Platinum Channel Research Articles

Numerical investigation of Catalytic Combustion of Methane Using Wall Surface Reactions

Catalyzed combustion is a low-temperature, flameless process that emits less nitrogen oxide. Italso specifies flammability limits and reactor design constraints. Catalyzed combustion's advantagesdetermine its potential applications. We present a numerical analysis of the catalyzed combustion of amethane-air mixture on a heated platinum channel wall. The cylindrical channel is modeled with 2Daxisymmetric solver. The modeling is based on the “Species transport. The finite volume calculation codeFluent was used to create the various numerical simulations. Interesting findings have been made regardingtemperature and the mass fractions of the various species involved in combustion, including methane(CH4), carbon dioxide (CO2), water (H2O), and nitrogen monoxide (NO) as sources of pollution issues.

Methods to improve electro kinetic energy conversion efficiency in nanoscale channel

With the help of MD simulation in a Lennard jones system, Argon fluid flowing through a Platinum channel, we have demonstrated a practical approach to tune slip length in nanoscale flows. It was found that the presence of solid obstacles in the channel can manipulate the slip length similar to the variation of slip length with respect to fluid solid interaction potential. These results can act as a guidance to improve the electro kinetic energy conversion efficiency in nanoscale flows which will have immense application in the development of nanofluidic battery.

Physics Performance of a Low-Luminosity Low Energy Neutrino Factory

We investigate the minimal performance, in terms of beam luminosity and detector size, of a neutrino factory to achieve a competitive physics reach for the determination of the mass hierarchy and the discovery of leptonic CP violation. We find that a low luminosity of 2×10(20) useful muon decays per year and 5 GeV muon energy aimed at a 10 kton magnetized liquid argon detector placed at 1300 km from the source provides a good starting point. This result relies on θ13 being large and assumes that the so-called platinum channel can be used effectively. We find that such a minimal facility would perform significantly better than phase I of the LBNE project and thus could constitute a reasonable step towards a full neutrino factory.

Tau contamination in the platinum channel at neutrino factories

The platinum channel (${\ensuremath{\nu}}_{e}$ or ${\overline{\ensuremath{\nu}}}_{e}$ appearance) has been proposed at neutrino factories as an additional channel that could help in lifting degeneracies and improving sensitivities to neutrino oscillation parameters, viz., ${\ensuremath{\theta}}_{13}$, ${\ensuremath{\delta}}_{CP}$, mass hierarchy, deviation of ${\ensuremath{\theta}}_{23}$ from maximality and its octant. This channel corresponds to ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{e}$ (${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{\nu}}}_{e}$) oscillations of the initial neutrino flux, with the subsequent detection of electrons (positrons) from charged current interactions of the ${\ensuremath{\nu}}_{e}$ (${\overline{\ensuremath{\nu}}}_{e}$) in the detector. For small values of ${\ensuremath{\theta}}_{13}$, the dominant ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ (${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$) oscillation results in this signal being swamped by electrons arising from the leptonic decay of taus produced in charge-current interactions of ${\ensuremath{\nu}}_{\ensuremath{\tau}}$ (${\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$) with the detector. We examine for the first time the role of this tau contamination to the electron events sample and find that it plays a significant role in the platinum channel compared to other channels, not only at high-energy neutrino factories but surprisingly even at low energy neutrino factories. Even when the platinum channel is considered in combination with other channels such as the golden (muon appearance) or muon disappearance channel, the tau contamination results in a loss in precision of the measured parameters.

Neutrino factory superbeam

We discuss the optimization of a neutrino factory for large sin22θ13, where we assume minimum effort on the accelerator side. This implies that we use low muon energies for the price of an optimized detection system. We demonstrate that such a neutrino factory performs excellent if combined with the electron neutrino appearance channel. Instead of the platinum channel operated with the muon neutrinos from the muon decays, we propose to use the initial superbeam from the decaying pions and kaons, which might be utilized at little extra effort. Since we assume out-of-phase bunches arriving at the same detector, we do not require electron charge identification. In addition, we can choose the proton energy such that we obtain a synergistic spectrum peaking at lower energies. We find that both the superbeam and the neutrino factory beam should used at the identical baseline to reduce matter density uncertainties, possibly with the same detector. This effectively makes the configuration a single experiment, which we call “neutrino factory superbeam”. We demonstrate that this experiment outperforms a low-energy neutrino factory or a wide band beam alone beyond a simple addition of statistics.

Qualitative (sunlight) and quantitative (xenon light source) aspects of the photochemistry of [S2W18O62]4− in the presence of electron donors

The photoelectrochemical properties of the polyoxotungstate anion [S2W18O62]4− dissolved in acetonitrite have been surveyed. Qualitative studies revealed that the rate of oxidation of the electron donor in the presence of sunlight correlated well with the voltammetric peak potential for oxidation of the electron donor at a glassy carbon electrode. Quantitative studies on the photooxidation of tetrahydrofuran, dimethylformamide, triphenylphosphine and ferrocene, as detected at a platinum channel electrode in the presence of a xenon light source, were assigned to a CE mechanism. Simulated fits for the proposed mechanism provide estimates of the reaction rates and data are compared with those obtained previously on the basis of a CECE scheme for the molybdenum analogue.

Optimization of a neutrino factory oscillation experiment

We discuss the optimization of a neutrino factory experiment for neutrino oscillation physics in terms of muon energy, baselines, and oscillation channels (gold, silver, platinum). In addition, we study the impact and requirements for detector technology improvements, and we compare the results to beta beams. We find that the optimized neutrino factory has two baselines, one at about 3000 to 5000km, the other at about 7500km (``magic'' baseline). The threshold and energy resolution of the golden channel detector have the most promising optimization potential. This, in turn, could be used to lower the muon energy from about 50GeV to about 20GeV. Furthermore, the inclusion of electron neutrino appearance with charge identification (platinum channel) could help for large values of \sin^2 2 \theta_{13}. Though tau neutrino appearance with charge identification (silver channel) helps, in principle, to resolve degeneracies for intermediate \sin^2 2 \theta_{13}, we find that alternative strategies may be more feasible in this parameter range. As far as matter density uncertainties are concerned, we demonstrate that their impact can be reduced by the combination of different baselines and channels. Finally, in comparison to beta beams and other alternative technologies, we clearly can establish a superior performance for a neutrino factory in the case \sin^2 2 \theta_{13} < 0.01.

Photoelectrochemistry of bromonitrobenzenes: mechanism and photoelectrochemically-induced halex reactions

The theory for homogeneous EC revE, EC revCE and ECECE mechanisms at macroscopically large channel electrodes is derived. The photoelectrochemical reductions of para-bromonitrobenzene and 2,4-dibromonitrobenzene in acetonitrile solutions and at macroscopic platinum channel electrodes are studied using irradiation at 330 and 470 nm, corresponding to absorption bands in the corresponding radical anions. The former compound is shown to follow a homogeneous EC revCE pathway in acetonitrile solutions containing tetrabutylammonium-based supporting electrolytes; by changing the supporting electrolyte to a salt of the tetramethylammonium cation, the mechanism is changed qualitatively and follows an ECEE pathway. The photoelectrochemical reduction of 2,4-dibromonitrobenzene in acetonitrile solution containing supporting electrolytes derived from the tetrabutylammonium cation is shown to follow an overall ECECE mechanism, with both chemical steps being chemically-reversible, and with the loss of the ortho-bromo in the dark. In the presence of chloride supporting electrolytes, it is shown that light-induced rupture of a CBr bond occurs reversibly with the competing formation of a CCl bond. Unoptimised bulk photoelectrosynthesis indicates that some halogen exchange occurs, demonstrating the viability of a novel approach to halex reactions.

Photoelectrochemical Determination of Ascorbic Acid Using Methylene Blue Immobilized in α-Zirconium Phosphate

Photoelectrochemical analysis of ascorbic acid is reported in aqueous solution at a platinum channel electrode using the dissolved pheno- thiazine dyes methylene blue and methylene green. This is achieved by measuring the current produced by immediate electrooxidation of the reduced form of the dyes produced during the 1:1 photoreaction between the dyes and ascorbic acid induced by visible light. This behavior is similar to that reported previously for toluidine blue, and rate constants for the photochemical reaction of 360±20 mol-1 dm3 s–1 for methylene blue and 150±20 mol–1 dm3 s–1 for methylene green are determined using simulation of the observed photocurrent as a function of flow rate. The light used for this determination was at 620–625 nm and came from a monochromated 1000 W xenon arc lamp. The technique is extended to the immobilization of methylene blue in a zirconium phosphate lattice, which has a layer structure. Methylene blue was chosen since it intercalates to the greatest extent as evidenced by the size of new peaks apparent in its powder X-ray pattern. The dye/phosphate compound is mixed with graphite and mineral oil such that there is a 10:1 ratio of dye/phosphate to graphite to produce a viable photo-electrode. It is found that the photoreaction proceeds as in solution and that a light pen (laser pointer) producing 4 mW of light of wavelength 620–670 nm is sufficient to produce significant photocurrents with ascorbic acid which permit the quantitative determination of the latter at concentrations up to 1.0 mM. Finally a prototype sensor design is described, incorporating an all-in-one unit comprising the photo-electrode and light pen together. This is used to measure the amount of ascorbic acid in the commercial headache remedy Resolve. A value of 31.0±1.0 mg per sachet is found, compared with 30 mg/sachet determined independently.

The electrochemical oxidation of cobalt tris(dithiocarbamates) and tris(diselenocarbamates) in acetonitrile; a combined spectroscopic and voltammetric study

Abstract The electrochemical oxidation of cobalt(III) dithiocarbamates and diselenocarbamates (CoL 3 ) in acetonitrile+0.1 M Bu 4 NPF 6 is shown to occur via the mechanism: (E) CoL 3 ↔[CoL 3 ] + +e − ; (C 2 ) 2[CoL 3 ] + →[Co 2 L 5 ] + +oxidized ligand; (C) [Co 2 L 5 ] + +2CH 3 CN→CoL 3 +[CoL 2 (CH 3 CN) 2 ] + . A combination of electrochemical, electrospray mass spectrometry, and 59 Co/ 77 Se NMR experiments confirms that the binuclear species, [Co 2 L 5 ] + , reacts with acetonitrile forming CoL 3 and [CoL 2 (CH 3 CN) 2 ] + . At the electrode surface, CoL 3 species generated by this reaction may then be reoxidised resulting in an enhanced peak or limiting current. Consequently, the oxidation of CoL 3 in acetonitrile represents an overall EC 2 C mechanism. The data obtained from cyclic voltammetry at Pt disc electrodes and steady-state hydrodynamic voltammetry at platinum channel electrodes for oxidation of CoL 3 were modelled according to this EC 2 C scheme using the commercial DigiSim electrochemical simulation package and the backwards implicit finite difference technique, respectively. Good fits between experiment and simulation were obtained using the same kinetic parameters for both methods. The calculated dimerisation rate constant (C 2 step) is similar to the value obtained in dichloromethane, which is uncomplicated by reaction of [Co 2 L 5 ] + with the solvent. It was observed that if either voltammetric technique was used in isolation, a wider range of combinations of kinetic parameters could be utilised in order to obtain satisfactory fits between experiment and theory.

The photoelectrochemical reduction of p-bromo-nitrobenzene: An ECEE, ECE or DISP process? Mechanistic resolution via channel electrode voltammetry

The photoelectrochemical reduction of p-bromo-nitrobenzene in acetonitrile solution, containing tetrabutylammonium perchlorate as supporting electrolyte, was studied using a platinum channel electrode. It is shown that p-bromo-nitrobenzene is reduced at a half-wave potential of −0.98 V (vs. Ag pseudo-reference electrode) to form a radical anion which is stable in the absence of light. On irradiation with light of wavelength 330 nm, corresponding to an absorption band in the radical anion, appreciable photocurrents flow and in situ electrochemical electron spin resonance (ESR) shows the formation of the nitrobenzene radical onion. The mechanism of formation is shown to occur via a “photo-ECE” mechanism rather than either “photo-ECEE” or “photo-DISP” processes by means of (i) the variation in photocurrent with flow rate, and (ii) novel phototransient experiments in which the photocurrent is followed after the step-wise application of light to the system after steady-state transport l imited currents have been established in the dark at various flow rates. Experiments conducted in the presence of different concentrations of added Br − show steady-state photocurrents that are diminished relative to those flowing under corresponding conditions in the absence of added Br −. The kinetic modelling of this effect is consistent with a light-induced breakage of the carbon-bromine bond in the C-step of the ECE process followed by reaction of the ·φNO 2 radical thus formed with both Br − and the solvent system.

Voltammetric monitoring of photochemical reactions: The photosubstitution of group VIA hexacarbonyls

AbstractVoltammetry at an irradiated platinum channel electrode is used to monitor photosubstitution reactions of the Group VIA hexacarbonyls, M(CO)6 (M = Cr,Mo,W), in acetonitrile solution, in which up to three CO ligands are replaced by solvent molecules. It is shown that this methodological approach can be used to suggest reaction mechanisms and to quantify rates of photoreactions, so giving estimates of quantum yields.

Organometallic photoelectrochemistry: the photo-oxidation of an (arene)chromium tricarbonyl system

The photoelectrochemical oxidation of the compound tricarbonyl(N,N,N′,N′-tetramethyl-1,4- phenylenediamine)chromium 1, has been studied using a platinum channel electrode. Maximum photocurrents are seen at an irradiation wavelength of 365 nm corresponding to a metal-to-ligand charge transfer absorption. By means of in situ electrochemical EPR and quantitative photocurrent/mass transport measurements the process is shown to be of the photo-CE type and a rate constant and approximate quantum yield are reported.