Microbial Electrochemical Technologies E-Book
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- Herausgeber: Wiley-VCH GmbH
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
A one-stop guide to the future of sustainable energy production
The search for sustainable energy sources powered by renewable, non-fossil fuel resources is one of the great scientific challenges of the era. Microorganisms such as bacteria and algae have been shown to function as the basis of a microbial fuel cell, which can operate independently of an electrical power grid on the basis of renewable feed sources. These fuel cells have shown applications ranging from powering implantable biomedical devices to purifying rural water sources, and many more.
Microbial Electrochemical Technologies offers a one-stop shop for researchers and developers of technologies incorporating these microbial fuel cells. Beginning with the fundamental processes involved in microbial energy production and the key components of a bioelectrochemical system (BES), it then surveys the major BES types and crucial aspects of technological development and commercialization. The result is an indispensable introduction to these vital power sources and their myriad applications.
Microbial Electrochemical Technologies readers will also find:
- Detailed treatment of BES types including fuel cells, electrolysis and electrosynthesis cells, and more
- Discussion of commercialization aspects including modelling, performance analysis, and life cycle assessment
- An authorial team with decades of combined experience on three continents
Microbial Electrochemical Technologies is a useful reference for electrochemists, microbiologists, biotechnologists, and bioengineers.
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Seitenzahl: 1482
Veröffentlichungsjahr: 2023
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Table of Contents
Cover
Table of Contents
Title Page
Copyright
Preface
Volume 1
1 Fuel Cells and Biofuel Cells
1.1 Energy Demand and Current Energy Scenario
1.2 Fundamentals of Fuel Cells
1.3 Introduction to Fuel Cells and Biofuel Cells
1.4 Basic Description of Bioelectrochemical Systems
1.5 An Overview of Bioelectrochemical Systems
1.6 Organization of the Book
References
2 Electrochemistry Analytical Techniques and Interpretation of the Results
2.1 Electrochemistry Fundamentals
2.2 Introduction to Electrochemistry (Basics of Electrochemistry)
2.3 Basics of Voltammetry: Cyclic and Linear Sweep Voltammetry
2.4 Electrochemical Impedance Spectroscopy: Nyquist and Bode Plots
2.5 Rotating Disc Electrode Experiments: Koutecky–Levich Equations
2.6 Tafel Plot, Butler–Volmer Kinetics
2.7 Losses in Bioelectrochemical Systems
2.8 Application of BESs
2.9 Power Generation: Power Density and Polarization Plots
2.10 Analysis and Interpretation of These Test Results with Examples
2.11 Tafel Test
2.12 Cyclic Voltammetry Test
2.13 Linear Sweep Voltammetry
2.14 Summary
References
3 Bioelectrochemical Systems: Configurations and Materials
3.1 Introduction
3.2 Reactor Configurations for Bioelectrochemical Systems
3.3 Electrode Materials Used for Bioelectrochemical Systems
3.4 Membranes Used for Bioelectrochemical Systems
3.5 Materials of Construction Used for Pilot‐Scale Investigations
3.6 Power Management System for Bioelectrochemical Systems
3.7 Future Perspectives in Terms of Scalability and Summary
References
4 Biotic Components of Different Types of Bioelectrochemical Systems
4.1 Introduction
4.2 Exoelectrogens and Electrotrophs Cultivated in Different Types of BESs
4.3 Concept of Extracellular Electron Transfer Between Electrode and Exoelectrogens
4.4 Photosynthetic Microbial Electron Transfer
4.5 Effect of Operating Parameters on Biofilm Formation and Thickness
4.6 Quorum Sensing and Quorum Quenching Effects
4.7 Bottlenecks and Future Prospective
4.8 Summary
References
5 Role of Catalysts in Bioelectrochemical Systems
5.1 Introduction
5.2 Fundamental of BES
5.3 Microbial Interaction with Electrodes
5.4 Advanced Nanostructure Modification of Anodes
5.5 Oxygen Reduction Reaction at the Cathode: Fundamentals
5.6 Conclusion and Future Perspective
References
6 Infrared and Visible Spectroscopy: Fourier Transform Infrared Spectroscopy and Ultraviolet–Visible Spectroscopy
6.1 Infrared Spectroscopy
6.2 UV–Vis Spectroscopy
References
7 Inductively Coupled Plasma Optical Spectroscopy and Atomic Absorption Spectroscopy
7.1 Introduction
7.2 Inductively Coupled Plasma Mass Spectrometry (ICP‐MS)
7.3 Inductively Coupled Plasma Optical Emission Spectrometry
7.4 Atomic Absorption Spectroscopy
References
8 Nitrogen Sorption Measurements and Thermal Analysis Techniques
8.1 Nitrogen Sorption Measurements
8.2 Thermal Analysis Techniques
8.3 Conclusion
Acknowledgement
References
9 Material Characterization for Synthesized Catalysts: Morphology, Microstructure, and Crystallographic Phase
9.1 Introduction
9.2 Morphology, Crystallography, and Microstructure
9.3 Electron Microscopes
9.4 Energy‐Dispersive X‐ray Microanalysis
9.5 X‐ray Diffraction
9.6 Conclusions
References
10 X‐Ray Photoelectron Spectroscopy and X‐Ray Fluorescence Spectroscopy
10.1 X‐Ray Photoelectron Spectroscopy
10.2 X‐Ray Fluorescence
10.3 Conclusions
References
11 Atomic Force Microscopy and Raman Spectroscopy
11.1 Atomic Force Microscopy
11.2 Raman Spectroscopy
11.3 Conclusions
References
12 Different Types of Bioelectrochemical Systems
12.1 Introduction and Types of Bioelectrochemical Systems
12.2 Advantages and Historical Development of Different Bioelectrochemical Systems
12.3 Future Variants and New‐Age Bioelectrochemical Systems
12.4 Summary
References
13 Microbial Fuel Cell
13.1 Introduction
13.2 Microbial Fuel Cells: Components and Mechanism
13.3 Different Substrates for Microbial Fuel Cells
13.4 Role of Electrode Materials in Microbial Fuel Cells
13.5 Different Types of Separator/Membrane Used in Microbial Fuel Cells
13.6 Role of Microbial Consortium as Electrocatalyst
13.7 Performance Evaluation of Microbial Fuel Cells
13.8 Pilot and Field‐Scale Application of Microbial Fuel Cells
13.9 Recent Advancements and Future Prospective
13.10 Summary
References
14 Microbial Electrolysis Cell
14.1 Introduction
14.2 Different Valuables Recovered Through Microbial Electrolysis Cells
14.3 Role of Cathode Catalysts in Microbial Electrolysis Cells
14.4 Different Types of Biocatalysts Used in MEC
14.5 Role of Imposed Potential in MEC
14.6 Recent Advancements and Future Prospective
14.7 Conclusion
References
15 Microbial Electrosynthesis: A Biobased Pathway for the Production of Value‐Added Chemicals Through Carbon Sequestration
15.1 Introduction
15.2 Organic Compounds Synthesized Through MES
15.3 Imperative Role of Operating Parameters on MES
15.4 Biocatalysts Used in MES
15.5 Product Separation Techniques Employed in MES
15.6 Recent Advancements
15.7 Performance Evaluation of MES Systems
15.8 Bottlenecks and Way Forward
15.9 Summary
References
Volume 2
16 Microbial Desalination Cell
16.1 Introduction
16.2 Working Principle of an MDC
16.3 Configurations of MDCs
16.4 Catalysts Implemented in MDCs
16.5 Wastewater Treatment Using MDCs
16.6 Microbial Electrodialysis Cells
16.7 Resource Recovery Using MDCs
16.8 Limitations and Present Bottlenecks of MDC
16.9 Way Forward
References
17 Progressive Transformation of Microbial Fuel Cells (MFCs) to Sediment MFCs, Plant MFCs, and Constructed Wetland Integrated MFCs
17.1 Introduction
17.2 Configuration of P‐MFCs, S‐MFCs, and CW‐MFCs with a Basic Difference
17.3 Electrodes Used in CW‐MFCs, P‐MFCs, and S‐MFCs
17.4 Power Output Performance and Its Limiting Factors for S‐MFCs, P‐MFCs, and CW‐MFCs
17.5 Bioremediation Potential of CW‐MFCs, P‐MFCs, and S‐MFCs
17.6 Real‐world and Possible Potential Applications of CW‐MFCs, P‐MFCs, and S‐MFCs
17.7 Hybrid Technologies Using S‐MFCs, P‐MFCs, and CW‐MFCs
17.8 Limitations and Way Forward for S‐MFCs, CW‐MFCs, and P‐MFCs
17.9 Conclusion and Future Perspective for S‐MFCs, P‐MFCs, and CW‐MFCs
Acknowledgements
References
18 Microbial Remediation Cell
18.1 Introduction
18.2 Degradation Mechanism in the Anodic Chamber of Microbial Remediation Cell
18.3 Degradation Mechanism in the Cathodic Chamber of Microbial Remediation Cell
18.4 Basic Principle of Microbial Remediation Cell
18.5 Application of Microbial Remediation Cell for Pollutant Removal
18.6 Conclusion and Way Forward
References
19 Enzymatic Fuel Cells and Biosensors
19.1 Introduction to Enzymatic Fuel Cells
19.2 Enzymatic Fuel Cell Components
19.3 Applications of EFCs
19.4 Introduction to Biosensors
19.5 MFC‐Based Biosensors
19.6 Real‐Life Applications of MFC‐Based Biosensors
19.7 Summary
References
20 Photosynthetic Microbial Fuel Cell, Biophotovoltaic Cell, and Microbial Carbon‐Capture Cell
20.1 Introduction
20.2 Working Principle
20.3 Different Photosynthetic Microbes Used in BESs
20.4 Valuables Recovered from Photosynthetic Microbes
20.5 Parameters Affecting the Performance of PMFCs, Biophotovoltaic Cell, and MCCs
20.6 Applications of the Photosynthetic Microbial Fuel Cell
20.7 Bottlenecks and Recent Developments
20.8 Summary
References
21 Modelling of Bioelectrochemical Systems: Biophysicochemical Processes and Mathematical Methods
21.1 Introduction
21.2 Fundamental Processes/Phenomena of BESs and the Need for Mathematical Modelling
21.3 Classification BES Models
21.4 Computational Methodologies
21.5 Bio‐physical‐(electro)chemical Processes/Phenomena and Mathematical Formulation
21.6 Reality and Future Perspective of Mathematical Modelling in BES Research
21.7 Conclusion
References
22 Pilot‐Scale Case Performance of Bioelectrochemical Systems
22.1 Introduction
22.2 Long‐term Performance of the Pilot MFCs
22.3 Piloting Efforts of BES
22.4 Challenges and Technological Factors Behind the Scaling Up of BES
22.5 Cost Analysis of BES
22.6 Conclusion
References
23 Statistical Methods for Modelling and Performance Analysis of Bioelectrochemical Systems
23.1 Introduction
23.2 Tools for Statistical Analysis
23.3 Role of Statistics in BES Research
23.4 Statistical Methods for BES Modelling
23.5 Introduction to ANOVA and RSM
23.6 Application of Optimization Experiments in BES
23.7 Statistical Modelling and Future Perspective
23.8 Conclusion
References
24 Performance Comparison and Integration of Bioelectrochemical Systems with Other Wastewater Treatment Technologies
24.1 Introduction
24.2 MFC vs. Anaerobic Digestion for Treatment of High‐Strength Wastewater
24.3 Bio‐electro‐Fenton vs. Electrochemical Oxidation for Pollutant Removal
24.4 Dark Fermentation vs. MEC for Hydrogen Production
24.5 Microbial Carbon‐Capture Cell vs. Photobioreactor for Nutrient Recovery
24.6 Comparison of Sediment MFC with Other In Situ Soil Remediation Techniques
24.7 Comparison of Constructed Wetland‐MFC with Conventional Constructed Wetland
24.8 Future Perspectives
24.9 Conclusion
References
25 Circular Bioeconomy Implementation and Life‐Cycle Assessment of Bioelectrochemical Systems
25.1 Introduction to Circular Bioeconomy Concepts
25.2 Exploring Circular Bioeconomy in BES
25.3 Adopting Circular Bioeconomy Further in BES Research
25.4 Evaluation Techno‐economic Sustainability in BES
25.5 Life‐Cycle Assessment of BES
25.6 Satisfying SDGs, Different Aspects in Respect to BES
25.7 Summary
References
26 Way Forward and Conclusion
26.1 Way Forward with Respect to Third‐ and Fourth‐Generation Bioelectrochemical Systems
26.2 Application of Bioelectrochemical Systems for Resource Recovery
26.3 Future Research Direction for Biotic Components
26.4 Future Research Direction for Search of Cathode and Anode Catalysts
26.5 Future Research Direction for Membrane Electrode Assemblies
26.6 Applicability of BES in Future Wastewater Treatment Plants
26.7 Conclusion
References
Appendix A
Appendix B
Index
End User License Agreement
List of Tables
Chapter 3
Table 3.1 Characteristics of some of the ceramic‐based proton exchange memb...
Chapter 4
Table 4.1 Most notable microbiota cultured in different bioelectrochemical ...
Table 4.2 The application of QS and QQ mechanisms in different types of BES...
Chapter 5
Table 5.1 Performance of MFCs with the conventional and nanocomposite‐based...
Table 5.2 Various air‐cathode materials and their power density performance...
Chapter 6
Table 6.1 Functional group and its quantified frequencies.
Table 6.2 Functional group and its quantified frequencies.
Table 6.3 Functional group and its quantified frequencies.
Table 6.4 Functional group and its quantified frequencies.
Table 6.5 Functional group and its quantified frequencies.
Table 6.6 Correlation between the wavelength and the chromophore groups.
Table 6.7 Wavelengths for the most used solvents.
Chapter 7
Table 7.1 Advantages and disadvantages of selected methods for analysis of ...
Table 7.2 ICP‐MS application areas.
Table 7.3 Conversion table for units.
Table 7.4 Flame properties.
Table 7.5 Example to establish the temperature programme for Pb(II) analysi...
Chapter 8
Table 8.1 Thermal analysis methods.
Table 8.2 Reaction type of TG curves.
Table 8.3 Reaction type with heat change.
Chapter 9
Table 9.1 Substantial distinctions between BSE and SE (Jeol Company 2022; N...
Table 9.2 Differences between SEM and TEM.
Table 9.3 The relation between
d
‐spacings and lattice parameters.
Table 9.4 XRD peak list of MgO catalyst obtained through the instrument sof...
Chapter 11
Table 11.1 Roughness parameters for graphite‐based material immersed in vit...
Table 11.2 Characteristic frequencies of some functional groups.
Table 11.3 Character table of the
C
2
v
point group and the meaning of parame...
Table 11.4 Mulliken symbols and their meaning.
Table 11.5 Γ modes calculation according to the existing vectors in the mol...
Table 11.6
C
2
calculation according to the existing vectors in the molecule...
Table 11.7
σ
v
(
xz
) calculation according to the existing vectors in th...
Table 11.8
σ
v
′(
yz
) calculation according to the existing vectors in th...
Table 11.9 Character table of the
C
2
v
point group.
Chapter 13
Table 13.1 Different substrates used in MFCs for power generation.
Table 13.2 Various membrane/separators reported in the literature for appli...
Chapter 14
Table 14.1 Different biofuels and biochemicals recovered through microbial ...
Table 14.2 Different cathode catalysts used in microbial electrolysis cells...
Table 14.3 Different biocatalysts employed in microbial electrolysis cells....
Table 14.4 Standard electrode potential of different electron donor and acc...
Chapter 15
Table 15.1 Different products recovered via MES with their respective react...
Chapter 17
Table 17.1 Power output performance of CW‐MFC, S‐MFC, and P‐MFC.
Chapter 18
Table 18.1 Bioremediation of pollutants in the anodic chamber of microbial ...
Table 18.2 Bioremediation of pollutants in the cathodic chamber of a microb...
Chapter 20
Table 20.1 Photosynthetic oxygenic and anoxygenic bacteria cultured in BESs...
Table 20.2 Photosynthetic microalgal species utilized in BESs.
Table 20.3 Potential application/value‐added derivatives from phototrophs....
Table 20.4 Wastewater treatment through different PMFCs with the recovery o...
Chapter 22
Table 22.1 Experiments of scaling up of MFCs with less than 100 l anodic ch...
Table 22.2 Cost of fabrication of different scaled‐up MFCs
Chapter 23
Table 23.1 Summary of statistical approaches used in optimization of BESs....
Table 23.2 Relevant terms used in statistical modelling.
Table 23.3 Summary table for choosing an experimental design.
Chapter 24
Table 24.1 Performance comparison between MFC, AD, and integrated AD and MF...
Table 24.2 The performance comparison of EO and BEF processes for the remov...
Table 24.3 Performance comparison between DF, MEC, and DF‐MEC processes for...
Table 24.4 The pollutant removal efficiency of CW and CW‐MFC for different ...
Chapter 25
Table 25.1 Energy and resource recovery in microbial fuel cell.
Table 25.2 Energy and resource recovery in microbial electrolysis cell.
Table 25.3 Novel approaches in MES.
List of Illustrations
Chapter 1
Figure 1.1 Anode and cathode potential in (bio)electrochemical system.
HRES
...
Figure 1.2 Classification of chemical and biological fuel cells.
Figure 1.3 General configuration and emerging applications of bioelectrochem...
Chapter 2
Figure 2.1 Basic electrochemical arrangement for synthesis; reaction solutio...
Figure 2.2 (a) Electron flow in an electrochemical reaction; (b) the Helmhol...
Figure 2.3 Assembly of the three‐electrode system: WE, RE, and CE.
Figure 2.4 (a) Typical CV scan for a redox reaction and (b) mechanism showin...
Figure 2.5 A typical polarization curve that shows how things are not perfec...
Figure 2.6 (a) Voltage and current response for two electrodes used in fuel ...
Figure 2.7 LSV curves for small substrates corrosion testing over a wider po...
Figure 2.8 A polished sample (curve 1), a sample anodized in SA and coated w...
Figure 2.9 Tafel curves for a system using coated and uncoated SUS304 cathod...
Figure 2.10 Comparison of coated and uncoated SUS304 cathodes in the EF syst...
Figure 2.11 Linear sweep voltammograms of coated and uncoated SUS304 cathode...
Chapter 3
Figure 3.1 Schematic of aqueous cathode configuration of bioelectrochemical ...
Figure 3.2 Schematic of air cathode configuration of a bioelectrochemical sy...
Figure 3.3 Connections for air‐cathode microbial fuel cells connected in (a)...
Figure 3.4 Bioelectrochemical system configuration for (a) hydrogen producti...
Figure 3.5 Configuration of a microbial desalination cell.
Figure 3.6 Configuration of a microbial carbon‐capture cell.
Figure 3.7 Commonly used electrode materials in bioelectrochemical systems: ...
Figure 3.8 Separators commonly used in bioelectrochemical systems: (a) Nafio...
Figure 3.9 Power management system for harvesting the power from a microbial...
Chapter 4
Figure 4.1 A typical microbial fuel cell cultivated with different exoelectr...
Figure 4.2 Different electron transfer mechanisms in exoelectrogens.
Figure 4.3 Stepwise biofilm formation of exoelectrogens on the surface of th...
Figure 4.4 Quorum sensing mediated electron transfer in
P
.
aeruginosa
strain...
Chapter 5
Figure 5.1 Schematic presentation of essential properties, classification, a...
Figure 5.2 Schematic illustration of synthesis of natural waste‐derived elec...
Figure 5.3 Schematic representation demonstrating the various types of ORR c...
Chapter 6
Figure 6.1 Electromagnetic spectrum.
Figure 6.2 IR domain.
Figure 6.3 Formaldehyde IR absorption maximum.
Figure 6.4 Stretching and deformation vibrations of formaldehyde.
Figure 6.5 Methods for FTIR analysis of solid samples.
Figure 6.6 The influence of the concentration on the obtained FTIR spectrum ...
Figure 6.7 ATR types: with one reflection and with many reflections.
Figure 6.8 Comparison between spectra obtained by pelletization with KBr and...
Figure 6.9 Absorbance of existing chemical bonds in organic compounds.
Figure 6.10 Single‐beam spectrophotometer scheme.
Figure 6.11 Dual‐beam spectrophotometer scheme.
Figure 6.12 Light intensity when passing through the sample cuvette.
Figure 6.13 Representation of an absorption spectrum.
Figure 6.14 Absorption spectrum characteristics.
Figure 6.15 Correlation between absorption spectrum and calibration curve (
A
...
Figure 6.16 Molecular orbital diagram: possible transitions.
Figure 6.17 Bacterial growth curve.
Chapter 7
Figure 7.1 Schematic diagram of inductively coupled plasma mass spectrometry...
Figure 7.2 ICP‐MS interface diagram showing plasma and interface sampling pr...
Figure 7.3 Quadrupole ICP‐MS.
Figure 7.4 Scheme of a typical TOF‐ICP‐MS.
Figure 7.5 Magnetic sector ICP‐MS.
Figure 7.6 ICP‐OES principle.
Figure 7.7 Sample introduction and the nebulizer chamber.
Figure 7.8 Types of nebulizers: (a) pneumatic concentric nebulizer; (b) pneu...
Figure 7.9 Inductive coupled plasma torch used in ICP systems. A – tangentia...
Figure 7.10 A single detector (sequential‐type monochromator) ICP‐AES system...
Figure 7.11 A Rowland circle ICP‐AES system.
Figure 7.12 Multiple monochromator ICP‐AES instrument.
Figure 7.13 Spectral interference of iron with cadmium.
Figure 7.14 Energy level diagram illustrating the excitation, ionization, an...
Figure 7.15 Atomic absorption spectroscopy (AAS).
Figure 7.16 Flame burner.
Figure 7.17 Flame structure.
Figure 7.18 Line source – Hollow cathode lamp.
Figure 7.19 Electrodeless discharge lamp (EDL).
Figure 7.20 Monochromator.
Figure 7.21 Scheme of the longitudinally heated graphite furnace atomizer.
Figure 7.22 Schematic diagram of the Varian VGA‐77 vapour generation accesso...
Chapter 8
Figure 8.1 Type I isotherm of adsorption–desorption (a) pores smaller than 1...
Figure 8.2 Type II isotherm of adsorption–desorption.
Figure 8.3 Type III isotherm of adsorption–desorption.
Figure 8.4 Type IV isotherm of adsorption–desorption, (a) hysteresis is pres...
Figure 8.5 Types of hysteresis.
Figure 8.6 Type V isotherm of adsorption–desorption.
Figure 8.7 Type VI adsorption–desorption isotherms.
Figure 8.8 Surface area and pore size analyser (Quantachrome Nova 1200e)....
Figure 8.9 Non‐elutriation plugs and cells with 9 mm bulb.
Figure 8.10 Dewar vessel.
Figure 8.11 Quantachrome NovaWin software (gas selection).
Figure 8.12 Quantachrome NovaWin software (data details).
Figure 8.13 Quantachrome NovaWin software (methods).
Figure 8.14 Quantachrome NovaWin software (points selection).
Figure 8.15 Quantachrome NovaWin software (surface area points selection).
Figure 8.16 Quantachrome NovaWin software (surface area summary).
Figure 8.17 Quantachrome NovaWin software (total pore volume summary).
Figure 8.18 Quantachrome NovaWin software (Alpha S method summary).
Figure 8.19 Quantachrome NovaWin software (pore size distribution).
Figure 8.20 Quantachrome NovaWin software (DFT model).
Figure 8.21 Simultaneous thermal analyser (TG/DSC).
Figure 8.22 A schematic diagram of a thermobalance.
Figure 8.23 Interpretation of TG curves.
Figure 8.24 A schematic diagram of derivative thermobalance.
Figure 8.25 A schematic diagram for DTA apparatus.
Figure 8.26 DTA curve with exothermic and endothermic peaks.
Figure 8.27 Thermal transitions measured by DSC.
Figure 8.28 The TG curve of CaC
2
O
4
·H
2
O decomposition.
Figure 8.29 The effect of the atmosphere on the decomposition of CaC
2
O
4
·H
2
O ...
Figure 8.30 TG, DTG, and DTA curves of H
3
PW
12
O
40
·6H
2
O at 2.5, 5, 7.5, and 10...
Figure 8.31 TG curves of constitutional water loss at 2.5, 5, 7.5, and 10 K/...
Chapter 9
Figure 9.1 Examples of Miller indices on a cubic lattice system.
Figure 9.2 SEM images of a MgO catalyst at different magnifications (a) 13,0...
Figure 9.3 Comparison of (a) TEM, (b) HR‐TEM, and (c) SEM images of a bimeta...
Figure 9.4 SEM‐EDS image and the elemental composition report.
Figure 9.5 Scheme of Bragg's law.
Figure 9.6 XRD of MgO catalyst.
Chapter 10
Figure 10.1 Photoelectrons emitted due to an incident photon.
Figure 10.2 The atom and the X‐ray.
Figure 10.3 The emission of the X‐ray fluorescence.
Figure 10.4 A multi‐element fluorescence graphic obtained from
109
Cd.
Figure 10.5 X‐ray fluorescence spectroscopy was used to perform a semi‐quant...
Chapter 11
Figure 11.1 Basic components of AFM.
Figure 11.2 3D AFM images of silica standard at different scanning scales: (...
Figure 11.3 3D AFM image of a Fisher standard at different scanning scales: ...
Figure 11.4 2D AFM image of a Fisher standard (a) and profile heights from t...
Figure 11.5 The change of attraction–repulsion forces during approach and re...
Figure 11.6 Force–distance correlation in contact, non‐contact, and intermit...
Figure 11.7 (a) 2D image of graphite‐based material immersed in vitamin C (1...
Figure 11.8 (a) 3D image of graphite‐based material immersed in vitamin C (1...
Figure 11.9 The influence of the Raman effect on the spectra. (a) Incident l...
Figure 11.10 Diagram of energy levels associated with Stokes and anti‐Stokes...
Figure 11.11 Raman spectra of SiO
2
.
Figure 11.12 Algin (alginic acid) sample obtained at different laser intensi...
Figure 11.13 An example of a Raman spectra.
Figure 11.14 Representation of the vectors in the water molecule.
Figure 11.15 Representation of the identity (
E
) for each vector in the water...
Figure 11.16 Representation of
C
2
for each vector in the water molecule.
Figure 11.17 Representation of
σ
v
(
xz
) for each vector in the water mol...
Figure 11.18 Representation of
σ
v
′(
yz
) for each vector in the water mol...
Chapter 12
Figure 12.1 Dual‐chambered set‐up for BES.
Figure 12.2 Single‐chambered microbial electrolysis cell.
Figure 12.3 Historical development in BES research field.
Chapter 13
Figure 13.1 Factors affecting the performance of MFCs in terms of wastewater...
Figure 13.2 Schematic representation of a dual‐chambered MFC (SPEEK: sulphon...
Figure 13.3 Schematic representation of different electron transport mechani...
Figure 13.4 Polarization curve (a) and power density plot (b) of MFC.
Chapter 14
Figure 14.1 A schematic representation of a typical microbial electrolysis c...
Figure 14.2 A microbial electrolysis cell–anaerobic digestion coupled system...
Chapter 15
Figure 15.1 Schematic representation of a conventional MES set‐up and the re...
Chapter 16
Figure 16.1 A typical microbial desalination cell.
Figure 16.2 Schematic illustration of an osmotic microbial desalination cell...
Figure 16.3 Schematic illustration of a microbial electrodialysis and chemic...
Figure 16.4 Schematic representation of (a) submersible MDC and (b) microbia...
Figure 16.5 Stacked MDC.
Figure 16.6 Up‐flow MDC with air cathode.
Figure 16.7 Schematic illustration of different MDC configurations: (a) CEM ...
Figure 16.8 Operation challenges of MDCs.
Chapter 17
Figure 17.1 Origin and main functions of MFCs, S‐MFCs, P‐MFCs, and CW‐MFCs, ...
Figure 17.2 Schematic of (a) plant‐MFC, (b) constructed wetland‐MFC, and (c)...
Figure 17.3 Generic bioremediation mechanisms.
Chapter 18
Figure 18.1 A schematic of anodic and cathodic degradation of pollutants in ...
Figure 18.2 Degradation mechanism of congo red in the anodic chamber of a mi...
Figure 18.3 Mechanism of acid orange 7 degradation in the cathodic chamber o...
Figure 18.4 The basic principles involved during the remediation of heavy me...
Chapter 19
Figure 19.1 Representation of membrane‐less EFC.
Figure 19.2 Schematic of enzyme orientation (Sakai et al. 2018). (a) Curvatu...
Figure 19.3 Diagram of the DET pathway proposed for GOx physisorbed with mul...
Figure 19.4 Schematic showing cellulose hydrolysis and glucose oxidation usi...
Figure 19.5 Presentation of implantable EFCs.
Figure 19.6 MFC toxicity sensors: (A) paper MFC (Chouler et al. 2018) and (B...
Chapter 20
Figure 20.1 Schematic representation of the complete scenario for photoautot...
Figure 20.2 A schematic representation of photobioreactor‐assisted microbial...
Figure 20.3 A typical photosynthetic bacteria‐assisted biophotovoltaic cell....
Figure 20.4 Schematic representation of algae‐assisted microbial carbon‐capt...
Chapter 21
Figure 21.1 An overview of the fundamental processes involved in bioelectroc...
Figure 21.2 Key biological, physical, and (electro)chemical processes/phenom...
Figure 21.3 Classification of models based on principles/methods used for mo...
Figure 21.4 Typical boundary conditions used in modelling of biofilms.
Chapter 22
Figure 22.1 (a) Bioelectric toilet set‐up with 1500‐l volume MFC stack insta...
Chapter 23
Figure 23.1 Depiction of statistical tools for analysis of BES performance....
Figure 23.2 Depiction of statistical approaches for BES modelling. SLR: simp...
Chapter 24
Figure 24.1 Flowchart of BESs, their function, and products.
Figure 24.2 Schematic representation of a typical MFC and electricity produc...
Figure 24.3 Performance comparison of MFC vs. AD for high‐strength wastewate...
Figure 24.4 Schematic representation of a typical MEC for biohydrogen produc...
Figure 24.5 Microbial carbon‐capture cell.
Figure 24.6 Different technologies for remediation of soil and sediment cont...
Figure 24.7 Types of constructed wetlands for wastewater treatment.
Chapter 25
Figure 25.1 BES research contributing to SDGs.
Guide
Cover
Table of Contents
Title Page
Copyright
Preface
Begin Reading
Appendix A
Appendix B
Index
End User License Agreement
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Microbial Electrochemical Technologies
Fundamentals and Applications
Volume 1
Edited by Makarand M. Ghangrekar, Rao Y. Surampalli, Tian C. Zhang, and Narcis M. Duteanu
Microbial Electrochemical Technologies
Fundamentals and Applications
Volume 2
Edited by Makarand M. Ghangrekar, Rao Y. Surampalli, Tian C. Zhang, and Narcis M. Duteanu
Editors
Prof. Makarand M. GhangrekarIIT KharagpurKharagpur 721302West BengalIndia
Dr. Rao Y. SurampalliGlobal Institute for Energy, Environment and SustainabilityLenexaKS 66285USA
Dr. Tian C. ZhangUniversity of Nebraska‐LincolnDepartment of Civil and Environmental EngineeringLincolnNE 68182USA
Assoc. Prof. Narcis M. DuteanuTimisoara Polytechnic UniversityTimisoara 300223Romania
Cover Image: Courtesy of Makarand M. Ghangrekar
All books published by WILEY‐VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.
Library of Congress Card No.: applied for
British Library Cataloguing‐in‐Publication Data A catalogue record for this book is available from the British Library.
Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d-nb.de>.
© 2024 WILEY‐VCH GmbH, Boschstraße 12, 69469 Weinheim, Germany
All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.
Print ISBN: 978‐3‐527‐35372‐9ePDF ISBN: 978‐3‐527‐83898‐1ePub ISBN: 978‐3‐527‐83899‐8oBook ISBN: 978‐3‐527‐83900‐1
Editors
Prof. Makarand M. GhangrekarIIT KharagpurKharagpur 721302West BengalIndia
Dr. Rao Y. SurampalliGlobal Institute for Energy, Environment and SustainabilityLenexaKS 66285USA
Dr. Tian C. ZhangUniversity of Nebraska‐LincolnDepartment of Civil and Environmental EngineeringLincolnNE 68182USA
Assoc. Prof. Narcis M. DuteanuTimisoara Polytechnic UniversityTimisoara 300223Romania
Cover Image: Courtesy of Makarand M. Ghangrekar
All books published by WILEY‐VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.
Library of Congress Card No.: applied for
British Library Cataloguing‐in‐Publication Data A catalogue record for this book is available from the British Library.
Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d-nb.de>.
© 2024 WILEY‐VCH GmbH, Boschstraße 12, 69469 Weinheim, Germany
All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.
Print ISBN: 978‐3‐527‐35373‐6ePDF ISBN: 978‐3‐527‐83898‐1ePub ISBN: 978‐3‐527‐83899‐8oBook ISBN: 978‐3‐527‐83900‐1
Preface
Water contaminated with microorganisms is considered a primary transmitter of many fatal diseases, such as cholera, diarrhoea, dysentery, hepatitis A, typhoid, and polio, causing hundreds of thousands of deaths annually. The presence of chemical contaminants makes water unfit not only for potable purposes but also for other non‐potable uses. Water contamination is predominantly caused by dumping untreated sewage and industrial effluent into natural water bodies. Hence, it is mandatory to treat wastewater prior to its discharge to prevent degradation of the aquatic environment and safeguard public health. However, wastewater treatment is not stringently practised in many places as it involves substantial capital investment and requires a skilled workforce to ensure efficient operation. Moreover, the additional cost of handling and disposing of sludge coming out of a wastewater treatment plant makes the entire procedure even more taxing. Another significant issue with conventional wastewater treatment is the requirement of substantial energy to drive the treatment operation. Considering the rising global energy demand and dwindling fossil reserves, these energy‐expensive processes for wastewater treatment seem unsustainable and incongruous.
In recent years, microbial electrochemical technologies have emerged as a promising alternative for sustainable energy production and wastewater treatment. These technologies utilize microorganisms to convert organic matter and other compounds into electrical energy, hydrogen gas, and other valuable chemical products. At the same time, they can efficiently remove contaminants from wastewater and generate high‐quality water for reuse. Unfortunately, despite their unparalleled ability to recover bioenergy from wastewater, microbial electrochemical technologies have not received much appreciation beyond laboratories. Nevertheless, the advent of new materials and technological advancement can help to eradicate the inherent flaws of bioelectrochemical systems, which can fast track their commercialization. In fact, unveiling the immense potential of bioelectrochemically driven systems is the motivation behind the conceptualization of this book, titled “Microbial Electrochemical Technologies: Fundamentals and Applications.”
This book is a selective compilation of 26 chapters meticulously authored by recognized researchers and experts in the field of bioelectrochemistry, covering theoretical and practical aspects of these neoteric microbial electrochemical technologies. The first few chapters (Chapters 1–5) of the book focus on the fundamental principles of electrochemistry, including the types of fuel cells, their working principles, the role of catalysts, and insights into the biotic components of bioelectrochemical systems. Chapters 6–11 delve into an overview of the techniques used for the material characterization of synthesized catalysts in bioelectrochemical systems. This chapter elucidates the importance of characterization for catalyst optimization and discusses various techniques such as X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) analysis, and X‐ray photoelectron spectroscopy (XPS) that are essentially used in the field of electrochemistry.
The subsequent chapters (Chapters 12–18) elaborate on different types of bioelectrochemical systems and their configurations, including microbial fuel cells, microbial electrolysis cells, sediment microbial fuel cells, and microbial remediation cells. Chapter 19 covers the use of enzymatic fuel cells and biosensors for various applications. Chapter 20 discusses the photosynthetic microbial fuel cell, biophotovoltaic cell, and microbial carbon‐capture cell technologies. Chapter 21 introduces the modelling of bioelectrochemical systems, including system optimization and simulation techniques. Apart from the technical aspects, the book also covers the practical implementation of these technologies. It includes pilot‐scale case studies (Chapter 22), statistical analysis of performance (Chapter 23), and performance comparison with other wastewater treatment technologies (Chapter 24). The book also provides an overview of the circular bioeconomy implementation and life‐cycle assessment of bioelectrochemical systems (Chapter 25). Finally, Chapter 26 concludes the book with a discussion on the way forward and future directions for the field.
Overall, this book will serve as an essential reference for researchers, engineers, and students interested in microbial electrochemical technologies and their applications. All the knowledge domains required to understand bioelectrochemistry have been adequately covered in this book. Thus, it will serve as a good single reference material for new readers/scholars in this subject, and it can also be used as a text book where the subject “bioelectrochemistry” is being offered as an elective for the master's courses of chemistry/chemical engineering, energy science, environmental engineering, biotechnology, and materials science. We hope the book will rekindle interest in aspiring minds, ignite new ideas, and contribute to seminal research that can propel bioelectrochemical systems to industrial scale. This book is expected to bridge the knowledge gaps of this highly interdisciplinary subject and train future researchers in this subject domain making them abreast with the future direction of research. Thus, in the near future waste/wastewater shall be used as a fuel in field‐scale bioelectrochemical processes to recover energy or other value‐added chemicals to adopt circular economy model in waste/wastewater management.
Makarand M. GhangrekarIndian Institute of Technology Kharagpur, IndiaRao Y. SurampalliGlobal Institute for Energy, Environment and Sustainability, USATian C. ZhangUniversity of Nebraska‐Lincoln, USANarcis M. DuteanuTimisoara Polytechnic University, Romania
1Fuel Cells and Biofuel Cells
Anil Dhanda1, Shraddha Yadav2, Rishabh Raj2, Makarand M. Ghangrekar1,2, Rao Y. Surampalli3, Tian C. Zhang4 and Narcis M. Duteanu5
1Indian Institute of Technology Kharagpur, Department of Civil Engineering, Kharagpur 721302, West Bengal, India
2Indian Institute of Technology Kharagpur, School of Environmental Science and Engineering, Kharagpur 721302, West Bengal, India
3Global Institute for Energy, Environment and Sustainability, Lenexa, KS 66285, USA
4University of Nebraska‐Lincoln, Department of Civil and Environmental Engineering, College of Engineering, Scott Campus (Omaha), Lincoln, NE 68182, USA
5University of Politehnica, Faculty of Industrial Chemistry and Environmental Engineering, No. 6, Timisoara 300223, Romania
1.1 Energy Demand and Current Energy Scenario
The world is experiencing a catastrophic energy scarcity as the population of the planet approaches eight billion. Global energy consumption is rising continuously to meet the demands of this ever‐increasing population. The International Energy Agency (IEA) estimated a 4.6% rise in global energy consumption in 2021 due to a sudden boom in economic activities post‐COVID‐19 pandemic (IEA 2021). Further, the increase in energy demand is predicted to grow steadily over the next few decades, rising by 25% by 2040. Currently, fossil fuels, including coal, oil, and natural gas, meet the bulk (80%) of global energy demands (Moodley 2021). Out of which, coal contributes around 27%, natural gas 23%, and oil 32% of total energy (Moodley 2021). While non‐renewable fuels have been the primary energy sources for millennia, fossil reserves are limited and cause a number of adverse ecological impacts upon their extraction and usage. The combustion of fossil fuels liberates a high amount of CO2 into the atmosphere, which has escalated the problem of global warming and climate change. According to the Global Carbon Project estimate, CO2 emissions from fossil fuels reached a record high of 36.7 billion metric tonnes (Friedlingstein et al. 2022). This reflects the highest yearly growth since the Global Financial Crisis in 2008–2009 and an increase of 4.6% over the prior year in 2021 (Friedlingstein et al. 2022).
To reduce dependency on fossil‐derived energy and mitigate climate change, renewable energy sources, including solar, wind, geothermal, hydropower, and biomass, are gaining importance for energy production on a global scale. A number of factors drive the rising usage of renewable energy sources for power production, such as lowered instrument prices, technical improvements, and government policy. The IEA estimates that in 2020, renewable energy sources produced 29% of the world's power, up from 27% in 2019 (IEA 2021). Also, in 2020, the capacity of renewable energy sources increased by a record 280 gigawatts (GW). Among different renewable energy sources, solar‐ and wind‐based systems have recorded the fastest growth, with capacities increased by 127 and 111 GW in 2020 alone globally. The installed solar energy capacity increased from 50 GW in 2010 to over 760 GW in 2020 worldwide (IEA 2021). China is currently the largest producer of solar energy, with an installed capacity of over 240 GW as of 2020 (Hove 2020). While the United States, India, Japan, and Germany are the other players in the solar energy sector. Nevertheless, solar and wind energy are intermittent and susceptible to temporal and spatial fluctuations, making grid integration difficult.
Alternately, biomass energy is another renewable energy source that may be produced by various methods, including combustion, gasification, and anaerobic digestion. The most popular biomass energy is the bioenergy produced by burning organic materials like wood, agricultural waste, and plant stuff. In 2019, biomass energy contributed almost 10% of the world's primary energy supply (Popp et al. 2021). Hence, bioenergy has the potential to curb greenhouse gas emissions and contribute to the mitigation of climate change. The biogas and liquid or gaseous biofuels produced are the other categories of biomass energy. Biofuels are created by converting biomass into liquid fuels such as ethanol and biodiesel. In contrast, the anaerobic digestion of organic materials generates biogas. Although biomass energy is environmentally beneficial, it may cause land‐use change, competition with food production for land and resources, air pollution, and other environmental problems related to biomass burning.
Conventional renewable energy sources face several problems, including intermittent operation, temporal and geographical variations, land usage, and air pollution. To circumvent these limitations, electrochemical devices such as fuel cells can be one of the viable alternatives. Following their conception in 1889, fuel cells have been a central component of the alternative renewable source development, chiefly because of their simple operation, capability to oxidize different types of fuels, minimal or no environmental emissions, and smaller footprint than other renewable energy sources (Carrette et al. 2000). The flexible operation of fuel cells allows the use of different feedstocks as fuel to be converted into electricity via chemical reactivity. For instance, proton‐exchange membrane fuel cells (PEMFCs) utilize hydrogen as an energy source, whereas direct methanol fuel cells (DMFCs) are fed with methanol mixed with water. The fuel supplied is oxidized chemically to produce electricity. Fuel cells are different from batteries due to their continuous fuel requirement, whereas the fuel for batteries is already present in them. However, fuel cells have an advantage over batteries because the capacity of a battery is limited, and a periodic battery change/charge is required (e.g. batteries used in cell phones, smart watches, and calculators). In contrast, a fuel cell can continuously produce electricity as long as fuel is supplied, making them more reliable than traditional batteries.
Apart from the chemicals used as fuel, waste streams (liquid and solid) can be a credible renewable energy source and are hence often referred to as “misplaced resources” by many environmentalists. Recent technological advancements have made the recovery of resources from liquid/solid waste conceivable. However, wastewater generated from domestic, industrial, and agricultural activities is still treated conventionally, and the potential for energy recovery remains untapped. Worldwide, 380 billion cubic meters of wastewater is generated annually, which is expected to increase by 24% by 2030 and by 51% by 2050 (Qadir et al. 2020). Globally, wastewater treatment accounts for more than 2% of total energy usage. This energy is mainly used to aerate and mix wastewater, encouraging the development of microbes that decompose organic materials in the wastewater. In comparison, wastewater itself contains chemically stored energy. Thus, a system that can extract this energy as bioenergy and other valuable products is of great scientific interest.
In this regard, biofuel cells (BFCs), which operate on the same concept as traditional fuel cells, garner significant scientific interest. BFCs employ organic materials, such as glucose or other carbohydrates, as the source of chemical energy, while fuel cells use hydrogen, natural gas, or other fuels. In BFCs, the fuel is oxidized by enzymes or whole cells of microorganisms, which catalyse the conversion of organic matter into energy and by‐products such as water and carbon dioxide. A microbial fuel cell (MFC) is a prime example of such a system where the organic matter present in wastewater is used as fuel. The microorganism degrades the organic matter to produce electrons, protons, and CO2. Hence, MFCs can convert the chemical energy stored in wastewater to electrical energy, thus valorizing the wastewater, which is traditionally considered as a waste.
1.2 Fundamentals of Fuel Cells
A fuel cell is an electrochemical device that transforms chemical reactivity into electricity via electrochemical reactions. The term “fuel cell” was coined by two chemists, Ludwig Mond and Charles Langer, in 1889 while creating a fuel cell based on air (oxidant) and coal gas (fuel), respectively (Carrette et al. 2000). The core of the fuel cell consists of a unit cell having an electrolyte in contact with an anode and a cathode. The electrode material should have desired properties to catalyse the reduction (of oxidiser, e.g. O2) and oxidation (of fuel), both flowing through the fuel cell. Further, the electrons transfer via an external circuit from the anode to the cathode and generate electrical power. The first successful fuel cell application can be traced back to the late 1960s, during the NASA Apollo Space Program, where an alkaline fuel cell provided electricity and drinking water for the crew. Recent applications include power systems in cell phones, personal computers, power vehicles, and public transportation (Priya et al. 2022; Sajid et al. 2022).
Fuel cells are further categorized as galvanic/voltaic/Daniell and electrolytic cells. While the galvanic cell converts the chemical energy to electrical energy by spontaneous redox reactions, the electrolytic cell involves non‐spontaneous reactions. It requires an external energy source to drive the system. As galvanic cells can produce electricity, their applications vary from smart watches to calculators, cell phones, laptops, and power‐up engines. In contrast, the electrolytic cells can convert water to O2 and hydrogen and extract aluminium from bauxite. However, both cells have a similar configuration consisting of an anode chamber, a cathode chamber, and a solid electrolyte that separates the two electrodes. Fuel is supplied to the anode, while an oxidant (usually O2) is supplied to the cathode. At the anode, the fuel is oxidized, and electrons are released. The electrons flow through an external circuit to the cathode, reacting with the oxidant and protons to produce water and release energy.
The amount of energy that can be produced/required for different fuel cell types depends on the fuel (e.g. hydrogen, methanol, wastewater) and operating conditions, such as temperature and pH. The theoretical maximum electromotive force (Eemf), which is the voltage difference when no current is flowing through the circuit for any fuel cell, can be estimated by the Nernst equation (Eq. (1.1)).
where R stands for the gas constant (R = 8.314 J/mol K), the absolute temperature in Kelvin (K) is represented by T, n is the number of electrons transferred during the reaction, and F is Faraday's constant (F = 96 485 C/mol ≈ 9.65 × 104 C/mol). All equations are written according to the International Union of Pure and Applied Chemistry (IUPAC) convention. Under the standard conditions, a temperature of 298 K, chemical concentration of 1 M and 1 bar are taken for liquids and gases, respectively. Additionally, in BFCs, where microbes catalyse the reaction, the pH values are adjusted to neutral levels (pH = 7.0), which is similar to the pH level of the cytoplasm of most bacterial cells. E0 represents the standard cell electromotive force calculated with respect to hydrogen at standard conditions and termed as normal hydrogen electrode (NHE). It is measured by immersing a platinum electrode in a solution containing 1 N protons and bubbling pure hydrogen gas through the solution at 1 atm.
The Q in Eq. (1.1) represents the reaction quotient, which represents the ratio of the activity of products to the reactants and can be calculated as follows:
Considering any equation represented by Eq. (1.2):
for this reaction, Q is estimated as
where P, Q, R, and S represent the concentrations or partial pressure of different species involved in the reaction. To start with, assuming hydrogen is used as a fuel at the anode and O2 is used as a terminal electron acceptor at the cathode in a conventional fuel cell (Eq. (1.4)),
For the given reaction, Q can be estimated by Eq. (1.5).
The cell potential at the anode can be calculated as per Eq. (1.6), by inserting value of Q in Eq. (1.1).
where ′ represents the adjusted value at a pH of 7.0.
Similarly, on the cathodic side, the reaction occurring is represented by Eq. (1.7).
Hence Q became (Eq. (1.8))
The cathodic cell potential is estimated as per Eq. (1.9).
The standard potential of O2 () = 1.229 V and = 0.21 atm, and at a pH of 7.0, the cathode potential is given by Eq. (1.10).
Based on these individual potentials, the total cell potential can be estimated using Eq. (1.11).
In practical applications, hydrogen fuel cells may be operated at 80 °C (353 K), under pressurized conditions (2 bar), and at a pH of 3.0. The cell potential, in that case, can be computed by inserting these modified conditions in Eqs. (1.1)–(1.4), and it is equal to 1.24 V.
The same concepts of electrochemical fuel cells can be extended to bioelectrochemical cells. For instance, considering the example of an MFC utilizing acetate as a fuel source, the relevant equation is given by Eq. (1.12).
At neutral pH, the concentrations of reactants and products involved are 5 mM (HCO3−) and 16.9 mM (for 1 g/l CH3COO−) and E0 for acetate is 0.187 V. Using Eq. (1.1), the anode potential can be estimated as
As O2 is reduced on the cathodic side Ecat′ = 0.805 V as estimated earlier, hence the overall maximum cell potential for an MFC comes out to be 1.105 V. Additionally, instead of O2, other electron acceptors like ferricyanide can also be used at the cathode, which results in ECat′ = 0.361 V and Eemf′ = 0.361 − (−0.30) = 0.661 V (Logan et al. 2006).
In both hydrogen fuel cells and MFCs, the overall cell potential is positive, suggesting that both cells are galvanic cells proficient in generating electricity. Consider an example of a microbial electrolysis cell (MEC) using acetate as fuel. The relevant reactions are represented by Eq. (1.13) (anodic half‐cell reaction) and Eq. (1.4) (cathodic half‐cell reaction).
Again, using Eq. (1.1) the EAn′ = − 0.30 V as estimated in the case of MFC and using E0 for hydrogen as 0 V, the cathodic half‐cell potential can be calculated using Eq. (1.14).
For this case, the overall cell potential is −0.114 V (−0.414 V − (–0.30 V)), suggesting that it is an electrolytic cell and a minimum of −0.114 V of external voltage input is required for initiating hydrogen production. Using the same concept, the Eemf for other fuel cells/BFC can be estimated. The differentiation of a system for its ability to produce energy or consume energy can be easily understood by plotting anode and cathode potentials as portrayed in Figure 1.1. A positive slope (as observed in Figure 1.1) for any electro/bioelectrochemical system represents the galvanic cell (generating energy, i.e. MFC). In contrast, a negative slope indicates an electrolysis cell (i.e. microbial electrosynthesis [MES] and MEC), which requires energy to trigger the electrochemical reactions. A horizontal line indicates no external power is theoretically needed (i.e. hydrogen‐recycling electrochemical system); however, external energy may be necessary for practical cases to compensate for the losses incurred in the electrochemical system.
Figure 1.1 Anode and cathode potential in (bio)electrochemical system. HRES – hydrogen recycling electrochemical system; MEC – microbial electrolysis cell; MES – microbial electrosynthesis; MFC (Fe(CN)63−) – MFC with ferricyanide as electron acceptor; MFC (O2) – microbial fuel cell with O2 as electron acceptor; ORES – oxygen recycling electrochemical system).
1.3 Introduction to Fuel Cells and Biofuel Cells
As previously mentioned, fuel cells can use a variety of fuels as their energy source. Further, the fuel cells can be classified as chemical fuel cells (CFCs) or BFCs based on the reactions involved during energy conversion. The CFCs involve abiotic chemical reactions; in contrast, the BFCs use biological materials, such as enzymes and bacteria, to convert chemical energy into electrical energy. For example, PEMFCs utilize hydrogen as an energy source, whereas DMFCs are fed with methanol mixed with water. Likewise, BFCs use organic fuels, such as glucose and wastewater, catalysed by redox enzymes or microbes instead of inorganic catalysts used in CFCs.
Among CFCs, the PEMFC is the most prominent. It consists of a water‐based polymer membrane (acidic) as its electrolyte, a platinum‐coated anode, and a noble metal‐based cathode (Steele and Heinzel 2001). At the anode, hydrogen oxidizes to its ionic form, which transfers to the cathodic chamber via a membrane and produces water in reaction with O2 (terminal electron acceptor) in the cathodic chamber (aqueous vapour). Meanwhile, the generated electron travels via an external circuit towards the cathodic chamber, generating electricity. The O2 for the process can either be provided to the system artificially or utilized directly from the air. The PEMFC is considered a low‐temperature (85–105 °C) fuel cell, and it was the first to be used in space (Wang et al. 2020). Earlier prototypes used an unstable polystyrene sulfonate membrane, which was later succeeded by a highly conductive, robust Nafion membrane. Other categories (as shown in Figure 1.2) of CFC are high‐temperature proton‐exchange membrane fuel cell (HT‐PEMFC), DMFC, molten carbonate fuel cell (MCFC), phosphoric acid fuel cell (PAFC), solid oxide fuel cell (SOFC), and alkaline fuel cell (AFC) (Brandon et al. 2003; Wang et al. 2020).
Similar to CFCs, BFCs gained significant attention because of their exceptional combination of conventional fuel cells with an optimized biological environment. In the 1780s, the Galvani observed a frog's leg twitching on exposure to static current. This revolutionized the understanding of the central nervous system and emphasized the connection between biology and electricity (Bullen et al. 2006). Despite early discoveries, a microorganism‐based half‐cell was not demonstrated until 1911, when M.C. Potter observed electricity generation by liquid suspension of Escherichia coli and yeast. Then, Cohen, in 1931, demonstrated the successful generation of 35 V voltage from microbial BFCs connected in electrical series (Thomson and Brady 1963). Also, in the late 1960s, the BFC using a cell‐free enzyme system was implemented to supply power for a permanently implantable artificial heart (Bullen et al. 2006; Wingard et al. 1982).
Figure 1.2 Classification of chemical and biological fuel cells.
Conventional fuel cells depend on expensive catalysts to carry out redox reactions at electrodes to improve the overall performance of the fuel cell. On the other hand, the BFCs deploy biocatalysts (enzymes or whole microbial cell) to oxidize organic matter (such as alcohols, sugars, or organic acids) for the production of electrical energy via bioelectrochemical processes (Osman et al. 2011). The BFCs have the advantages of fuel flexibility, low cost, ease of operation, environmental friendliness, and can be operated in a mild environment (temperature range of 20–40 °C and at neutral pH). Organic fuel and oxidizer (aqueous solution) should be supplied in BFCs for efficient bioelectrochemical processes to ensure uninterrupted power production. However, an exceptional BFC, known as an “abiotic” BFC, relies on inorganic catalysts to oxidize bioorganic material compatible with biological systems (Tawalbeh et al. 2022). Further, the biologically catalysed devices can be divided according to the source of the biocatalyst, as described in Sections 1.3.1 and 1.3.2.
