Basic Electrochemistry for Biotechnology

Falk Harnisch, PhD, is a group leader at the Heimholtz Centre for Environmental Research and a Professor at Leipzig University, Leipzig, Germany. He has published extensively on microbiology and electrochemistry, and his awards and honors include the Helmholtz Young Investigators Group award as well as serving as President of the International Society of Microbial Electrochemistry and Technology (ISMET) 2021-2023. Tom Sleutels, PhD, is a researcher at the University of Groningen and Wetsus, European Centre of Excellence for Sustainable Water Technology in the Netherlands. His research focuses on microorganisms and their role in renewable energy and resource recovery processes. Annemiek ter Heijne, PhD, is Chair and Professor of Environmental Technology at Wageningen University & Research, The Netherlands. She is an environmental engineer studying different aspects and applications of microbial electrochemical technologies, and served as President of ISMET 2019-2021.

• List of Figures ixList of Boxes xxiPreface xxiii1 A Reader’s Guide to Basic Electrochemistry for Biotechnology 12 A Basic Introduction to Microbial Electrochemical Technologies 32.1 Introduction to Microbial Energy Conversion and Microbial Electrochemical Technologies 32.1.1 Microbial Conversions 32.1.2 Microbial Fuel Cells and Microbial Electrolysis Cells 52.2 Electroactive Microorganisms and Mechanisms of Extracellular Electron Transfer 72.2.1 Extracellular Electron Transfer Mechanisms: The Role Models of Electroactive Microorganisms 72.2.2 A Snapshot on Electroactive Microorganisms 82.3 Energetics: The Redox Tower and a Water Analogy 92.4 Wastewater Characteristics 132.4.1 Physical Wastewater Characteristics 142.4.2 Chemical Wastewater Characteristics 142.4.3 Organic Constituents in Wastewater 152.4.4 Biological Wastewater Characteristics 162.5 Microbial Electrochemical Technologies: Systems and Design 172.5.1 Main Components and Design 172.5.2 Operational Modes 182.5.3 Electrodes and Current Collectors 192.5.4 Ionic Charge Transport and Membranes 212.5.5 Lab Measurements and Criteria for Normalization 222.6 Short Alert on Terminology 23Questions 24References 253 Electrochemical Potential, Electrode Potential, and the Need for Reference Electrodes 273.1 Introduction to Electrochemical Potentials 273.1.1 A Physical-Chemical Approach Toward Electrochemical Potentials 283.2 Electrodes and Electrode Reactions 363.2.1 Definition of Electrodes and Electrochemical Half-Cells 363.2.2 Scientific Notation of Electrochemical Cells 373.2.3 Types of Electrodes 383.3 The Relative Electrode Potential and the Need for Reference Electrodes 403.3.1 Point of Reference for Electrode Potentials 423.3.2 Reference Electrodes Explained via the Water Analogy 45Questions 46References 474 Reaction Equations and Thermodynamics of Electrochemical Reactions 494.1 Introduction to Oxidation and Reduction Reactions and Thermodynamic Limits 494.2 How to Write and Balance Reaction Equations of (Bio)electrochemical Reactions 504.2.1 Reaction Equations for the Hydrogen Fuel Cell 514.2.2 Reaction Equations for a Microbial Electrolysis Cell 534.3 Thermodynamics of Electrochemical Conversions 574.3.1 Calculations Assuming Standard Conditions 574.3.2 The Effect of Actual Concentrations on Gibbs Free Energy Change 624.3.3 The Effect of Temperature on Gibbs Free Energy Change 65Questions 68References 685 Static Electrochemical Methods 695.1 Introduction to Static Electrochemical Methods 695.2 What Is a Three-Electrode Arrangement, a Potentiostat or Power Supply, and for What Are They Needed? 705.3 The Electrochemical Double Layer and Capacitive Current 745.4 Potentiometry, Amperometry, Coulometry, and Constant Current Measurements 785.5 Chronoamperometry 82Questions 87References 886 Electrochemical Kinetics 896.1 Introduction to Electrochemical Kinetics 896.2 Basics of Electrochemical Kinetics 906.3 Electrochemical Reversibility 916.4 Overpotentials 946.5 The Overpotential Due to Mass Transfer 986.6 Potential-Current Plots and Electrode Kinetics 1016.7 The Butler–Volmer Equation 1036.8 Tafel Equation and Tafel Plots 1066.9 Electrocatalysis 108Questions 113References 1147 Dynamic Electrochemical Methods 1157.1 Introduction to Electrochemical Methods with Changing Electrode Potential 1157.2 Voltammetry 1177.3 Performing Dynamic Electrochemical Methods Using Potentiostats: Discriminating Capacitive and Faradaic Current 1177.3.1 The Principles of Linear Sweep Voltammetry 1207.4 Cyclic Voltammetry 1237.4.1 General Considerations and Basic Data Analysis 1237.4.2 Studying Biofilm Electrodes Using Cyclic Voltammetry 1317.4.3 Experimental Design and Limits of Information from Data 1347.5 Redox-Active Components in Microorganisms 1367.6 Acquisition of Polarization and Power Curves Using Stepwise Chronoamperometry and Chronopotentiometry 1397.7 Acquisition of Polarization Curves Using External Resistance 1457.8 Electrochemical Impedance Spectroscopy 147Questions 152References 1528 Electrochemical Analysis of Reactors 1558.1 Introduction to Characterization of Microbial Electrochemical Cells 1558.2 Mass and Electron Balances and Efficiency of Conversions 1578.2.1 Establishing Balances for Mass and Electrons 1578.2.2 Removal Efficiency 1588.2.3 Coulombic Efficiency 1598.3 Polarization and Power Curves: Analysis of Measured Data 1618.4 Internal Resistance and Potential Losses 1688.5 Energy Efficiency and Voltage Efficiency 1748.6 Ionic Current and Transport Numbers 1768.6.1 Ionic Current for the Specific Removal and Recovery of Ions 1768.6.2 Ionic Current and pH Gradients 177Questions 178References 1799 Seizing the Beauty and Acknowledging the Complexity of Basic Electrochemistry for Biotechnology 181Appendix A Abbreviations 185Appendix B Symbols with Definition and Unit 187Appendix C Solutions to Exercises 193Appendix D Tabulated Values 217Index 219