[Audio] Hello everyone today I'm going to explain about this paper Enhanced Coulombic efficiency and power density of air-cathode microbial fuel cells with an improved cell configuration
Introduction: Microbial fuel cells generate electricity by breaking down organic matter using bacteria. Single-chamber air-cathode microbial fuel cells without proton exchange membranes have simpler designs and lower costs but face challenges like oxygen diffusion, leading to substrate wastage and lower Coulombic efficiency. Low power density is also a challenge caused by high internal resistance. This study focuses on improving Coulombic efficiency and power density using J-Cloth and a new design called Cloth Electrode Assembly.
Methods:
Configurations used:
Without J-Cloth (Control setup).
With one to three J-Cloth layers.
Single and double Cloth Electrode Assembly to reduce electrode spacing.
Setup:
Cylindrical chambers with carbon cloth electrodes, which are known for their high conductivity and porosity.
Substrate used: Acetate as an energy source.
Operation modes:
Batch mode: Fixed substrate is added, and the system runs until it's consumed. This mode is simple and works for short-term tests.
Continuous-flow mode: Substrate is continuously supplied, mimicking real-world conditions like wastewater treatment. This mode gives steady, long-term power output.
Key measurements:
Coulombic Efficiency, power density, and internal resistance.
Figure one
Standard microbial fuel cell (No J-Cloth, No proton exchange membrane): This is the baseline design where oxygen diffuses from the cathode to the anode, disrupting anaerobic bacteria and wasting the substrate. As a result, the Coulombic efficiency is low, and power density is limited.
Microbial fuel cell with J-Cloth: In this setup, a J-Cloth is added to the water-facing side of the cathode. This acts as a substitute for the proton exchange membrane, blocking oxygen diffusion and improving Coulombic efficiency. The J-Cloth reduces oxygen transfer without the high cost or resistance associated with proton exchange membranes.
Single Cloth Electrode Assembly: Here, the J-Cloth is sandwiched between the anode and cathode, effectively reducing the spacing between electrodes. This design minimizes internal resistance, leading to higher volumetric power density compared to the standard or single J-Cloth setup.
Double Cloth Electrode Assembly: This configuration uses two J-Cloth layers. The tighter electrode spacing further reduces resistance and maximizes power density while still preventing oxygen diffusion effectively. Figure 2: This figure shows how power density varies with current density in microbial fuel cells using different layers of J-Cloth.
Zero layers (Control): Without any J-Cloth, the microbial fuel cell achieved the highest power density of eighty watts per cubic meter. This is because there was no additional internal resistance, but oxygen diffusion wasn't controlled.
One layer of J-Cloth: When one layer of J-Cloth was added, the power density slightly reduced to seventy-one watts per cubic meter. The J-Cloth started controlling oxygen diffusion effectively, but internal resistance increased slightly.
Two layers of J-Cloth: With two layers, the power density decreased further to sixty-eight watts per cubic meter. At this point, the trade-off between oxygen diffusion reduction and increased resistance was noticeable.
Three layers of J-Cloth: Finally, with three layers, the power density dropped significantly to fifty-five watts per cubic meter. This is because the internal resistance became too high, negatively affecting performance.
Key Takeaways: The optimal number of J-Cloth layers is one or two, as they balance oxygen diffusion control and manageable resistance. Adding too many layers, like three, leads to diminishing returns because the internal resistance dominates. Figure 3: This figure compares the electrode potentials of the anode and cathode as current density increases, using the silver/silver chloride reference electrode with a potential of one hundred ninety-five. 

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[image] A close up of a document Description automatically generated

Name: Praveen M Student ID: 237325 Subject: Clean Energy Technology

Introduction. Microbial fuel cells generate electricity by breaking down organic matter using bacteria Single-chamber air-cathode MFCs without PEMs have simpler designs and lower costs but face challenges like: Oxygen Diffusion: Leads to substrate wastage and lower Coulombic Efficiency (CE) Low Power Density: Caused by high internal resistance This study focuses on improving CE and power density using J-Cloth and a new design called Cloth Electrode Assembly (CEA). 

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Microbial fuel cells generate electricity by breaking down organic matter using bacteria  Single-chamber air-cathode MFCs without PEMs have simpler designs and lower costs but face challenges like:  Oxygen Diffusion: Leads to substrate wastage and lower Coulombic Efficiency (CE)  Low Power Density: Caused by high internal resistance  This study focuses on improving CE and power density using J-Cloth and a new design called Cloth Electrode Assembly (CEA)

Methods. Configurations: Without J-Cloth (Control setup) With 1–3 J-Cloth layers Single and Double CEA to reduce electrode spacing Setup: Cylindrical chambers with carbon cloth electrodes (High conductivity, porosity) Substrate: Acetate as an energy source Operation Modes: Batch mode: Fixed substrate is added, and the system runs until it's consumed. Simple but works for short-term tests Continuous-flow mode: Substrate is continuously supplied, mimicking real-world conditions like wastewater treatment. Gives steady, long-term power output Measurements: Key Metrics: Coulombic Efficiency (CE), Power Density, and Internal Resistance. 

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Configurations:  Without J-Cloth (Control setup)  With 1–3 J-Cloth layers  Single and Double CEA to reduce electrode spacing Setup:  Cylindrical chambers with carbon cloth electrodes (High conductivity, porosity)  Substrate: Acetate as an energy source Operation Modes:  Batch mode: Fixed substrate is added, and the system runs until it's consumed. Simple but works for short-term tests  Continuous-flow mode: Substrate is continuously supplied, mimicking real-world conditions like wastewater treatment. Gives steady, long-term power output Measurements:  Key Metrics: Coulombic Efficiency (CE), Power Density, and Internal Resistance

Configurations of Microbial Fuel Cells (MFCs). (A) Standard MFC: No J-Cloth; oxygen diffusion affects anaerobic bacteria activity on the anode Results in lower Coulombic efficiency due to substrate loss (B) MFC with J-Cloth: J-Cloth layer on the cathode's water-facing side acts as a barrier Reduces oxygen diffusion, improving CE (C) Single CEA: J-Cloth is sandwiched between the anode and cathode Reduces electrode spacing, decreases internal resistance, and increases volumetric power density (D) Double CEA: Two J-Cloth layers create a compact configuration Further minimizes electrode spacing, maximizing power density. 

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Configurations of Microbial Fuel Cells (MFCs)

(A) Standard MFC:  No J-Cloth; oxygen diffusion affects anaerobic bacteria activity on the anode  Results in lower Coulombic efficiency due to substrate loss (B) MFC with J-Cloth:  J-Cloth layer on the cathode's water-facing side acts as a barrier  Reduces oxygen diffusion, improving CE (C) Single CEA:  J-Cloth is sandwiched between the anode and cathode  Reduces electrode spacing, decreases internal resistance, and increases volumetric power density (D) Double CEA:  Two J-Cloth layers create a compact configuration  Further minimizes electrode spacing, maximizing power density

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Fig. 1. Schematic of MFCs (A) without J-Cloth, (B) with J-Cloth, (C) with single CEA (cloth electrode assembly), and (D) with double CEAs

Effect of J-Cloth Layers on Power Generation. 90 80 70 60 50 0 40 0 30 20 10 02 04 06 Current Density (mA cm O layer | layer —O— 2 layers 08 Q). 

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Effect of J-Cloth Layers on Power Generation

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Fig. 2. Effect of J-Cloth layers on power generation of MFCs with 1.7 cm electrode spacing

0 Layers (No J-Cloth): Maximum Power Density: 80 W/m³ 1 Layer of J-Cloth: Power Density: 71 W/m³ 2 Layers of J-Cloth: Power Density: 68 W/m³ 3 Layers of J-Cloth: Significant drop to 55 W/m³ due to higher internal resistance Key Trend: Power density decreases as the number of J-Cloth layers increases Benefit of Reduced Power Density: Improves Coulombic Efficiency (CE) by minimizing oxygen diffusion, ensuring better substrate utilization and stable bacterial activity

Anode and Cathode Potentials vs. Current Density. 

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Anode and Cathode Potentials vs. Current Density

200
100
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—o— Cathode
Anode/J cloth
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Fig. 3. Anode and cathode potentials (vs. Ag/AgCl reference electrode, 195 mVvs. NHE) as a function of current density in MFCs with 1.7 cm electrode spacing

Reference Electrode: Ag/AgCl (195 mV vs. NHE) Observations: Without J-Cloth: Cathode potential drops steadily Anode potential increases due to oxygen interference With J-Cloth: Cathode potential decreases more sharply (better oxygen control) Anode potential stabilizes (improved bacterial activity) Insight:
J-Cloth enhances Coulombic Efficiency by stabilizing both electrodes

Effect of J-Cloth on Coulombic Efficiency. 70 10 02 0.4 0.6 O layer I layer 2 layers 3 layers 08 Current Density (mA crn*). 

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Effect of J-Cloth on Coulombic Efficiency

70
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Fig. 4. Effect of J-Cloth layers on the Coulombic efficiency of MFCs with 1.7 cm electrode spacing

0 Layers (No J-Cloth): CE starts low at 10% and increases gradually, peaking at ~35% at 0.8 mA/cm², indicating high oxygen diffusion and substrate wastage 1 Layer of J-Cloth: CE improves significantly, reaching ~60% at 0.6 mA/cm² and stabilizing thereafter, showing better oxygen diffusion control. 2 Layers of J-Cloth: CE peaks at ~70% at 0.6 mA/cm², representing the best balance between oxygen diffusion control and internal resistance. 3 Layers of J-Cloth: CE decreases slightly to ~65% at 0.6 mA/cm², as higher internal resistance offsets the benefits of oxygen diffusion reduction.

Power Density vs. Current Density for Single and Double CEAs. 

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Power Density vs. Current Density for Single and Double CEAs

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Fig. 5. Power density as a function of current density using MFCs with single CEA or double CEAs and different working volumes

Double CEA (2.5 mL):  Achieves the highest power density, peaking at ~620 W/m³ at 0.6 mA/cm² Single CEA (3 mL):  Moderate performance, with a maximum power density of ~300 W/m³ Single CEA (6 mL):  Lowest power density, peaking at ~150 W/m³ due to increased internal resistance  Double CEA improves power density significantly by reducing internal resistance and optimizing electrode spacing

Power Generation in Continuous-Flow Mode. 1200 1000 800 600 200 SOQ 700 loon 200 350 son 2000 5000 IOOOQ 10 15 Time (hour) 25. 

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Resistances Tested: Sequentially adjusted resistances from 1000 Ω to 20Ω 1000 Ω: Low power density (~200 W/m³) due to high resistance limiting current flow 50 Ω: Peak power density (~1000 W/m³), showing optimal resistance for maximum efficiency 20 Ω: Power density drops (~700 W/m³) due to overloading and increased internal losses Reset to 50 Ω: Power density stabilizes (~800 W/m³), demonstrating system resilience

Fig. 6. Power generation of the double CEAs MFC operated in a continuous-flow mode

Conclusion. Enhanced Coulombic Efficiency: Applying two layers of J-Cloth significantly improved Coulombic efficiency, achieving 71% compared to 35% in PEM-less systems High Power Density: Double CEAs in continuous-flow operation achieved a power density of 1010 W/m³, exceeding conventional setups by over 15 times Reduced Oxygen Diffusion: The J-Cloth minimized oxygen diffusion, crucial for enhancing microbial activity and efficiency CEA Configuration: Innovative Cloth Electrode Assembly (CEA) enabled reduced electrode spacing, low internal resistance, and optimized substrate utilization. 

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Enhanced Coulombic Efficiency: Applying two layers of J-Cloth significantly improved Coulombic efficiency, achieving 71% compared to 35% in PEM-less systems  High Power Density: Double CEAs in continuous-flow operation achieved a power density of 1010 W/m³, exceeding conventional setups by over 15 times  Reduced Oxygen Diffusion: The J-Cloth minimized oxygen diffusion, crucial for enhancing microbial activity and efficiency  CEA Configuration: Innovative Cloth Electrode Assembly (CEA) enabled reduced electrode spacing, low internal resistance, and optimized substrate utilization

Advantages: Cost-effective Design: Use of J-Cloth and carbon cloth for scalable, low-cost systems. High Efficiency: Enhanced bacterial activity and substrate utilization. Real-World Applicability: Suitable for renewable energy generation and wastewater treatment. Limitations: Internal Resistance: Adding excess J-Cloth layers increases resistance, reducing power output. Long-Term Stability: Requires further research for sustained performance.

Questions. Explain the role of J-Cloth in microbial fuel cells (MFCs) and how it enhances Coulombic efficiency? What are the advantages of Double Cloth Electrode Assemblies (CEAs) compared to Single CEAs in terms of power density and oxygen diffusion? Discuss the use of low-cost materials like carbon cloth and J-Cloth in this study. How do they contribute to the scalability of MFCs?. 

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Explain the role of J-Cloth in microbial fuel cells (MFCs) and how it enhances Coulombic efficiency?
 What are the advantages of Double Cloth Electrode Assemblies (CEAs) compared to Single CEAs in terms of power density and oxygen diffusion?
 Discuss the use of low-cost materials like carbon cloth and J-Cloth in this study. How do they contribute to the scalability of MFCs?

Praveen Clean energy class

Hello everyone today I'm going to explain about this paper Enhanced Coulombic efficiency and power density of air cathode microbial fuel cells with an improved cell configuration
Introduction: Microbial fuel cells generate electricity by breaking down organic matter using bacteria. Single chamber air cathode microbial fuel cells without proton exchange membranes have simpler designs and lower costs but face challenges like oxygen diffusion, leading to substrate wastage and lower Coulombic efficiency. Low power density is also a challenge caused by high internal resistance. This study focuses on improving Coulombic efficiency and power density using J-Cloth and a new design called Cloth Electrode Assembly.
Methods:
Configurations used:
Without J-Cloth (Control setup).
With one to three J-Cloth layers.
Single and double Cloth Electrode Assembly to reduce electrode spacing.
Setup:
Cylindrical chambers with carbon cloth electrodes, which are known for their high conductivity and porosity.
Substrate used: Acetate as an energy source.
Operation modes:
Batch mode: Fixed substrate is added, and the system runs until it's consumed. This mode is simple and works for short term tests.
Continuous flow mode: Substrate is continuously supplied, mimicking real world conditions like wastewater treatment. This mode gives steady, long term power output.
Key measurements:
Coulombic Efficiency, power density, and internal resistance.
Figure one
Standard microbial fuel cell (No J-Cloth, No proton exchange membrane): This is the baseline design where oxygen diffuses from the cathode to the anode, disrupting anaerobic bacteria and wasting the substrate. As a result, the Coulombic efficiency is low, and power density is limited.
Microbial fuel cell with J-Cloth: In this setup, a J-Cloth is added to the water facing side of the cathode. This acts as a substitute for the proton exchange membrane, blocking oxygen diffusion and improving Coulombic efficiency. The J-Cloth reduces oxygen transfer without the high cost or resistance associated with proton exchange membranes.
Single Cloth Electrode Assembly: Here, the J-Cloth is sandwiched between the anode and cathode, effectively reducing the spacing between electrodes. This design minimizes internal resistance, leading to higher volumetric power density compared to the standard or single J-Cloth setup.
Double Cloth Electrode Assembly: This configuration uses two J-Cloth layers. The tighter electrode spacing further reduces resistance and maximizes power density while still preventing oxygen diffusion effectively. Figure 2: This figure shows how power density varies with current density in microbial fuel cells using different layers of J-Cloth.
Zero layers (Control): Without any J-Cloth, the microbial fuel cell achieved the highest power density of eighty watts per cubic meter. This is because there was no additional internal resistance, but oxygen diffusion wasn't controlled.
One layer of J-Cloth: When one layer of J-Cloth was added, the power density slightly reduced to seventy one watts per cubic meter. The J-Cloth started controlling oxygen diffusion effectively, but internal resistance increased slightly.
Two layers of J-Cloth: With two layers, the power density decreased further to sixty eight watts per cubic meter. At this point, the trade off between oxygen diffusion reduction and increased resistance was noticeable.
Three layers of J-Cloth: Finally, with three layers, the power density dropped significantly to fifty five watts per cubic meter. This is because the internal resistance became too high, negatively affecting performance.
Key Takeaways: The optimal number of J-Cloth layers is one or two, as they balance oxygen diffusion control and manageable resistance. Adding too many layers, like three, leads to diminishing returns because the internal resistance dominates.
 
Figure 3: This figure compares the electrode potentials of the anode and cathode as current density increases, using the silver/silver chloride reference electrode with a potential of one hundred ninety five