University of Notre Dame Civil Engineering and Geological Sciences

Department

Microbial Fuel Cells for Renewable Energy - Characterization Study

Presented by:

Jesus M Garcia FigueroaUniversity of Puerto Rico at Mayaguez

Mentor: Susan Dahlheimer Advisor: Dr. Robert Nerenberg P.E.

IntroductionIntroduction

90% of world’s energy is supplied by fossil 90% of world’s energy is supplied by fossil fuelsfuelsNon-sustainableNon-sustainableNegative environmental impacts Negative environmental impacts

Need sustainable, environmentally-friendly Need sustainable, environmentally-friendly energy sourcesenergy sources

Fuel cells are a promising technologyFuel cells are a promising technology

Hydrogen Fuel CellHydrogen Fuel Cell

H2 O2

M

H2O

Chemical Reaction:

H2 2H+ + 2e-

½ O2 + 2H+ + 2e- H2O

2H2 + O2 → 2H2O

2e-→ 2e- ↓

H2

2H+ + 2e- ½O2 + 2H+ + 2e-2H+

Alternative Fuel CellsAlternative Fuel Cells

HH22 is not readily available is not readily available Organic wastes also contain energy:Organic wastes also contain energy:

Common catalysts not effectiveCommon catalysts not effective Bacteria can catalyze electron transfer to anodeBacteria can catalyze electron transfer to anode

Chemical Reaction:

Wastewater + H2O nH+ + yCO2 + ne-

½ O2 + 2H+ + 2e- H2O

Wastewater + O2 → 2H2O + CO2

Our Experimental SetupOur Experimental SetupVoltmeter

O2 Pumping

R Load

AnodeCathode

Proton Exchange Membrane

(PEM)

ObjectivesObjectives

MFC Qualitative Characterization

Cathode Chamber Characterization

Proton Exchange Membrane (PEM) Characterization

Anode Chamber Characterization

Cathode Characterization Cathode Characterization ExperimentsExperiments

Cathode Electrode Characterization

Surface Area Size

Surface Area Form

Cathode Material

1. Original (6x10)cm2

2. Double

3. Half

Electrode Thickness

1. Original (Thin)

2. Thick Electrode

1. Original (Planar Electrode)

2. Rod Electrode

1. Original (Carbon)

2. Platinum

Cathode Oxidant

1. Original (Oxygen)

2. Ferricyanide solution

Cathode Characterization DetailsCathode Characterization Details

Experiments included loads of 10 Experiments included loads of 10 ΩΩ, 100 , 100 ΩΩ, 1 k, 1 kΩΩ, 10 k, 10 kΩΩ, 100 k, 100 kΩΩ and 1 M and 1 MΩΩ

A data logger recorded VA data logger recorded VWith V and R, current and power were With V and R, current and power were

calculated using Ohm’s (V = IR) and calculated using Ohm’s (V = IR) and Watt’s (P = VI) Laws.Watt’s (P = VI) Laws.

Proton Exchange Membrane Proton Exchange Membrane CharacterizationCharacterization

Proton Exchange Membrane (PEM) Characterization

Nafion PEM

Ultrex PEM

PEM Characterization DetailsPEM Characterization Details

Both chambers of the MFC contained a Both chambers of the MFC contained a buffer solution, one chamber had no Obuffer solution, one chamber had no O22, ,

other was saturated with Oother was saturated with O22..

Monitored OMonitored O22 diffusion across two diffusion across two

membranes with a dissolved Omembranes with a dissolved O22 probe. probe.

Compared how OCompared how O22 concentration changed concentration changed

as a function of time for two membranes.as a function of time for two membranes.

Anode Chamber CharacterizationAnode Chamber Characterization

Anode and Anode Electrode Characterization

Suspended BacteriaAttached Bacteria

Anode Characterization DetailsAnode Characterization Details

Anode with biofilm was removed from Anode with biofilm was removed from operating MFC and placed in new MFC.operating MFC and placed in new MFC.

Fresh electrode placed in operating MFC Fresh electrode placed in operating MFC with suspended growthwith suspended growth

Compared the two systems.Compared the two systems.

Results and Results and DiscussionDiscussion

Cathode Size Comparison

0.0E+00

2.0E-03

4.0E-03

6.0E-03

8.0E-03

1.0E-02

1.2E-02

1.4E-02

1.6E-02

1 10 100 1000 10000 100000 1000000

Resistance (Ohms)

Pow

er (m

W)

Original (6x10)cm 2̂

Double Electrode

Half Electrode

Instability Region

Cathode Comparison

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

1 10 100 1000 10000 100000 1000000

Resistance (Ohms)

Pow

er (

mW

)

Original (Carbon Electrode + Oxygen)

Pt Electrode

Cathode Comparison

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

1 10 100 1000 10000 100000 1000000

Resistance (Ohms)

Pow

er (

mW

)

Original (Carbon Electrode + Oxygen)

Ferricyanide Solution

Pt Electrode

General Results and DiscussionGeneral Results and Discussion

Open circuit voltage was not stable in all Open circuit voltage was not stable in all experiments.experiments.

Higher resistances resulted in unstable Higher resistances resulted in unstable voltages, therefore the mid-range voltages, therefore the mid-range resistance of 10K Ohms is used for resistance of 10K Ohms is used for comparisons as it resulted in large power comparisons as it resulted in large power production in all experiments.production in all experiments.

Voltage and current characterization show Voltage and current characterization show consistence with power characterization consistence with power characterization for all experimental comparison.for all experimental comparison.

Cathode ResultsCathode Results

Size:Size: Double surface area better than half better Double surface area better than half better than original.than original.

Thickness:Thickness: Thin is ~1.25x better than thick Thin is ~1.25x better than thick electrode.electrode.

Surface Area Form:Surface Area Form: Rod increased power ~1.1x Rod increased power ~1.1x greater the planar electrode surface.greater the planar electrode surface.

Material:Material: Pt electrode increased power ~5.5x. Pt electrode increased power ~5.5x. Oxidant:Oxidant: Performance with ferricyanide ~12.6x Performance with ferricyanide ~12.6x

better than with oxygen.better than with oxygen.

PEM Diffusion Test Comparison

0

1

2

3

4

5

6

7

0 10000 20000 30000 40000 50000 60000 70000 80000

Time (s)

O2

(mg/

L)

Nafion PEM

Ultrex PEM

Suspended vs. Attached Bacteria Comparison

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

0.018

0.020

10 100 1000 10000 100000 1000000

Resistance (Ohms)

Pow

er (

mW

)

Attached Bacteria

Suspended Bacteria

ConclusionConclusionCathode parameters affect power Cathode parameters affect power

productionproductionUltrex has lower OUltrex has lower O2 2 diffusion than Nafiondiffusion than NafionBoth attached and suspended growth Both attached and suspended growth

contribute to electron transfercontribute to electron transferMFC technology a promising alternative MFC technology a promising alternative

energy sourceenergy source

Lab PicturesLab Pictures

Future WorkFuture Work

Make Anode MFC Experiments (such like Make Anode MFC Experiments (such like Glucose and wastewater instead as a Glucose and wastewater instead as a acetate feed) and more.acetate feed) and more.

See other things such as bacteria growth See other things such as bacteria growth and PEM Oxygen and Hydrogen diffusion and PEM Oxygen and Hydrogen diffusion coefficients.coefficients.

Try to discover and explain how MFC Try to discover and explain how MFC Single Chamber works.Single Chamber works.

AcknowledgementsAcknowledgements

Thanks for:Thanks for: Susan Dahlheimer, Dr. Roberto Nerenberg P.E. and his Susan Dahlheimer, Dr. Roberto Nerenberg P.E. and his

Graduate studentsGraduate students Dr. Valli Sarveswaran, Jennifer Forsythe and EMSI-REU Dr. Valli Sarveswaran, Jennifer Forsythe and EMSI-REU

ProgramProgram University of Puerto Rico at MayaguezUniversity of Puerto Rico at Mayaguez

-Dr. Jose A. Colucci Rios P.E.-Dr. Jose A. Colucci Rios P.E.

-Monica Ospinal Jimenez-Monica Ospinal Jimenez

-Juan Carlos Flores-Juan Carlos Flores Bryan AndersonBryan Anderson