Sustainable and Green Electrochemical Science and Technology (eBook)

Keith Scott (Autor)

eBook Download: EPUB

2017
John Wiley & Sons (Verlag)
9781118698105 (ISBN)

Infos

Sustainable and Green Electrochemical Science and Technology brings together the basic concepts of electrochemical science and engineering and shows how these are applied in an industrial context, emphasising the major role that electrochemistry plays within society and industry in providing cleaner, greener and more sustainable technologies. Electrochemistry has many applications for sustainability; it can be used to store energy, synthesise materials and chemicals, to generate power and to recycle valuable resources.

 

Coverage includes

• Electrochemistry, Electrocatalysis and Thermodynamics
• Electrochemical Cells, Materials and Reactors
• Carbon Dioxide Reduction and Electro-Organic Synthesis
• Hydrogen production and Water Electrolysis
• Inorganic Synthesis
• Electrochemical Energy Storage and Power Sources
• Electrochemical processes for recycling and resource recovery
• Fuel Cell Technologies

 

This book is targeted at both industrial and academic readers, providing a good technological reference base for electrochemistry. It will enable the reader to build on basic principles of electrochemistry, and takes these through to cell design for various and diverse applications.

KEITH SCOTT
School of Chemical Engineering and Advanced Materials, Newcastle University, UK

Inhalt

Preface xiii

Acknowledgement xv

1 Introduction to Electrochemical Sustainable Processes 1

1.1 Introduction 1

1.2 Effluent Treatment and Recycling 3

1.3 Green Electrochemistry 3

1.4 Electrochemistry and Energy Sustainability 4

1.5 Hydrogen Economy and Fuel Cells 7

1.6 Conclusions 24

References 25

2 Electrochemistry, Electrocatalysis and Thermodynamics 27

2.1 The Electrochemical Cell 27

2.2 Electrochemical Thermodynamics 29

2.3 Types of Electrochemical Reactions 38

2.4 Mass Transport and Electrochemical Reactions 49

2.5 Photoelectrochemistry 73

2.6 Electrochemical Impedance Spectroscopy 80

References 84

3 Electrochemical Cells, Materials and Reactors 87

3.1 Electrochemical Reactors 87

3.2 Fuel Cells 97

3.3 Batteries 101

3.4 Capacitors 103

3.5 Electrochemical Cell Engineering 106

References 124

4 Carbon Dioxide Reduction and Electro-Organic Synthesis 125

4.1 Electrochemical Reduction of Carbon Dioxide 125

4.2 Organic Synthesis 143

4.3 Green Electro-Organic Synthesis 151

4.4 Conclusions 156

References 157

5 Hydrogen Production andWater Electrolysis 159

5.1 Fossil Fuel Based Hydrogen Production 160

5.2 Hydrogen via Electrolysis 161

5.3 Photoelectrolysis 184

5.4 Thermal and Electrochemical Generation of Hydrogen fromWater 191

5.5 Chemical Production of Hydrogen 200

5.6 Conclusions 200

References 201

6 Inorganic Synthesis 203

6.1 Chemicals from the Electrolysis of Halides 203

6.2 Electrolytic Processes for Metal Processing 216

6.3 Inorganic Compounds and Salts 220

6.4 Generation of Chemical Oxidants 223

6.5 Conclusions 231

References 231

7 Electrochemical Energy Storage and Power Sources 233

7.1 Batteries 233

7.2 Supercapacitors 266

7.3 Biological Fuel Cells 271

References 287

8 Electrochemical Energy Systems and Power Sources: Fuel Cells 291

8.1 Introduction 291

8.2 Principle of Fuel Cell Operation 294

8.3 Fuel Cell Systems 296

8.4 Polymer Electrolyte Membrane Fuel Cells 300

8.5 Alkaline Fuel Cells 320

8.6 Medium and High Temperature Fuel Cells 326

8.7 Direct Alcohol Fuel Cells 344

8.8 Unitized Fuel Cells 356

References 359

9 Electrochemical Processes for Recycling and Resource Recovery 363

9.1 Electrochemical Membrane Separations 363

9.2 Electrochemical Oxidations 380

9.3 Recovery and Recycling of Dissolved Metals 381

References 383

Index 385

Textauszug

Chapter 1
Introduction to Electrochemical Sustainable Processes

1.1 Introduction

Electrochemistry is a fundamental process in life and plays an important role in a range of commercial technologies in industry. Electrochemistry is concerned with the transfer of charge, by the movement of ions, in a liquid or solid (or gaseous) phase through which electrochemical transformation of species can be achieved. Electrochemistry can be used to synthesize materials and chemicals, to generate power and to analyse and detect compounds and components. The applications of electrochemistry are quite diverse and span over a wide range of industries, including:

• Energy storage and power generation
• Synthesis of chemicals and materials
• Extraction and production of metals
• Recycling, water purification and effluent treatment
• Corrosion protection
• Analysis, sensors and monitors
• Metal and materials finishing and processing
• Semiconductor technology

Corrosion is an important industrial issue as great efforts and cost are required to minimize its effects. The majority of corrosion processes involve some form of electrochemical reaction of a metal component, which leads to a gradual loss of function or property of a device or component. Although the subject of corrosion is outside the scope of this book, its influence is important in the context of the selection of electrode materials. Electrode material selection must recognize that corrosion may occur during operation both in ‘current-on’ conditions and in standby, or open circuit, conditions. Current-on conditions can induce cathodic reduction of coatings and anodic dissolution of so called ‘inert anodes’. At standby conditions the electrodes are at different potentials to the current-on situation. This may result in a loss of protection of the material in the cell environment or an increased possibility of corrosion, for example in the case of fuel cell cathodes where potentials are higher at open circuit conditions. Such effects can be aggravated by the presence of corrosive chemical products and reagents, dissolved oxygen or other impurities. Electrochemical processes, by their very nature, involve the flow of current which can induce leakage or parasitic currents and thus cause and accelerate corrosion of components of the electrolytic systems.

Electrochemistry plays a vital part in sensors, analytical detection and in monitoring. Important applications include in polarography and anodic stripping voltammetry for trace metal ion analysis, ion selective electrodes, electrochemical biosensors and detectors.

Electrochemistry is used in the metal and material processing and semiconductor industries, producing components which are otherwise difficult to produce by mechanical means. The methods include machining, grinding, deburring and etching. Electrochemistry is used in the finishing of many components through the deposition of coatings (metallic, polymer) and through anodizing to produce surface oxide films. Electrophoretic painting is used widely in the motor industry for bodywork protection. Other applications are in electropolishing and in electrochemical cleaning, pickling and stripping.

Energy storage and generation through the application of electrochemical processes are provided by batteries, capacitors and fuel cells. The generation of electrical energy is caused by two ‘redox’ reactions (with a negative free energy) which occur spontaneously within a battery or fuel cell or from the liberation of an accumulated charge in a capacitor. There is a wide range of batteries for low, medium and high power applications and three of the most common are the lead/acid, nickel/metal hydride and lithium ion.

Fuel cells are devices for generating electrical power by the continuous supply of a fuel to one electrode and an oxidant to the other electrode. There are a variety of these devices which operate at low or high temperatures. The electrodes in fuel cells are different to those in batteries as they must generally be permeable to gases. In low temperature cells, catalytic gas diffusion electrodes are therefore used which are typically a composite structure of electrocatalyst, carbon, hydrophobic binder and a coating. Applications of fuel cells are in large scale power (combined electricity and heat) generation, vehicle traction and small scale remote site energy generation.

Electrochemical synthesis is used for production of both organic and inorganic chemicals. The two largest industries (in terms of tonnage) are for combined chlorine and caustic soda (NaOH) production (chlor-alkali) and aluminium electrowinning. These two processes use radically different cell technology, aluminium production being based on molten salt electrolysis at temperatures around 1000 °C, whilst the chlor-alkali industry is based on the electrolysis of aqueous brine solutions at relatively low temperatures. Other inorganic electrochemical processes include the production of hydrogen by water electrolysis, molten salt electrowinning of sodium, lithium and magnesium and electrowinning from aqueous electrolyte of copper, zinc and nickel. The purification of several metals is carried out by ‘electrorefining’ in which the impure metal is dissolved anodically in an electrolyte bath and the pure metal simultaneously electroplated onto a cathode. Furthermore, many species such as hydrogen peroxide and ozone, can be safely produced on-site electrochemically without the need for bulk storage of the hazardous reagent. The electrosynthesis of organic chemicals is mainly located in the fine chemical industries where the advantages of this technique have seen somewhere in the region of a hundred or so industrial processes developed. In bulk organic chemical manufacturing, electrochemical technology is used in relatively few syntheses as there is often a relatively large equipment cost associated with its use and a strong presence of heterogeneous catalysis. An important exception to this is the production of adiponitrile from acrylonitrile (an intermediate in the production of nylon) which competes well on the open market with a gas phase catalytic route.

An important part of electrochemical technology is that associated with the use of ion-exchange membranes. Membranes are both a vital component of many electrolytic cells and also a means of carrying out specific separations of ionic and non-ionic species and the formation of chemical products.

Areas where electrochemistry can play a major role are in sustainability of energy and chemical supplies. A significant area for the application of electrochemical technology is water purification and the recycling of materials and remediation of effluents (Comninellis and Chen, 2010).

1.2 Effluent Treatment and Recycling

The process industries are under environmental and economic pressure to make more effective use of the material resources used in the manufacture of commercial products. This impacts in several areas of process and product planning; the selection of the most appropriate starting materials and end product and the overall design of the process steps. Due to the inherent inefficiencies of physical and chemical processes there will be species and streams generated which are not a desirable part of the envisaged manufacturing process. If these materials are seen to have some immediate economic value, methods will be implemented to recover and re-use them. If the economics of re-use are not directly apparent then procedures are generally adopted to dispose of the material at short term minimum cost. In many cases these materials are potential pollutant and/or hazardous materials and their disposal should be looked at in a much larger context. The safe management of these materials, especially the more toxic and hazardous, is a major problem and is fraught with many issues; economic, social, political and technological. Nevertheless there are methods and procedures currently available, and in use, which can improve approaches to waste management based on strategies of re-use and recycling. The simple recovery of material and disposal without its re-use is less satisfactory; suitable ways, or alternative use, should ideally be found, for example the incineration of organic materials to produce process heat.

Electrochemical methods can be applied to the treatment of and recycling of many species present in solid, liquid or gaseous phases and compete commercially with many other methods not based on electrochemistry (Bersier et al. 1994). For example, conventional biological processes have been used in industrial waste treatment for many years and utilise either aerobic or anaerobic bacteria. New technologies are now being investigated which use the electron transfer ability of certain micro-organisms to generate electrical power in microbial fuel cells or to synthesize chemicals.

There are several established processes such as those for metal recovery by electrodeposition, ion separation by electrodialysis, water treatment using hypochlorite and the treatment of liquors bearing chromium species (Scott, 1995).

1.3 Green Electrochemistry

Electrochemistry can be seen as a branch of green chemistry which is ‘“concerned with the utilization of a set of principles that can reduce or eliminate the use of hazardous substances in the design, manufacture and application of chemical products’ (Bernando et al., 2010). Thus electrochemistry covers processes which relate to a reduction in the environmental impact of chemicals (and fuels) using improved production methods and...

Produkt-Details

• Erscheint lt. Verlag: 16.5.2017
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Chemie ► Physikalische Chemie
• Themenwelt: Technik ► Elektrotechnik / Energietechnik
• Schlagworte: batteries • Chemie • Chemistry • Electrochemical Engineering • Electrochemical Synthesis • Electrochemistry • Elektrochemie • Energie • Energy • Energy Storage • environmental protection • Fuel cells • Hydrogen, Batteries & Fuel Cells • Hydrogen Production • Industrial electrochemical technology • Nachhaltige u. Grüne Chemie • Nachhaltige u. Grüne Chemie • sustainability • Sustainable Chemistry & Green Chemistry • Wasserstoff, Batterien u. Brennstoffzellen
• ISBN-13: 9781118698105 / 9781118698105