Experimental Electrochemistry

A Laboratory Textbook

Rudolf Holze

• Publisher: Wiley-VCH
• Year: 2019
• ISBN:
  9783527676293
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Physical & Theoretical Chemistry

Showing how to apply the theoretical knowledge in practice, the one and only compilation of electrochemical experiments on the market now in a new edition.
Maintaining its didactic approach, this successful textbook provides clear and easy-to-follow instructions for carrying out the experiments, illustrating the most important principles and applications in modern electrochemistry, while pointing out the potential dangers and risks involved.
This second edition contains 84 experiments, many of which cover electrochemical energy conversion and storage as well as electrochemical equilibrium.

1
Introduction: An Overview of Practical Electrochemistry

Students in natural sciences as well as professionals in numerous areas will meet electrochemical methods, concepts, and processes in many fields of science and technology. Accordingly, any conceivable selection of possible experiments intended as an illustration of this width and the numerous possibilities of electrochemistry, and an introduction to the subject has to be similarly broad. According to the book's purpose and intention, this will be achieved by the width of the selection of experiments, the scope of the practical (instrumental) requirements, and the necessary level of knowledge. Convenient use of the book and logical arrangement of the essentials of the theoretical introduction suggest a rational arrangement of experiments. As already proposed and executed elsewhere (R. Holze: Leitfaden der Elektrochemie, Teubner, Stuttgart, 1998 and Elektrochemisches Praktikum, Teubner, Stuttgart, 2000), electrochemistry in equilibrium, that is, without flow of current and conversion of matter, is followed by electrochemistry with flow of current. In the first chapter, measurements of electrode potential and their application in, for example, the determination of thermodynamic data are treated. The second chapter deals with all kinds of experiments where an electrical current crosses the electrochemical interface. Applications of electrochemical methods (both without and with flow of current) are handled in a chapter on electrochemical methods of analytical chemistry.1 This chapter also contains experiments helpful in elucidating, for example, mechanisms of electrode processes (a somewhat broader meaning of analytical) if the focus of the experiment is not on the experimental method itself, thus suggesting its inclusion in one of the preceding chapters. According to the growing impact of nontraditional, in particular spectroscopic, methods in electrochemistry, a small section of experiments from this branch follows; unfortunately, the feasibility of these experiments depends crucially on the presence of mostly expensive instruments. Electrochemical methods of energy conversion and storage are of utmost practical importance, and numerous first personal interactions with electrochemistry deal with these devices. They combine applied aspects of equilibrium (i.e., thermodynamic) electrochemistry and electrochemical kinetics; consequently, in this chapter only those experiments are collected where these aspects are not dominant. Electrochemical methods in industrial (synthetic) chemistry applied in the production of base chemicals, for example, chlorine or sodium hydroxide, and in synthetic procedures are subject of some experiments in the final chapter, the difficulties of the transfer of a large‐scale industrial process into a simple laboratory experiment limit the selection.

The following descriptions of experiments are organized according to a general scheme. A brief statement of the experimenter's task and the aim of the experiment are followed by a condensed description of the theoretical foundations, essentially for understanding the experiment. This information cannot replace the respective parts of a textbook or the original reports in the primary literature. Besides references to primary sources, the respective sections of C.H. Hamann, A. Hamnett, and W. Vielstich, Electrochemistry, Wiley‐VCH Verlag GmbH, Weinheim, 2007, are quoted as EC and the respective page number: EC:xx. Some methods such as polarography and cyclic voltammetry are employed in several experiments; nevertheless, their fundamentals are described only once when the method is introduced first. No attempt is made in the descriptions to list all conceivable applications of the method used in this experiment. The tempting concept to arrange experiments according to difficulty or complexity of the experimental apparatus was discarded soon as being too personal and subjective. Instead, the readers and users of this book will easily select experiments according to their personal interests and intentions; the comparison of available and necessary equipment can subsequently been performed easily as well as the estimate of the required knowledge for successful execution.

The description of the execution of an experiment starts with a list of necessary instruments and chemicals. Possible alternative instrumentations are highlighted; the subsequent description is nevertheless limited to one experimental way only. The description contains – if necessary – a schematic circuit diagram of the setup and sketches of the construction of the apparatus or parts of it. The execution of the suggested measurements is briefly outlined. Potential pitfalls and unusual details are indicated. The way from the raw data to the desired results is sketched. Final questions including those pertaining to the practical execution help to confirm the newly acquired knowledge. Extensive calculation training examples are not included, these can be found in the textbook by J.O'M. Bockris and R.A. Fredlein. Typical results are displayed without cosmetic tidying up, this will encourage the user, it also demonstrates the level of skill needed to obtain satisfactory agreement between literature data (always quoted according to bibliographic standards from generally available textbooks for comparison) and one's own results.

1 Practical Hints

In most experiments aqueous solutions are used. If not stated otherwise, ultrapure water (sometimes called 18 MΩ‐water because of the typical specific resistance value of this water) is used. It can be obtained by after‐purification of deionized water by various commercially available purification systems. As an alternative, doubly distilled (bidistilled) water can be used. In some experiments, simple deionized water can be used. Because especially in demanding conductivity2 and potentiometric measurements, traces of impurities present in deionized water may cause erroneous results, blind tests are required, in particular when water of less than ideal purity is used. In some cases, not only the desired concentration of a necessary solution but also the amount of the selected chemicals needed for preparing the requested amount of solution is given for ease of preparation. When cells or other experimental setups with volumes different from the suggested setup are used, these numbers must obviously be corrected. Purification of organic solvents has been thoroughly described by C.K. Mann (Nonaqueous Solvents for Electrochemical Use, Electroanalytical Chemistry 3 (A.J. Bard, ed.), Marcel Dekker, New York, 1969, p. 57); further information on electrolyte solutions based on organic solvents has been collected by H.J. Gores and J.M.G. Barthel (Pure Appl. Chem., 67 (1995) 919).

1 Electrodes

As suggested by W. Nernst, the term electrode should always be applied to a specific combination of an electronically conducting material (e.g., metal, graphite, semiconductor) and an ionically conducting phase in contact with this material (e.g., an aqueous solution, a polymeric electrolyte, a molten salt). The need for this use will be neatly illustrated in Experiment 3.12 with lead being in contact with various electrolyte solutions; quite obviously, the term lead electrode becomes ambiguous. In daily life, the term electrode mostly refers to the electronically conducting component only. This well‐established usage will not be completely suppressed in this book; nevertheless, the possible confusion will be addressed repeatedly.

In some experiments, electrodes of special shape and construction prepared from selected materials are needed; details are provided in the descriptions of the experiments. In many experiments, electrodes of a fairly general type and construction will be used. Because they can be prepared easily in a glassblower's shop or even without any expert help, some suggestions are given below.

Frequently, metal sheets (of noble metals such as platinum or gold) are used as working and counter electrodes. These electrodes can be manufactured easily by spot welding a metal wire to a piece of sheet metal (about 0.1–0.2 mm thick). After extending the metal wire with a piece of copper wire connected with hard solder (i.e., silver solder; soft solder is not recommended because it will most likely melt in the subsequent glassblowing operation; in addition soft solder forms alloys with gold making a reliable connection impossible), the noble metal wire is sealed into a glass tube. Glass with low melting point is preferred because the low viscosity of the molten glass obtained even at moderate temperatures provides a tight glass–metal seal. With platinum, borosilicate glass of higher melting point can be used. Particularly useful even for silver wires are lead dioxide‐based glasses. The glassblowers must avoid reducing conditions when operating their blowtorch. Unfortunately, these glasses are hard to get. When a spot welding machine is not available, simple metal wire spirals can be used instead of sheet electrodes. Instead, with a glass–metal seal, the wire can also be fixed with epoxy glue; unfortunately, this connection is mechanically and chemically less stable, may not be exposed to some aggressive cleaning solutions, and, in addition, may release traces of contaminants into the electrolyte solution.

In the case of a very...

Table of contents

• Cover
• Table of Contents
• Preface to the Second Edition
• Preface to the First Edition
• Foreword to the Second Edition
• Symbols and Acronyms
• 1 Introduction: An Overview of Practical Electrochemistry
• 2 Electrochemistry in Equilibrium
• 3 Electrochemistry with Flowing Current
• 4 Analytical Electrochemistry
• 5 Nontraditional Electrochemistry
• 6 Electrochemical Energy Conversion and Storage
• 7 Electrochemical Production
• AppendixAppendix
• Index
• End User License Agreement