Microbial Fuel Cells for Renewable Energy - Characterization Study University of Notre Dame Civil Engineering and Geological Sciences Department Microbial Fuel Cells for Renewable Energy - Characterization Study Presented by: Jesus M Garcia Figueroa University of Puerto Rico at Mayaguez Mentor: Susan Dahlheimer Advisor: Dr. Robert Nerenberg P.E.

Introduction 90% of world’s energy is supplied by fossil fuels Non-sustainable Negative environmental impacts Need sustainable, environmentally-friendly energy sources Fuel cells are a promising technology Environmental Impacts: air pollution, acid rain, global warming)

Hydrogen Fuel Cell 2e-→ 2e- ↓ H2 H2O 2H+ + 2e- 2H+ ½O2 + 2H+ + 2e- H2 M H2 H2O H2 O2 2H+ + 2e- 2H+ ½O2 + 2H+ + 2e- Chemical Reaction: H2  2H+ + 2e- ½ O2 + 2H+ + 2e-  H2O 2H2 + O2 → 2H2O

Alternative Fuel Cells H2 is not readily available Organic wastes also contain energy: Common catalysts not effective Bacteria can catalyze electron transfer to anode Chemical Reaction: Wastewater + H2O  nH+ + yCO2 + ne- ½ O2 + 2H+ + 2e-  H2O Wastewater + O2 → 2H2O + CO2

Our Experimental Setup Voltmeter Cathode Anode O2 Pumping R Load Proton Exchange Membrane (PEM)

Objectives MFC Qualitative Characterization Proton Exchange Membrane (PEM) Characterization Cathode Chamber Characterization Anode Chamber Characterization

Cathode Characterization Experiments Cathode Electrode Characterization Cathode Oxidant Surface Area Size Electrode Thickness Surface Area Form Cathode Material Original (Planar Electrode) Rod Electrode Original (6x10)cm2 Double Half Original (Thin) Thick Electrode Original (Carbon) Platinum Original (Oxygen) Ferricyanide solution

Cathode Characterization Details Experiments included loads of 10 Ω, 100 Ω, 1 kΩ, 10 kΩ, 100 kΩ and 1 MΩ A data logger recorded V With V and R, current and power were calculated using Ohm’s (V = IR) and Watt’s (P = VI) Laws.

Proton Exchange Membrane Characterization Proton Exchange Membrane (PEM) Characterization Nafion PEM Ultrex PEM

PEM Characterization Details Both chambers of the MFC contained a buffer solution, one chamber had no O2, other was saturated with O2. Monitored O2 diffusion across two membranes with a dissolved O2 probe. Compared how O2 concentration changed as a function of time for two membranes.

Anode Chamber Characterization Anode and Anode Electrode Characterization Attached Bacteria Suspended Bacteria

Anode Characterization Details Anode with biofilm was removed from operating MFC and placed in new MFC. Fresh electrode placed in operating MFC with suspended growth Compared the two systems.

Results and Discussion

Instability Region

General Results and Discussion Open circuit voltage was not stable in all experiments. Higher resistances resulted in unstable voltages, therefore the mid-range resistance of 10K Ohms is used for comparisons as it resulted in large power production in all experiments. Voltage and current characterization show consistence with power characterization for all experimental comparison.

Cathode Results Size: Double surface area better than half better than original. Thickness: Thin is ~1.25x better than thick electrode. Surface Area Form: Rod increased power ~1.1x greater the planar electrode surface. Material: Pt electrode increased power ~5.5x. Oxidant: Performance with ferricyanide ~12.6x better than with oxygen.

Conclusion Cathode parameters affect power production Ultrex has lower O2 diffusion than Nafion Both attached and suspended growth contribute to electron transfer MFC technology a promising alternative energy source

Lab Pictures

Future Work Make Anode MFC Experiments (such like Glucose and wastewater instead as a acetate feed) and more. See other things such as bacteria growth and PEM Oxygen and Hydrogen diffusion coefficients. Try to discover and explain how MFC Single Chamber works.

Acknowledgements Thanks for: Susan Dahlheimer, Dr. Roberto Nerenberg P.E. and his Graduate students Dr. Valli Sarveswaran, Jennifer Forsythe and EMSI-REU Program University of Puerto Rico at Mayaguez -Dr. Jose A. Colucci Rios P.E. -Monica Ospinal Jimenez -Juan Carlos Flores Bryan Anderson