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The Possibilities of Biological Fuel Cells. O 2. NO 3 -. Fe 3+. SO 4 2-. CO 2. CO 2. e -. H 2 O. N 2. Fe 2+. HS -. CH 4. Organic Carbon. Anode. Microbial Electricity Generation. CH 3 COO - + 2OH -  2CO 2 + 5H + + 8e -.

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Presentation Transcript
microbial electricity generation

O2

NO3-

Fe3+

SO42-

CO2

CO2

e-

H2O

N2

Fe2+

HS-

CH4

Organic Carbon

Anode

Microbial Electricity Generation

CH3COO- + 2OH- 2CO2 + 5H+ + 8e-

Microbial fuel cells are based on the recently identified ability of microorganisms to pass electrons directly onto the surfaces of electrodes during catabolic respiration.

slide3

Two-chambered (poised-potential) electrochemical cell

Reference electrode

H2O

Anaerobic

Gr

Gr

Ag

O2 + H+ + e-

Graphite working electrode:

Anode (oxidizing)

Graphite counter electrode:

Cathode (reducing)

Cation-selective membrane

slide4

Concept

Organic carbon

CO2

ESred

CO2

ESox

Organic carbon

Microorganisms catabolize organic electron donors producing electrons which are transferred onto the anode

Direct reduction

Graphite

Ag

Indirect reduction

slide5

Advantages of Biofuel cells

  • More efficient than turbine (~25%) or solar (~15%) electricity generation
  • Does not require substrate to be combustible
  • Does not require the use of toxic and expensive heavy metals or metalloids
  • Is not limited by the reactivity of the electron donor
  • Do not produce toxic endproducts
slide6

Potential Applications of Biofuel cells

  • Powering Monitoring Devices in Remote Locations
  • Powering Electronic Devices from Renewable Energy Sources
  • Decentralized domestic power source
  • Conversion of waste organic matter to electricity instead of methane
  • Conversion of renewable biomass to electricity instead of ethanol
  • Bioremediation of environmental contaminants

Improved efficiency

slide7

Crucial parameters of operational effectiveness

  • Bacterial metabolism
  • Bacterial electron transfer
  • Performance of the cation selective membrane
  • Intrinsic electrical resistance of the system
  • Efficiency of the cathode oxidation step

Biological

Physical

Chemical and Biological

slide8

Studies done to date have:

  • Investigated electricity generation under constant resistance (load) or constant voltage
  • Investigated electricity generation by pure cultures under a poised potential with glucose, lactate, benzoate, acetate, or H2 as the electron donor
  • Investigated microbial communities on the anode surfaces in sediment systems with either glucose or NOM as the electron donor
slide9

Redox E’o (mV)

2H+ + 2e- H2 -420

Ferredoxin(Fe3+) + e-  Ferredoxin(Fe2+) -420

NAD+ + H+ + 2e-  NADH -320

S + 2H+ + 2e-  H2S -274

SO42- + 10H+ + 8e-  H2S + 4H2O -220

Pyruvate2- + 2H+ + 2e-  lactate2- -185

FAD + 2H+ + 2e-  FADH2 -180

Fumarate2- + 2H+ + 2e-  Succinate2- +31

Cytochrome b(Fe3+) + e-  Cytochrome b(Fe2+) +75

Ubiquinone + 2H+ + 2e-  Ubiquinonered +100

Cytochrome c(Fe3+) + e-  Cytochrome c(Fe2+) +254

NO3- + 2H+ + 2e-  NO2- + H2O +421

NO2- + 8H+ + 6e-  NH4+ + 2H2O +440

O2 + 4H+ + 4e-  2H2O +840

slide10

Anodic chamber

Cathodic chamber

H2

0.5 O2

2e-

2e-

2H+

H2O

2H+

2H+

1

2

3

4

5

6

7

+840

mV

Over potentials/inefficiencies are associated with several different steps involved in the biological fuel cell

-320

-420

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