Some Basic Concepts Related to Fuel Cells with an Emphasis

Report
Some Basic Concepts
Related to Fuel Cells
with a Focus
on Microbial and Enzymatic
Fuel Cells
Nevin Longenecker
John Adams High School
The PURPOSES of this
investigation were to

examine and evaluate variables associated with
increasing the efficiency of a microbial fuel cell .

propose and construct a prototype enzymatic fuel
cell based on the previous findings.

describe in an educational science journal an
inexpensive fuel cell which could be easily
constructed and used in a classroom. The
operation of such a cell would have diverse
applications in many sciences and would
integrate mathematical principles from calculus,
statistics, algebra and geometry.
Advantages of Fuel Cells
vs.
Internal Combustion Engines
 Unlimited
supply of fuel
 No reliance on foreign oil
 Little or no pollutants
 Much higher energy conversion %
 No moving parts
 No noise

Often Platinum Catalyst
V V

<-
Anode Chamber -->
Cathode Chamber
– Exposed to air
– Stores fuel

Membrane -^Allows for H+ passage
Microbial Fuel Cells
Procedures


A prototype microbial fuel cell was
designed and built. (next slide)
Factors affecting microbial fuel cell
efficiency were measured and evaluated.
– Surface area of electrodes
– Bacterial conc. on anode/in solution
– Aerobic vs anaerobic conditions
– Supplemental O2 sources
 Single and mixtures of enzymes were tested in
the prototype cell to compare power output.
Significant Factors Affecting
Microbial Fuel Cell Operation
Type of electrodes
 Surface area of electrodes
 Use of catalysts on electrodes and PEM
 Conc. of hydrocarbon in anode chamber
 Agitation of hydrocarbon molecules
 Rate of replacement of hydrocarbons
 Types of microbes/enzymes
 Conc. of microbes/enzymes

Examples of microbial-based fuel cells
Microbe
Substrate
Mediator
Anode
Voltage
E coli
Glucose
Methylene
Blue
Pt- C-cloth
625mV
Bacillus
subtilis
Glucose
Thionine
Vitreous
Carbon
640mV
E coli
Acetate
Neutral red Graphite
felt
250mV
550mV
Pseudomona Methane
s
methanica
1-Naphthol-2Sulfonate indo2,6
dichlorophenol
Pt-black
Proteus
vulgaris
Thionine
Carbon rod 350mV
Sucrose
Significant Factors Affecting
Microbial Fuel Cell Operation
 Types
of mediators
 Conc. of mediators
 Distance between electrode and PEM
 Type of proton exchange
membrane(PEM)
 Surface area of PEM
 Source of oxygen
 Temperature effects
Pseudomonas sp.
Mediator Shuttling Electrons
Types of Electrodes
Power Output C rod vs
C cloth -aerobic E coli
1.6
Cloth Elec
1.4
C Rod Elec
mWatts/cm2
1.2
1
0.8
0.6
0.4
0.2
0
0
5
10
15
Time Hrs
20
25
Carbon Rod and Carbon Fiber
Electrodes
Power Output of C rod Biofilm vs
C rod Solution –anaerobic Ecoli
180
160
C rod biofilm
Solution Bacti
mWatts/cm2
140
120
100
80
60
40
20
0
0
5
10
15
Time(hrs)
20
25
Proposed Advantages of Enzyme Use
1. Immediate contact with substrate
2. Elimination of metabolism of
substrate by bacteria
3. Elimination of possible mixing of
hazardous bacterial types
4. If immobilized on electrodes, no
mediators are required.
Immobilized Enzyme /Cathode
Interaction
Glucose Dehydrogenase
Partial Composition of PEB
Enzyme Solution
 Lipase
 Protease
 Amylase
 Hydrolase
 Likely-dehydrogenases,
lactase,
decarboxylase, invertase
 Supplied by Enzyme Solutions, Inc
PEB EnzymeTrial –anaerobic-C rod
3
2.5
watts/m2
2
1.5
1
0.5
0
0
10
20
30
40
Time(hrs)
50
60
70
PEB Trial C rod Cathode vs Pt Cathode
3
2.5
Trial #1 C Rod
Trial #2 Pt
Watts/m2
2
1.5
1
0.5
0
0
10
20
30
40
50
Time Hrs
60
70
80
90
100
Total Power Output in 22 hrs
Watts ( meter2)
2500
2000
1500
1000
500
0
0.56
1.11
2.22
4.44
PEB conc. pph anode solution
8.89
Long Term PEB Enzyme Action
4
3.5
3
Watts/m2
2.5
Watts/m2
2
1.5
1
0.5
0
0
20
40
60
Time -Hrs
80
100
120
PEB Investigation Trends and
Conclusions
1. Optimum power output developed in 2hrs
Whole Ecoli cells
PEB solution
0.2 watts/m2
2.1 watts/m2
2. Prolonged power output at 24 hrs
0.14 watts/m2 2.05 watts/m2
3. Prolonged optimum power output continued for 5
days.
4. Pt. coating on the anode did not improve the
efficiency of the enzymatic cell.
Uses for
Implantable Enzymatic Fuel Cells
(To utilize arterial glucose and oxygen with
immobilized enzymes on electrodes in a
noncompartmentalized cell)

Micropumps-insulin, pain meds, arthritis

Current for-nerve stimulation, hearing aids

Heart pacemaker (cells in series)
Immobilized Enzymes on
Electrodes
Implantable Arterial Fuel Cell
Additional Uses of
Enzymatic Fuel Cells
 Space-regeneration
of human waste
 Treatment of human waste in
developing countries
 Treatment of household wastes in
place of landfills
 Industry-detoxify chemical wastes
 Portable units- power generation
Acknowledgments
 University
of Notre Dame
 RET Program
 Dr. Alex Hahn
 Dr. Robert Nerenberg
 Dr. Valli Sarveswaran

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