Rotating Electrode Methods and Oxygen Reduction Electrocatalysts - Wei Xing, Geping Yin, Jiujun Zhang

Rotating Electrode Methods and Oxygen Reduction Electrocatalysts (eBook)

Wei Xing, Geping Yin, Jiujun Zhang (Autoren)

eBook Download: PDF | EPUB

2014 | 1. Auflage
322 Seiten
Elsevier Science (Verlag)
978-0-444-63328-6 (ISBN)

This book provides the latest information and methodologies of rotating disk electrode and rotating ring-disk electrode (RDE/RRDE) and oxygen reduction reaction (ORR). It is an ideal reference for undergraduate and graduate students, scientists, and engineers who work in the areas of energy, electrochemistry science and technology, fuel cells, and other electrochemical systems.

Presents a comprehensive description, from fundamentals to applications, of catalyzed oxygen reduction reaction and its mechanisms
Portrays a complete description of the RDE (Rotating Disc Electrode)/RRDE (Rotating Ring-Disc Electrode) techniques and their use in evaluating ORR (Oxygen Reduction Reaction) catalysts
Provides working examples along with figures, tables, photos and a comprehensive list of references to help understanding of the principles involved

Dr. Wei Xing is a Professor and Dean at the Advanced Chemical Power Sources, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (CIAC-CAS). Prof. Xing received his PhD in Electrochemistry from CIAC-CAS in 1987, since then, as one of the key senior researchers, he established, and continues to lead the Laboratory of Advanced Power Sources at CIAC-CAS, that develops novel proton exchange membrane fuel cells (PEMFC) catalysts and technologies. His research is mainly concentrated on the R&D of fuel cell technologies including PEMFCs, direct methanol fuel cells (DMFCs), direct formic acid fuel cells (DFAFCs), in which cathode catalyst development for oxygen reduction reaction is the major focus. To date, he has published more than 160 referred journal papers, 3 books, 39 patents. Dr. Xing's research and scientific contributions are internationally recognized.

Rotating Electrode Methods and Oxygen Reduction Electrocatalysts provides the latest information and methodologies of rotating disk electrode and rotating ring-disk electrode (RDE/RRDE) and oxygen reduction reaction (ORR). It is an ideal reference for undergraduate and graduate students, scientists, and engineers who work in the areas of energy, electrochemistry science and technology, fuel cells, and other electrochemical systems. Presents a comprehensive description, from fundamentals to applications, of catalyzed oxygen reduction reaction and its mechanisms Portrays a complete description of the RDE (Rotating Disc Electrode)/RRDE (Rotating Ring-Disc Electrode) techniques and their use in evaluating ORR (Oxygen Reduction Reaction) catalysts Provides working examples along with figures, tables, photos and a comprehensive list of references to help understanding of the principles involved

Electrode Kinetics of Electron-Transfer Reaction and Reactant Transport in Electrolyte Solution

WeiweiCaia,bXiaoZhaoa,bChangpengLiubWeiXingaJiujunZhangc aState Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Changchun, PR China bLaboratory of Advanced Power Sources, Changchun Institute of Applied Chemistry, Changchun, PR China cEnergy, Mining and Environment, National Research Council of Canada, Vancouver, BC, Canada

Abstract

In this chapter, to facilitate understanding and preparing the basic knowledge for rotating electrode theory, both the electron-transfer and reactant transport theories at the interface of electrode/electrolyte are presented. Regarding the reactant transport, three transportation modes such as diffusion, migration, and convection are described. A focusing discussion is given to the reactant diffusion near the electrode surface using both Fick's first and second laws. In addition, based on the approach in literature, the kinetics of reactant transport near and within a porous matrix electrode layer and its effect on the electron-transfer process is also presented using a simple equivalent electrode/electrolyte interface.

Keyword

Electrolyte solutionElectrochemical theoryElectrode reaction kineticsMass-transfer processOxygen reduction reaction (ORR)Oxygen solubilityRotating disk electrode (RDE)Rotating ring-disk electrode (RRDE)

Chapter Outline

2.1. Introduction?34

2.2. Kinetics of Electrode Electron-Transfer Reaction?34

2.2.1. Fundamental Chemical Reaction Kinetics?34

2.2.2. Fundamentals of Electrode Reactions (Bulter–Volmer Equation)?35

2.3. Kinetics of Reactant Mass Transport Near Electrode Surface?44

2.3.1. Three Types of Reactant Transport in Electrolyte (Diffusion, Convection, and Migration)?45

2.3.2. Nonsteady-State Diffusion Process of Reactant when the Electrolyte Solution at the Static State?48

2.3.3. Steady-State Diffusion–Convection Process of Reactant?54

2.4. Effect of Reactant Transport on the Electrode Kinetics of Electron-Transfer Reaction?57

2.4.1. Effect of Reactant Transport on the Kinetics of Electron-Transfer Process?57

2.4.2. Effect of Reactant Transport on the Thermodynamics of Electrode Reaction?59

2.5. Kinetics of Reactant Transport Near and within Porous Matrix Electrode Layer?61

2.6. Chapter Summary?64

References?64

Introduction

The current density measured from the rotating electrode is contributed by both the current densities of electrode electron-transfer reaction and the reactant diffusion. In order to obtain the kinetic parameters of these two processes and their associated reaction mechanisms based on the experiment data, both the theories of electrode electron-transfer reaction and reactant diffusion should be studied and understood. In this chapter, the general theories for electrode kinetics of electron-transfer reaction and reactant diffusion will be given in a detailed level, and we hope these theories will form a solid knowledge for a continuing study in the following chapters of this book.

Kinetics of Electrode Electron-Transfer Reaction

Electrochemical (or electrode) reaction kinetics is one kind of the chemical reaction kinetics. To obtain a better understanding of the theory of electrode reaction kinetics, understanding the basic knowledge of chemical reaction kinetics is necessary. In this section, the general chemical reaction kinetics will be presented first for facilitating the fundamental understanding of electrode kinetics and mechanism, particularly, for oxygen reduction reaction (ORR).

Fundamental Chemical Reaction Kinetics

Consider two substances, A and B, which are linked by simple unimolecular elementary reactions:

?kbkfB

(2-I)

Both elementary reactions at two different directions are active at all times, and the rate of the forward process, vf (mol cm?3 s?1), is

f=kfCA

(2.1)

whereas the rate of the reverse reaction is

b=kbCB

(2.2)

In Eqns (2.1) and (2.2), CA and CB are the concentrations of Substances A and B with a unit of mol cm?3 or M, kf and kb are the reaction rate constants (unit: s?1) for Reactions (2.1) and (2.2), respectively. The net reaction rate (vnet) of A to B is:

net=kfCA?kbCB

(2.3)

At vnet = 0, the net reaction rate is zero; then

fkb=K=CBCA

(2.4)

where K is the equilibrium constant. Equation (2.4) indicates that the kinetics must collapse to relations of the thermodynamic form when reaction time goes to unlimited, otherwise the kinetic picture cannot be accurate. Therefore, Eqn (2.4) is only valid at the state of equilibrium, or a case predicted by reaction thermodynamics. Due to the limitation of reaction time period, it is not easy for a reaction to reach its equilibrium state unless the reaction rates for both directions are extremely high. Therefore, in the study of chemical kinetics, all cases of equilibrium are assumed based on the error tolerance.

Fundamentals of Electrode Reactions (Bulter–Volmer Equation)1

To discuss some basic concepts about the electron-transfer kinetics of electrochemical systems, here we present a simple model reaction as shown in Reaction (4-II).

+n?e??kbkfR

(2-II)

where O and R represent the oxidant and reductant, respectively; n? is the electron-transfer number; kf and kb are the forward and backward reaction rates, respectively. Note that this Reaction (2-II) is an elementary reaction. We use n? to distinguish the electron-transfer number in a simple elementary reaction from that of overall electron-transfer number (n) in a complex reaction such as ORR. For an electrochemical reaction, its reaction mechanism may consist of several such elementary reactions, among which there should be one such elementary reaction as the reaction rate-determining step. The value of n? is normally 1, and for some special cases, it could be 2. For introducing the concept of electrode reaction kinetics, we will focus on such an elementary reaction in this chapter.

As shown in Figure 2.1, due to the electron-transfer reaction occuring on the electrode surface, only those oxidant species with a concentration of CO(0,t) and reductant species with a concentration of CR(0,t) on the electrode surface can participate in the reaction. The oxidant species with a concentration of CO(x,t) and reductant species with a concentration of CR(x,t) in the bulk solution have to diffuse to the electrode surface in order to participate the reaction (note that in both these concentration expressions, t is the reaction time). Therefore, there are basically two processes during the reaction: one is the electron-transfer reaction at the electrode/electrode interface, and that other is the reactant diffusion from a bulk solution to the electrode surface. In this section, we will only discuss the former process, that is, the kinetics of electron-transfer process. The reactant diffusion kinetics will be discussed in the latter section of this chapter.

Figure 2.1Schematic of the electrode electron-transfer and reactant diffusion process in an electrochemical system.CO(0,t) is the surface concentration of oxidant species, CR(0,t) is the surface concentration of reductant species, CO(x,t) is the bulk solution concentration of oxidant, and CR(x,t) is the bulk solution concentration of reductant species. In these four expressions of concentration, t is the reaction time. (For color version of this figure, the reader is referred to the online version of this book.)

The forward and backward reaction rates (?f and ?b, respectively) for Reaction (2-II) can be expressed...

Erscheint lt. Verlag	26.3.2014
Sprache	englisch
Themenwelt	Naturwissenschaften ► Chemie ► Physikalische Chemie
	Naturwissenschaften ► Chemie ► Technische Chemie
	Technik ► Elektrotechnik / Energietechnik
	Technik ► Umwelttechnik / Biotechnologie
ISBN-10	0-444-63328-6 / 0444633286
ISBN-13	978-0-444-63328-6 / 9780444633286

Haben Sie eine Frage zum Produkt?

PDF (Adobe DRM)
Größe: 18,9 MB

Kopierschutz: Adobe-DRM
Adobe-DRM ist ein Kopierschutz, der das eBook vor Mißbrauch schützen soll. Dabei wird das eBook bereits beim Download auf Ihre persönliche Adobe-ID autorisiert. Lesen können Sie das eBook dann nur auf den Geräten, welche ebenfalls auf Ihre Adobe-ID registriert sind.
Details zum Adobe-DRM

Dateiformat: PDF (Portable Document Format)
Mit einem festen Seitenlayout eignet sich die PDF besonders für Fachbücher mit Spalten, Tabellen und Abbildungen. Eine PDF kann auf fast allen Geräten angezeigt werden, ist aber für kleine Displays (Smartphone, eReader) nur eingeschränkt geeignet.

Systemvoraussetzungen:
PC/Mac: Mit einem PC oder Mac können Sie dieses eBook lesen. Sie benötigen eine Adobe-ID und die Software Adobe Digital Editions (kostenlos). Von der Benutzung der OverDrive Media Console raten wir Ihnen ab. Erfahrungsgemäß treten hier gehäuft Probleme mit dem Adobe DRM auf.
eReader: Dieses eBook kann mit (fast) allen eBook-Readern gelesen werden. Mit dem amazon-Kindle ist es aber nicht kompatibel.
Smartphone/Tablet: Egal ob Apple oder Android, dieses eBook können Sie lesen. Sie benötigen eine Adobe-ID sowie eine kostenlose App.
Geräteliste und zusätzliche Hinweise

Buying eBooks from abroad
For tax law reasons we can sell eBooks just within Germany and Switzerland. Regrettably we cannot fulfill eBook-orders from other countries.

EPUB (Adobe DRM)
Größe: 14,6 MB

Dateiformat: EPUB (Electronic Publication)
EPUB ist ein offener Standard für eBooks und eignet sich besonders zur Darstellung von Belletristik und Sachbüchern. Der Fließtext wird dynamisch an die Display- und Schriftgröße angepasst. Auch für mobile Lesegeräte ist EPUB daher gut geeignet.

Buying eBooks from abroad
For tax law reasons we can sell eBooks just within Germany and Switzerland. Regrettably we cannot fulfill eBook-orders from other countries.

Print-Ausgabe

Buch | Hardcover

159,60 €