Oscillations in the emf of solid-state electrochemical oxygen sensors

Hetrick, Robert E.; Logothetis, E. M.

doi:10.1063/1.90577

Cited by 30 publications

(11 citation statements)

References 6 publications

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“…For this molecule in the electronically excited state, the passing over a low activation barrier (-1300 cm-') on the way from the trans-into the 90"-(photochemical funnel) configuration has been investigated energy and time resolved. Isolated molecule conditions were applied in supersonic jets [7][8][9][10] and in low pressure gases [ll - [36] where the rate coefficient in the high density limit should vary inversely proportional to the solvent viscosity. On the other hand, an inverse proportionality of the rate coefficients and the viscosity was nearly fulfilled in polar solvents [22,33].…”

Section: Introductionmentioning

confidence: 99%

Picosecond‐Absorption Study of the Photoisomerization of Trans‐Stilbene in Compressed Gases and Liquids

Maneke

Schroeder

Troe

et al. 1985

Ber Bunsenges Phys Chem

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The photoisomerization of trans‐stilbene after picosecond excitation at 308 nm has been studied by picosecond absorption at 500 or 616 nm in ethane and propane. Experiments were performed in gaseous ethane (30–54 bar), liquid ethane (42–6000 bar), and liquid propane (9–4050 bar). The pressure dependence of the reaction is modelled from isolated molecule conditions in low pressure gases up to diffusion control in high pressure liquids. In dense media marked solvent shifts of the reaction threshold energy are postulated which can be described by simple cluster — and cage — solvent shift models. UV spectra show similar solvent shifts as isomerization rates.

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Section: Introductionmentioning

confidence: 99%

Picosecond‐Absorption Study of the Photoisomerization of Trans‐Stilbene in Compressed Gases and Liquids

Maneke

Schroeder

Troe

et al. 1985

Ber Bunsenges Phys Chem

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“…ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 157.182.150 22. Downloaded on 2015-06-30 to IP…”

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confidence: 98%

Noncatalytic Electrodes for Solid‐Electrolyte Oxygen Sensors

Haaland¹

1980

J. Electrochem. Soc.

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The catalytic effects of various electrode materials on nonequilibrium oxygen measurements using solid-electrolyte oxygen sensors have been investigated. Catalytically active electrodes can perturb the measurement of oxygen in nonequilibrium mixtures of oxygen and combustible gases. This paper reports the development of noncatalytic electrodes for accurate measurement of the free oxygen content in nonequilibrium gas mixtures containing 02 and CH4, CaI-I~, CO, or H2. The effects of Pt, Au, Ag, Ag deposited on Pt, and S-or Pb-poisoned Pt electrodes on the measurement of oxygen in nonequilibrium gas mixtures were determined. These studies were made using solid-electrolyte oxygen sensors of a new internal-reference design as well as with traditional air-reference sensors. Pt electrodes are catalytic in all of the gas mixtures studied. Both Ag electrodes and Ag vapor deposited on Pt were found to be noncatalytic to CH4 oxidation while Au electrodes were only slightly catalytic. Pt electrodes poisoned by S introduced as H~S were also noncatalytic to CH4 oxidation until th e sulfur desorbed at ~800~The above electrodes were sufficiently catalytic to CO oxidation that they could not be used for quantitative nonequilibrium oxygen measurements when CO is present. Pt electrodes poisoned by Pb (introduced as PbS) produced the least perturbation of the nonequilibrium mixtures of oxygen with CH4, Call6, CO, or H2. The Pb-poisoned Pt electrodes allow quantitative measurement of the bulk nonequilibrium oxygen concentrations at temperatures above 500~176 depending on the combustible gas present. At lower temperatures, even the Pb-poisoned electrodes are catalytic. This suggests that Pb may poison the platinum activity by decreasing the heat of adsorption of adsorbed reaction species. Sulfur-or Pb-poisoned Pt or Pt with a thin layer (<200A) of Ag had no adverse effect on the electrochemical O2 pumping capabilities of Pt. Ag and Au electrodes performed poorly as electrochemical O2 pump electrodes. The capability of solid-electrolyte oxygen sensors to measure the partial pressure of gas phase oxygen at the electrode surface was used to investigate the catalytic reaction mechanism of CO oxidation on Pt electrodes partially poisoned by Pb. The results are best fit by an Eley-Rideal mechanism where adsorbed O2 reacts with gas phase CO. However, the data are not sufficiently definitive to rule out the Langmuir-Hinshelwood mechanism where adsorbed O and CO react on the surface. The methods used demonstrate that solid-electrolyte oxygen sensors can be useful experimental tools for identifying catalytic mechanisms.Solid-electrolyte oxygen sensors have been used in a variety of applications for over two decades (1, 2). Almost all applications have either involved the monitoring of oxygen in inert environments or the measurement of equilibrium oxygen in reactive environments. For these purposes, platinum is the electrode material of choice due to its excellent oxygen electrode capabilities (e.g., low polarization) as well as its high catalyt...

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“…The achieved detection sensitivity for oxygen is around ppmv level or even lower in the near infrared region due to the substantially increased pathlength [67,68], which significantly outperforms the detection sensitivity of conventional gas sensors, e.g., the lambda probe [69], luminescence quenching sensors [70], and oxygen phosphorescence [71], and electrochemical methods [72]. However, these techniques use high reflectivity mirrors and need high-finesse optical alignment, which increases the complexity and cost, and thus limits the applications.…”

Section: Pathlength Enhancement—a Random Multipass Gas Cellmentioning

confidence: 99%

Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy

Mei

Somesfalean

Svanberg

2014

Sensors

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Gas in scattering media absorption spectroscopy (GASMAS) has been extensively studied and applied during recent years in, e.g., food packaging, human sinus monitoring, gas diffusion studies, and pharmaceutical tablet characterization. The focus has been on the evaluation of the gas absorption pathlength in porous media, which a priori is unknown due to heavy light scattering. In this paper, three different approaches are summarized. One possibility is to simultaneously monitor another gas with known concentration (e.g., water vapor), the pathlength of which can then be obtained and used for the target gas (e.g., oxygen) to retrieve its concentration. The second approach is to measure the mean optical pathlength or physical pathlength with other methods, including time-of-flight spectroscopy, frequency-modulated light scattering interferometry and the frequency domain photon migration method. By utilizing these methods, an average concentration can be obtained and the porosities of the material are studied. The last method retrieves the gas concentration without knowing its pathlength by analyzing the gas absorption line shape, which depends upon the concentration of buffer gases due to intermolecular collisions. The pathlength enhancement effect due to multiple scattering enables also the use of porous media as multipass gas cells for trace gas monitoring. All these efforts open up a multitude of different applications for the GASMAS technique.

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Oscillations in the emf of solid-state electrochemical oxygen sensors

Cited by 30 publications

References 6 publications

Picosecond‐Absorption Study of the Photoisomerization of Trans‐Stilbene in Compressed Gases and Liquids

Picosecond‐Absorption Study of the Photoisomerization of Trans‐Stilbene in Compressed Gases and Liquids

Noncatalytic Electrodes for Solid‐Electrolyte Oxygen Sensors

Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy

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