Stimulation Electrodes Based on MnO2 Thin Films: Electrical Properties in Carbonate Buffered Saline

1985 ◽  
Vol 55 ◽  
Author(s):  
Ellen M. Kelliher ◽  
Timothy L. Rose
Keyword(s):  
Manganese Dioxide ◽  
Active Surface ◽  
Alkaline Solutions ◽  
Manganese Acetate ◽  
Proton Diffusion ◽  
Rate Determining Step ◽  
Solid Film ◽  
Image Position ◽  
Saline Solutions ◽  
Kinetics Of

ABSTRACTHydrous manganese dioxide films are being investigated as a new redox material for the active surface of intracortical stimulation electrodes. The films are electrodeposited at room temperature on Pt substrates from a neutral solution of manganese acetate. The electrochemical properties of the films have been evaluated by cyclic voltammetry in neutral saline solutions buffered with bicarbonate. The films undergo a reversible charge injection reaction represented asThe results obtained in electrolytes of different buffer concentrations indicate the film is able to store the most charge in solutions having the lowest buffer capacity. The kinetics of the redox reaction thus favor operation in an acidic or basic environment in agreement with earlier published results. Two different mechanisms are proposed to explain the rate enhancement at the different pH's. In acidic electrolytes the reaction proceeds by dissolution of the film, while in alkaline solutions the rate determining step of proton diffusion in the solid film is increased. For neural stimulation, therefore, electrodes with manganese dioxide films should be pulsed cathodically to insure a neutral or alkaline environment around the electrode and minimize dissolution of the film.

Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

scholarly journals Single entity electrochemistry and the electron transfer kinetics of hydrazine oxidation

Nano Research ◽  
2021 ◽  
Author(s):  
Ruiyang Miao ◽  
Lidong Shao ◽  
Richard G. Compton
Keyword(s):  
Electron Transfer ◽  
Bulk Solution ◽  
Relative Contribution ◽  
Rate Determining Step ◽  
Multistep Process ◽  
Ph Range ◽  
Electro Catalytic Oxidation ◽  
Single Particle Impact ◽  
The Impact ◽  
Kinetics Of

AbstractThe mechanism and kinetics of the electro-catalytic oxidation of hydrazine by graphene oxide platelets randomly decorated with palladium nanoparticles are deduced using single particle impact electrochemical measurements in buffered aqueous solutions across the pH range 2–11. Both hydrazine, N2H4, and protonated hydrazine N2H5+ are shown to be electroactive following Butler-Volmer kinetics, of which the relative contribution is strongly pH-dependent. The negligible interconversion between N2H4 and N2H5+ due to the sufficiently short timescale of the impact voltammetry, allows the analysis of the two electron transfer rates from impact signals thus reflecting the composition of the bulk solution at the pH in question. In this way the rate determining step in the oxidation of each specie is deduced to be a one electron step in which no protons are released and so likely corresponds to the initial formation of a very short-lived radical cation either in solution or adsorbed on the platelet. Overall the work establishes a generic method for the elucidation of the rate determining electron transfer in a multistep process free from any complexity imposed by preceding or following chemical reactions which occur on the timescale of conventional voltammetry.

Hollow structure engineering of FeCo alloy nanoparticles electrospun in nitrogen-doped carbon enables high performance flexible all-solid-state zinc–air batteries

2020 ◽  
Vol 4 (4) ◽  
pp. 1747-1753 ◽  
Author(s):  
Yuanyuan Ma ◽  
Wenjie Zang ◽  
Afriyanti Sumboja ◽  
Lu Mao ◽  
Ximeng Liu ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Hollow Structure ◽  
Active Surface ◽  
Oxygen Electrode ◽  
Active Surface Area ◽  
Active Components ◽  
Nitrogen Doped Carbon ◽  
Structure Engineering ◽  
Kinetics Of

Hollow structuring of active components is an effective strategy to improve the kinetics of oxygen electrode catalysts, arising from the increased the active surface area, the defects on the exposed surface, and the accessible active sites.

Kinetics of reactions of Ni contact pads with Si nanowires

2011 ◽  
Vol 26 (17) ◽  
pp. 2282-2285 ◽  
Author(s):  
Nicholas S. Dellas ◽  
Michael Abraham ◽  
Sharis Minassian ◽  
Chito Kendrick ◽  
Suzanne E. Mohney
Keyword(s):  
Si Nanowires ◽  
Image Position ◽  
Kinetics Of

Abstract

scholarly journals The kinetics of the hydrogen chloride oxidation

2013 ◽  
Vol 78 (12) ◽  
pp. 2115-2130 ◽  
Author(s):  
Martinez Gonzalez ◽  
Tanja Vidakovic-Koch ◽  
Rafael Kuwertz ◽  
Ulrich Kunz ◽  
Thomas Turek ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Gas Phase ◽  
Hydrogen Chloride ◽  
Reaction Order ◽  
Membrane Electrode ◽  
Polarization Data ◽  
Rate Determining Step ◽  
Electrode Assemblies ◽  
Apparent Kinetic Parameters ◽  
Kinetics Of

Hydrogen chloride (HCl) oxidation has been investigated on technical membrane electrode assemblies in a cyclone flow cell. Influence of Nafion loading, temperature and hydrogen chloride mole fraction in the gas phase has been studied. The apparent kinetic parameters like reaction order with respect to HCl, Tafel slope and activation energy have been determined from polarization data. The apparent kinetic parameters suggest that the recombination of adsorbed Cl intermediate is the rate determining step.

scholarly journals A Labile Metallo-Porphyrin as Tool to Control J-Aggregates Chiroptical Properties

2020 ◽  
Author(s):  
Luigi Monsù Scolaro ◽  
Ilaria Occhiuto ◽  
Mariachiara Trapani ◽  
ROBERTO ZAGAMI ◽  
Andrea Romeo ◽  
...  
Keyword(s):  
Dipolar Coupling ◽  
Initial Conditions ◽  
Coupling Mechanism ◽  
Precise Control ◽  
Rate Determining Step ◽  
Initial Nucleus ◽  
Acidic Conditions ◽  
J Aggregates ◽  
Kinetics Of ◽  
Autocatalytic Growth

The zinc(II) metal derivative of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4) is quite labile and readily demetallates under acidic conditions, affording the parent diacid porphyrin in a monomeric form. The rate of this process is first order on [ZnTPPS4] and second order on [H+], allowing a precise control of the monomer release in solution. Under high ionic strength, this latter species is able to self-assemble into J-aggregates, whose kinetics of growth are largely modulated by pH. The aggregation kinetics have been treated according to a well-established model, in which the formation of an initial nucleus is the rate determining step preceding the autocatalytic growth of the whole assembly. The extinction spectra of the aggregates suggest the occurrence of a dipolar coupling mechanism very similar to that operating in metal nanoparticles. Spontaneous symmetry breaking takes place in these aggregates as evidenced by unusual circular dichroism spectra. The intensity and sign of the effect is controlled by the aggregation rate and therefore can be tuned through a proper choice of initial conditions.

The effects of salinity, pH and temperature on the half-life and longevity of Echinostoma caproni miracidia

1998 ◽  
Vol 72 (4) ◽  
pp. 325-330 ◽  
Author(s):  
D.M. Ford ◽  
P.M. Nollen ◽  
M.A. Romano
Keyword(s):  
Life Span ◽  
Half Life ◽  
Alkaline Solutions ◽  
Acid Solutions ◽  
Maximum Life Span ◽  
Echinostoma Caproni ◽  
Ambient Temperatures ◽  
Opposite Trend ◽  
Aquarium Water ◽  
Saline Solutions

AbstractMiracidia of Echinostoma caproni were exposed to solutions varying in salinity, pH, and temperature in 1 ml concavity slides. Half-lives of the miracidial populations were determined and longevity curves constructed to find maximum life spans of the miracidia in the different conditions. Control miracidia in aquarium water at pH 7.2 and 22°C. had a half-life of 3.6 h and a maximum life span of 9 h. Miracidia of E. caproni were not very tolerant of saline solutions from 0.1% to 0.4%, the latter being lethal within an hour. A bimodal effect was found with exposure to aquarium water of varying pH, with a peak at pH 5 in acid solutions and pH 9 in alkaline solutions. Miracidia tolerated pH ranges from 3 to 11 exhibiting half-lives of 2.4 h or greater in these solutions. At lower than ambient temperatures, E. caproni miracidia lived longer, the greatest being a half-life of 5.0 h and a maximum life span of 15h at 5°C. At warmer temperatures, the half-life was reduced until lethality was reached at 40°C. ANCOVA analysis of log transformed longevity curves supported the observation that in pH trials many miracidia survived initially with a major die-off after 3.3 h. The opposite trend of early die-off and gradual mortality of the survivors was supported in the temperature trials.

Kinetic Assessment of the Dry Reforming of Methane over a Solid Solution Ni–La Oxide Catalyst

2021 ◽  
Author(s):  
Victor Stivenson Sandoval-Bohorquez ◽  
Edgar M. Morales-Valencia ◽  
Carlos Omar Castillo-Araiza ◽  
Luz Marina Ballesteros Rueda ◽  
Víctor Gabriel Baldovino Medrano
Keyword(s):  
Solid Solution ◽  
Active Sites ◽  
Oxide Catalyst ◽  
Bond Cleavage ◽  
Scale Up ◽  
Active Surface ◽  
Dry Reforming ◽  
Dry Reforming Of Methane ◽  
Nickel Surface ◽  
Kinetics Of

The dry reforming of methane is a promising technology for the abatement of CH<sub>4</sub> and CO<sub>2</sub>. Solid solution Ni–La oxide catalysts are characterized by their long–term stability (100h) when tested at full conversion. The kinetics of dry reforming over this type of catalysts has been studied using both power law and Langmuir–Hinshelwood based approaches. However, these studies typically deal with fitting the net CH<sub>4</sub> rate hence disregarding competing and parallel surface processes and the different possible configurations of the active surface. In this work, we synthesized a solid solution Ni–La oxide catalyst and tested six Langmuir–Hinshelwood mechanisms considering both single and dual active sites for assessing the kinetics of dry reforming and the competing reverse water gas shift reaction and investigated the performance of the derived kinetic models. In doing this, it was found that: (1) all the net rates were better fitted by a single–site model that considered that the first C–H bond cleavage in methane occurred over a <a>metal−oxygen </a>pair site; (2) this model predicted the existence of a nearly saturated nickel surface with chemisorbed oxygen adatoms derived from the dissociation of CO<sub>2</sub>; (3) the dissociation of CO<sub>2</sub> can either be an inhibitory or an irrelevant step, and it can also modify the apparent activation energy for CH<sub>4</sub> activation. These findings contribute to a better understanding of the dry reforming reaction's kinetics and provide a robust kinetic model for the design and scale–up of the process.

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