V s −1 and 1 V s −1 . The relative mass changes of the Au resonator-electrode were interpreted in combination with density functional theory (DFT) modeling and pertinent experimental results from the literature. The potential scan rate dependent mass change profiles revealed: i) weak adsorption of BH 4 − below −0.2 V leading to high anodic overpotential, ii) accumulation of reaction intermediates on the surface between approximately −0.2 V to 0.3 V (scan rate dependent), and iii) Au surface hydroxide and oxide assisted oxidation of BH 4 − and possibly of other active species present such as BH 3 OH − formed by hydrolysis.Direct borohydride fuel cells have received increased attention over the past decade as potential power source candidates for electronic devices and transportation. 1-4 It is convenient and common to conceptualize the BH 4 − electro-oxidation using Eq. 1. However, the complexity of the reaction mechanism and the number of possible faradaic (i.e., involving electron-transfer with the electrode) and nonfaradaic (thermocatalytic) pathways have a significant influence on the anode performance at both open-circuit and under polarization conditions.Most electrode materials that are electrocatalytic toward the borohydride oxidation reaction (such as Pt 5,6 or Ni 7,8 ) possess also thermocatalytic activity for hydrolysis of BH 4 − , generating H 2 and BH 3 OH − (in the first stages) according to: 9The generation of BH 3 OH − could lower the borohydride utilization efficiency with respect to Eq. 1, by up to about 60%. 10 It was widely accepted in the literature in the past, that Au does not promote the BH 4 − hydrolysis, hence, it is a faradaically efficient eight-electron borohydride oxidation reaction (BOR) catalyst. 5,11 Cheng and Scott have studied the BH 4 − electrooxidation kinetics on Au rotating disk electrode (RDE) and showed that the number of electrons exchanged per BH 4 − anion increases from four at 0.09 V vs. SHE to eight at 0.54 V vs. SHE. 12 Chatenet et al. estimated 7.5 electrons at BH 4 − concentrations lower than 50 mM and proved also the formation of BH 3 OH − at higher concentrations (≥ 50 mM), as the hydrolysis is first order with respect to BH 4 − concentration. 13 Krishnan et al. carried out a detailed analysis using Au rotating ring-disk electrode (RRDE) voltammetry and detected BH 3 OH − on the ring and its further oxidation to BH 2 (OH) 2 − between −0.8 and −0.6 V. They concluded that both the formation and stability of BH 3 OH − is pH dependent and were the first to discuss in depth the BH 4 − hydrolysis on Au. 10 Chatenet et al. in their more recent w...

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Section: Resultsmentioning

confidence: 99%

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Borohydride Electro-Oxidation on Gold Investigated by Electrochemical Quartz Crystal Microbalance

Ignaszak

Kannangara

Lam

et al. 2012

J. Electrochem. Soc.

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“…Cyclic voltammograms performed with the Pt electrode ( Fig. 2a) showed two oxidation waves in the anodic direction, similar to an analogous aqueous system [7]; however the oxidation waves are much broader. The highest BH 4 À oxidation currents and the most negative oxidation onset potential are observed on the oxidized Ni electrode (Fig.…”

Section: Resultsmentioning

confidence: 61%

Borohydride electro-oxidation in a molten alkali hydroxide eutectic mixture and a novel borohydride–periodate battery

Wang

Gyenge

2015

Journal of Power Sources

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“…Experimental and theoretical studies have shown that the electrooxidation of borohydride involves a number of competitive electrocatalytic and thermocatalytic pathways, which can diminish the Faradaic equivalence from eight to four electrons per mol of borohydride converted, depending on the electrocatalyst, electrode potential, temperature, and OH À /BH 4 À ratio. [5][6][7][8][9][10] Gyenge and co-workers demonstrated that osmium nanoparticles are promising candidates as alternatives for platinum electrocatalysts in DBFCs because they cost significantly less and exhibit high catalytic activity for the electrooxidation of borohydride. [9,[11][12][13] DBFC experiments that use an Os/C catalyst-coated Nafion 117 membrane revealed that at 298 K, in both the kinetic and mass-transport regions of the polarization curves, the borohydride electrooxidation on 20 wt % Os/C was superior to commercial 20 wt % Pt/C and Pt-Ru/C.…”

Section: Introductionmentioning

confidence: 99%

Platinum‐ and Membrane‐Free Swiss‐Roll Mixed‐Reactant Alkaline Fuel Cell

2013

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Eliminating the expensive and failure-prone proton exchange membrane (PEM) together with the platinum-based anode and cathode catalysts would significantly reduce the high capital and operating costs of low-temperature (<373 K) fuel cells. We recently introduced the Swiss-roll mixed-reactant fuel cell (SR-MRFC) concept for borohydride-oxygen alkaline fuel cells. We now present advances in anode electrocatalysis for borohydride electrooxidation through the development of osmium nanoparticulate catalysts supported on porous monolithic carbon fiber materials (referred to as an osmium 3D anode). The borohydride-oxygen SR-MRFC operates at 323 K and near atmospheric pressure, generating a peak power density of 1880 W m(-2) in a single-cell configuration by using an osmium-based anode (with an osmium loading of 0.32 mg cm(-2)) and a manganese dioxide gas-diffusion cathode. To the best of our knowledge, 1880 W m(-2) is the highest power density ever reported for a mixed-reactant fuel cell operating under similar conditions. Furthermore, the performance matches the highest reported power densities for conventional dual chamber PEM direct borohydride fuel cells.

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Electrochemical Quartz Crystal Microbalance Study of Borohydride Electro-Oxidation on Pt: The Effect of Borohydride Concentration and Thiourea Adsorption

Cited by 36 publications

References 51 publications

Borohydride Electro-Oxidation on Gold Investigated by Electrochemical Quartz Crystal Microbalance

Borohydride Electro-Oxidation on Gold Investigated by Electrochemical Quartz Crystal Microbalance

Borohydride electro-oxidation in a molten alkali hydroxide eutectic mixture and a novel borohydride–periodate battery

Platinum‐ and Membrane‐Free Swiss‐Roll Mixed‐Reactant Alkaline Fuel Cell

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