Experimental Study of An A+B→C Reaction-Diffusion System in a Capillary: Crossovers from Reaction to Diffusion-Limited Regimes

AbstractContinuing work on elementary A+B→C reactions in capillaries, we study the reaction front dynamics of xylanol orange with Cr3+ in an effectively one-dimentional system with initially separated reactants. This reaction, in contrast to previously studied systems, is not strictly in the diffusion limited regime. i.e. the probability of reaction between species is not unity. Anamalous behavior not seen in the diffusion-limited case has been observed experimentally for the reaction rate, boundary motion, reaction zone width, and local reaction rate. The observed behavior is consistent with recent theoretical studies.

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Study of an A+2B--->C Reaction-Diffusion System with Initially Separated Components

MRS Proceedings ◽

10.1557/proc-366-319 ◽

1994 ◽

Vol 366 ◽

Author(s):

Andrew Yen ◽

Raoul Kopelman

Keyword(s):

Reaction Front ◽

Reaction Rate ◽

Reaction Diffusion ◽

Biological Processes ◽

Local Production ◽

Kinetic Behavior ◽

Acetate Trihydrate ◽

Physical Chemical ◽

Global Reaction ◽

Front Dynamics

ABSTRACTThe presence of a reaction front is a characteristic feature of a variety of physical, chemical and biological processes. A chemical reaction exhibits a front (spatially localized region where concentration of product is non zero), provided the diffusing reactants are separated in space. We study the reaction front dynamics of a termolecular A+2B--->C reaction with initially separated components in a capillary. The reaction tetra+2Ni2+--->1:2 complex is used, where ‘tetra’ is disodium ethyl bis(5-tetrazolylazo) acetate trihydrate. We measure and compare with theory the dynamic quantities that characterize the kinetic behavior of the system: the global reaction rate R(t), the location of the reaction center xf(t), the front's width w(t), and the local production rate R(xf,t). The non-classical nature of this dynamical system is confirmed.

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Study of A+B-4C and A+2B–C Reaction-Diffusion System with Initially Separated Components

MRS Proceedings ◽

10.1557/proc-407-119 ◽

1995 ◽

Vol 407 ◽

Author(s):

Andrew Yen ◽

Raoul Kopelman

Keyword(s):

Dynamical System ◽

Reaction Front ◽

Reaction Rate ◽

Reaction Diffusion ◽

Biological Processes ◽

Local Production ◽

Kinetic Behavior ◽

Physical Chemical ◽

Global Reaction ◽

Front Dynamics

ABSTRACTThe presence of a reaction front is a characteristic feature of a variety of physical, chemical and biological processes. The reaction exhibits a front, provided that the diffusing reactants are separated in space. We study the reaction front dynamics of both A+B→C bimolecular and A+2B→C termolecular reactions with initially separated components in a capillary. We measure and compare with theory and simulations the dynamic quantities that characterize the kinetic behavior of the system: the global reaction rate R(t), the location of the reaction center xf(t), the front's width w(t), and the local production rate R(xft). The non-classical nature of this dynamical system is confirmed.

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REACTION-FRONT DYNAMICS IN A+B→C WITH INITIALLY-SEPARATED REACTANTS

Fractals ◽

10.1142/s0218348x93000423 ◽

1993 ◽

Vol 01 (03) ◽

pp. 405-415 ◽

Cited By ~ 8

Author(s):

S. HAVLIN ◽

M. ARAUJO ◽

H. LARRALDE ◽

A. SHEHTER ◽

H.E. STANLEY

Keyword(s):

Reaction Front ◽

Reaction Rate ◽

Reaction System ◽

Diffusion Reaction ◽

Dimensional System ◽

Scaling Exponent ◽

One Dimensional ◽

Recent Developments ◽

The One ◽

Front Dynamics

We review recent developments in the study of the diffusion reaction system of the type A+B→C in which the reactants are initially separated. We consider the case where the A and B particles are initially placed uniformly in Euclidean space at x>0 and x<0 respectively. We find that whereas for d≥2 a single scaling exponent characterizes the width of the reaction zone, a multiscaling approach is needed to describe the one-dimensional system. We also present analytical and numerical results for the reaction rate on fractals and percolation systems.

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Experimental Study of a Reaction-Diffusion System in a Capillary: Complex Behavior of a Seemingly Simple System

MRS Proceedings ◽

10.1557/proc-366-389 ◽

1994 ◽

Vol 366 ◽

Author(s):

Anna Lin ◽

Andrew Yen ◽

Yong-Eun Koo ◽

Raoul Kopelman

Keyword(s):

Reaction Front ◽

Reaction Rate ◽

Capillary Tube ◽

Xylenol Orange ◽

Reaction Diffusion ◽

Reaction Diffusion System ◽

Diffusion System ◽

Product Concentration ◽

Global Rate ◽

Global Reaction

ABSTRACTWe study a reaction-diffusion system within the confines of a thin capillary tube. Xylenol orange and Cr 3+ are introduced into a capillary tube from opposite ends and meet in the middle forming a reaction front. Unequal initial concentrations of the reactants causes the center of the reaction front to move in time. Characteristics of the front such as the width of the reaction zone, w, the position of the center of the front, xf, the global reaction rate, R, and the local reaction rate, r(xf,t) are determined by continuously monitoring the product concentration in space vs. time. We observe crossover of the global rate from classical to non-classical behavior and a splitting of the reaction front.

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Modeling the Electrical Double Layer to Understand the Reaction Environment in a CO2 Electrocatalytic System

10.26434/chemrxiv.9206075.v1 ◽

2019 ◽

Author(s):

Divya Bohra ◽

Jehanzeb Chaudhry ◽

Thomas Burdyny ◽

Evgeny Pidko ◽

wilson smith

Keyword(s):

Electric Field ◽

Double Layer ◽

Electrical Double Layer ◽

Surface Reaction ◽

Catalyst Surface ◽

Local Reaction ◽

Reaction Diffusion ◽

Alkali Metal Cations ◽

Applied Potential ◽

Critical Aspect

The environment of a CO2 electroreduction (CO2ER) catalyst is intimately coupled with the surface reaction energetics and is therefore a critical aspect of the overall system performance. The immediate reaction environment of the electrocatalyst constitutes the electrical double layer (EDL) which extends a few nanometers into the electrolyte and screens the surface charge density. In this study, we resolve the species concentrations and potential profiles in the EDL of a CO2ER system by self-consistently solving the migration, diffusion and reaction phenomena using the generalized modified Poisson-Nernst-Planck (GMPNP) equations which include the effect of volume exclusion due to the solvated size of solution species. We demonstrate that the concentration of solvated cations builds at the outer Helmholtz plane (OHP) with increasing applied potential until the steric limit is reached. The formation of the EDL is expected to have important consequences for the transport of the CO2 molecule to the catalyst surface. The electric field in the EDL diminishes the pH in the first 5 nm from the OHP, with an accumulation of protons and a concomitant depletion of hydroxide ions. This is a considerable departure from the results obtained using reaction-diffusion models where migration is ignored. Finally, we use the GMPNP model to compare the nature of the EDL for different alkali metal cations to show the effect of solvated size and polarization of water on the resultant electric field. Our results establish the significance of the EDL and electrostatic forces in defining the local reaction environment of CO2 electrocatalysts.

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Reaction-diffusion master equation, diffusion-limited reactions, and singular potentials

Physical Review E ◽

10.1103/physreve.80.066106 ◽

2009 ◽

Vol 80 (6) ◽

Cited By ~ 29

Author(s):

Samuel A. Isaacson ◽

David Isaacson

Keyword(s):

Master Equation ◽

Reaction Diffusion ◽

Singular Potentials ◽

Diffusion Limited

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Experimental Investigations of the Kinetics of a Catalytic Trapping Reaction in Confined Spaces

MRS Proceedings ◽

10.1557/proc-464-225 ◽

1996 ◽

Vol 464 ◽

Author(s):

Mark S. Feldman ◽

Anna L. Lin ◽

Raoul Kopelman

Keyword(s):

Reaction Front ◽

Rate Coefficient ◽

Capillary Tube ◽

One Dimension ◽

Experimental Investigations ◽

Confined Spaces ◽

Diffusion Limited ◽

Kinetics Of ◽

Oxidation Of Glucose ◽

Theoretical Results

AbstractWe investigate the anomalous kinetics in one dimension of a diffusion limited catalytic trapping reaction, A + T → T, by measuring the oxidation of glucose. The reaction is carried out in a thin capillary tube, and the depletion of oxygen in the vicinity of the reaction front is monitored by the fluorescence of a Ru(II) dye. Theoretical results and simulations have predicted an asymptotic t1/2 dependence for the rate coefficient. We observe a depedence on t0.56, with what appears to be an asymptotic behavior approaching t1/2.

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