Electrochemistry: The Basics, With Examples

367 Pages·2012·9.195 MB·English

by  Christine Lefrou, Pierre Fabry, Jean-Claude Poignet

Electrochemistry
Grenoble Sciences
The aims of Grenoble Sciences are double:
(cid:1) to produce works corresponding to a clearly defined project, without the constraints
of trends or programme,
(cid:1) to ensure the utmost scientific and pedagogic quality of the selected works:
each project is selected by Grenoble Sciences with the help of anonymous referees. In
order to optimize the work, the authors interact for a year (on average) with the mem-
bers of a reading committee, whose names figure in the front pages of the work,
which is then co-published with the most suitable publishing partner.
(Contact: Tel.: [phone] - e-mail: [email protected]
Information: http://grenoble-sciences.ujf-grenoble.fr)
Scientific Director of Grenoble Sciences
Jean BORNAREL, Emeritus Professeur at the Joseph Fourier University, France
Grenoble Sciences is a department of the Joseph Fourier University supported by
the French National Ministry for Higher Education and Research
and the Rhône-Alpes Region.
Electrochemistry - The Basics, with Examples is an improved version of the original book
L’électrochimie - Fondamentaux avec exercices corrigés
by Christine LEFROU, Pierre FABRY and Jean-Claude POIGNET
EDP Sciences, Grenoble Sciences’ collection, 2009, ISBN 978 2 7598 0425 2.
The Reading Committee of the French version included the following members:
(cid:1)Michel CASSIR, Professor - ENSCP, Paris
(cid:1)Renaud CORNUT, PhD - Grenoble INP
(cid:1)Christophe COUDRET, Researcher - CNRS, Toulouse
(cid:1)Guy DENUAULT, Senior lecturer - Southampton University, United Kingdom
(cid:1)Didier DEVILLIERS, Professor - Pierre et Marie Curie University, Paris VI
(cid:1)Bruno FOSSET, Professor - Henri IV High School, Paris
(cid:1)Ricardo NOGUEIRA, Professor - Phelma, Grenoble INP
Translation from original French version performed by
Lauren AYOTTE, Isabel PITMAN and Jean-Claude POIGNET
Typesetted by Centre technique Grenoble Sciences
Cover illustration: Alice GIRAUD
Christine Lefrou • Pierre Fabry • Jean-Claude Poignet
Electrochemistry

The Basics, With Examples
Christine Lefrou Pierre Fabry
LEPMI Meylan
Saint Martin d’Heres Cedex France
France
Jean-Claude Poignet
Saint Martin D’Heres
France
Originally published in French: L’électrochimie - Fondamentaux avec exercices corrigés by Christine
Lefrou, Pierre Fabry and Jean-Claude Poignet, EDP Sciences, Grenoble Sciences’ collection, 2009,
ISBN 978-2-7598-0425-2
ISBN 978-3-642-30249-7 ISBN 978-3-642-30250-3 (eBook)

DOI 10.1007/978-3-642-30250-3

Springer Heidelberg New York Dordrecht London

Library of Congress Control Number: 2012939727

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P
REFACE
The emerging constraints related to energy production, which are already shaking our
economies, will undoubtedly increase. Our societies will not only have to produce the
tens of terawatts of energy they require while resorting less and less to fossil fuels (a fact
that implies that electrical energy will dominate), but will also need to find adequate
ways to use and store the transient electrons thus produced. These are considerable
challenges that our present world is not ready to fulfill with its current technologies.
New technologies will have to be envisioned for the efficient management of the
considerable fluxes required, and to this end, Electrochemistry seems to provide some of
the most promising and versatile approaches. Electrochemistry will be involved in solar
cells, electrolytic cells for the production of hydrogen through water electrolysis or the
reductive recycling of carbon dioxide, supercapacitors and batteries for the storage of
electricity produced intermittently by solar cells and windmills, as well as in the use of
electrons as chemical reagents, and so on. This is a vast program that will require the
dedicated and skilled competence of thousands of researchers and engineers, which is
in stark contrast with the present status of electrochemistry in many industrial countries,
where its main focus is the never-ending fight against corrosion or improvement lead
car batteries.
There will be a requirement for much more knowledgeable and versatile electrochemists
than are currently trained in our universities and engineering schools, which is tanta-
mount to saying that our teaching of electrochemistry must evolve drastically. Indeed,
even if today one can easily foresee the great challenges that electrochemists will face,
nobody can know for sure which sustainable and economically viable solutions will
emerge, be selected and even how they will evolve. But to occur all of this will neces-
sarily be rooted on a deep understanding of the fundamental principles and laws of
electrochemistry. Future electrochemical researchers and engineers will unquestionably
adapt, but this can only happen provided that their knowledge is firmly and confidently
mastered. We should recall the great Michael FARADAY’s answer to the Prime Minister of
his time, who asked him about the purpose of understanding electricity and electro-
magnetism: Sir, I certainly don’t know, but I am sure that within thirty years you will be
taxing its applications. To paraphrase him: Today we do not know how electrochemistry
will solve the great challenges ahead, but we do know that nothing will be possible
without a deep understanding of this science.
Within this context, it is a great pleasure to see the present increasing number of new
electrochemistry textbooks, though sadly many of them continue to be written not to
provide students with a deep understanding, but rather with operational conceptual
recipes; this is certainly handy and useful knowledge, but it is ultimately rooted on sand.
So it is my great pleasure to see that a few colleagues, the authors of this book among
them, have undertaken a deeper pedagogical questioning to produce a new type of
electrochemistry textbook for students in their freshman years.
V
VI ELECTROCHEMISTRY-THEBASICS,WITHEXAMPLES
This book offers new approaches to the teaching of electrochemical concepts,
principles, and applications. It is based on a translation and improvement of a previous
version written by the same authors for French-speaking students, so its efficiency has
already been tested in excellent French universities and engineering schools. In fact,
these new approaches were primarily elaborated and refined by one of the authors
during the electrochemical classes she taught to student engineers of Grenoble INP, one
of the major French educational centers, where electrochemistry is integrated as one of
its major courses.
The rigorous but pedagogical approaches developed in this textbook will unques-
tionably provide its readers with a strong knowledge base. Yet in this case, « rigor » is
not synonymous with « painful » or « nerdy ». Indeed, the original presentation and the
possibility of different reading levels will make this textbook accessible and pleasant to
all, irrespective of their initial level. I have absolutely no doubt that students initiated
and trained through clever use of this book will benefit from sound foundations upon
which they will be able to build up the more specialized knowledge that they will
acquire during either their follow-up studies or scientific careers.
Christian AMATORE, HonFRSC
Membre de l’Académie des Sciences
Délegué à l’Education et à la Formation
F
OREWORD
Electrochemistry is a branch of science that focuses essentially on the interfaces
between materials. Therefore it is also a science that lies at the interface between other
scientific disciplines, namely physics and chemistry. These two disciplines use specific
concepts as well as specialised vocabulary which can sometimes be confused. Today,
with the fast-growing spread of new technologies, specialists from various sectors are
finding themselves increasingly drawn together to collaborate on research and devel-
opment projects, including synthesizing and elaborating materials as well as in areas
such as analysis, the environment and renewable energies. As a consequence, certain
notions need to be clarified to ensure that the interested reader is able to understand,
whatever his or her core education.
Electrochemistry is taught as part of many scientific courses, from basic lessons in
physical chemistry to science for engineers. However, for a long time it was hard to find
books focused exclusively on electrochemistry and its specific concepts, especially in
France. Over the last few decades several textbooks have been published on electro-
chemistry, each of these presenting different yet equally valid approaches. Without
calling into question the overall quality and originality of these texts, there are none-
theless several points in each case which have remained obscure, or even sunk into
oblivion. This could be explained by the ever pressing need to respond to the demands
of the fast-growing field of technology. Whatever the case, it has had serious conse-
quences, namely potentially preventing the scientist from gaining a full understanding
of the subject, and moreover leading to approximations or even errors.
This book owes a lot to the method developed by Christine LEFROU on the university
course that she gives to engineering students at the Grenoble Institute of Technology. It
presents several novel developments as well as helping to bring the reader to a more
profound understanding of the fundamental concepts involved in the different phe-
nomena that occur in an electrochemical cell. Rather than focusing on an in-depth study
of electrode mechanisms (other books give a detailed account of this subject), this book
develops in particular the movement of species in complete electrochemical systems. It
is divided into four chapters, giving a progressive approach. The few redundancies that
might be spotted are therefore not fortuitous and should be viewed as part of a specific
pedagogical method aimed at improving the scientific level in gradual steps.
The authors wish to invite the reader on « a fascinating electrochemical journey between
two electrodes », with the following little piece of advice, in the form of a maxim: the
traveller should know that if he moves too fast, he will miss out on the chance of appreciating
to the full the landscapes he encounters, and he will prevent himself from gaining a proper
understanding of the life and customs of the inhabitants in the land he is exploring...
VII
VIII ELECTROCHEMISTRY-THEBASICS,WITHEXAMPLES
READER GUIDELINES
Here are a few guidelines to help you make the most out of this voyage…
First of all, there are two main reading itineraries to choose from. If you stick to the main
path, then follow the main paragraphs focused on the basic notions. However, if you
take the other path, then you will be going into more rough terrain, exploring the back-
country the paragraphs are written in smaller characters, and the content goes into
more detail, usually giving examples to illustrate the topic. Therefore, these in-depth
paragraphs regularly feature issues which are solved in numerical terms, and can be
seen as a list of applied exercises, laid out in an original fashion (the question is immedi-
ately followed by the solution, including a commentary) so as not to lose the thread.
These exercises and descriptive diagrams often give numerical values that should be
simply viewed as teaching examples. Although the cases covered are plausible in
technical terms, they do not refer to any particular real experimental data.
The appendices give more lengthy and developed calculations, which are not described in
detail elsewhere in the main body of the text. They also provide further reading, which is
kept apart at the end so as not to disrupt the overall pedagogical approach of this book. A
good half of these appendices unveil novel developments and original material that have
never been published before. Throughout the book, the reader can also find numerous
footnotes, comments, added clarifications and cross-references between sections.
The first chapter focuses on the basic notions that need to be mastered before being
able to go on and tackle the following chapters. The reader is reminded of the basic
concepts, all defined in precise detail, as well as being introduced to certain experi-
mental aspects. This chapter is therefore meant more or less for beginners in electro-
chemistry. The common electrochemical systems are described in the second chapter,
which introduces the elementary laws so that they can be applied immediately by the
reader. This chapter does not therefore provide any in-depth demonstrations. However,
it is the last two chapters and the appendices that go into greater depth to tackle the
key notions in a thorough and often original way. The third chapter focuses on aspects
related to thermodynamic equilibrium, and the fourth chapter deals with electro-
chemical devices with a current flow, and which are therefore not in equilibrium.
Summary tables can be found at the end of the book recapping the key features of each
chapter. Finally, in order to give the reader the opportunity to carry out a self-
assessment, each chapter ends with a series of related questions (the answers can be
found at the back of the book).
This book does not aim to give a detailed account of electrochemical applications.
However, certain electrochemical applications are mentioned in illustrated boards in
order to show that the concepts covered are not disconnected from technological
reality. These explanations can be read separately from the core of the text. To find them
in the table of contents, their titles are shaded in and designated by the symbol (cid:1).
Finally, the bibliography indicates the main titles examined by the authors in the course
of writing this book. Therefore, the list is centred on books (both in French and English)
that include a presentation of the fundamental laws of electrochemistry.
FOREWORD IX
ACKNOWLEDGEMENTS
We would like to thank all the people who have helped in working out this book.
First of all, we are indebted to the members of the reading committee for all the care
that they brought to their task. Their suggestions and questions, always delivered with
great tact and modesty, helped to enrich and inspire our work so as to ultimately
improve the content and writing.
Our thanks also go to the members of the Grenoble Sciences editorial team, its director
Jean BORNAREL, and also Laura CAPOLO, Sylvie BORDAGE, Julie RIDARD, Anne-Laure PASSAVANT
and Isabel PITMAN. Their suggestion to include illustrated boards was highly appreciated,
since the result is that they make for more enjoyable reading, and we would like to
express our gratitude to all those who helped compile the content of those illustrated
boards. We also heartily acknowledge the invaluable help of Lauren AYOTTE and Guy
DENUAULT, and their contribution towards improving this work.
Finally, we would like to mention all of the students we have had the pleasure of
working with over the years while developing this project. Although they are too
numerous to be named individually, they equally have all played a role in contributing
to this book. Their questions, as much as their misunderstandings of our lectures as
teachers, have all helped to refine our own thinking, and even shake up our certainties!
The authors