Soft Shell Turtle Apalone ferox

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Soft Shell Turtle (Apalone ferox)
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Batteries Fuel Cells

• Dr. Smith
• 2007

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Redox Cell

• Physically separated oxidation and reduction
• Ion contact between electrodes
• Most often in liquid - mobile ions
• Spontaneous galvanic cell (battery or fuel
  cell)
• Non-spontaneous electrolysis cell

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Terminology
e-
Anode
Cathode
-

Oxidation
Reduction
Y gt Y e-
X e- gt X-
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Batteries

• Portable sources of electricity
• 2 main types
• Single use - many different designs
• Rechargeable - all have the requirement that all
  products and reactants are insoluble and remain
  where they are formed

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Lead Acid Battery

• Gaston Plante 1859
• Discharge
• Ox Pb SO4-2 gt PbSO4 2e-
• Red PbO2 4H SO4-2 2e- gt PbSO4
  2H2O
• Recharge
• Red PbSO4 2e- gt Pb SO4-2
• Ox PbSO4 2H2O gt PbO2 2e- 4H
  SO4-2

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Leclanche Cell

• Georges Leclanche 1866
• A wet cell consisting of a porous cup immersed in
  a NH4Cl solution
• Ox Zn gt Zn2 2e-
• Red 2MnO2 NH4 2e- gt Mn2O3 2NH3
  H2O
• Dry cell designed by Sakizo Yai in 1885, starch
  paste replaced ammonium chloride solution

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Alkaline Cells

• Demonstrated by Thomas Edison in 1901
• Practical design by Lewis Urry of Eveready in
  1949
• Ox Zn 2OH- gt ZnO H2O 2e-
• Red 2MnO2 H2O 2e- gt Mn2O3 2OH-

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Mercury Battery

• Ox Zn(Hg) 2OH- gt ZnO H2O 2e-
• Red HgO H2O 2e- gt Hg 2OH-
• Toxic mercury is environmental contaminant and
  most manufacturers have ceased production
• 1.35 v is normal potential. Silver oxide is 1.55
  v and for sensitive applications adaptors are
  available (MR-9)

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Silver Oxide Battery

• Ox Zn 2OH- gt ZnO H2O 2e-
• Red Ag2O H2O 2e- gt 2Ag 2OH-
• Same sized cans as many mercury batteries, and
  same voltage behavior.

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Lithium Battery

• Invented by Lewis Urry of Eveready in 1970
• Over 25 different lithium battery chemistries are
  available in both single-use and rechargeable
  designs

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Nickel-Cadmium Rechargeable

• Waldmar Jungner in 1899
• Discharge
• Ox Cd 2OH- gt Cd(OH)2 2e-
• Red 2NiO(OH) 2H2O 2e- gt 2Ni(OH)2
  2OH-
• Recharge reverses reactions

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Nickel Metal Hydride

• Depends on a hydrogen storage alloy like rare
  earth metal alloys, or transition metal alloys.
  Newer designs use carbon nanotubes
• Discharge
• Ox Alloy(H) OH- gt Alloy H2O e-
• Red NiO(OH) H2O e- gt Ni(OH)2 OH-
• Recharge reverses reactions

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Fuel Cells

• Invented 1838 by William Grove - originally
  called gas batteries
• 1889 Wright, Thompson, Mond, and Langer exhibited
  0.73 V model
• 1893 Ostwald described fuel cell chemistry
• 1900-1950s Baur, Bacon, Davtyan worked on
  cells. Bacon patented (1958) a design used by
  NASA

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Fuel Cell Chemistry

• Combustion reactions that are controlled and
  produce electricity
• Many fuels have been adapted to fuel cells
  (hydrogen, natural gas, ethanol, gasoline)
• Still produce CO2 but few other side products of
  environmental concern

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Types

• Alkali
• Molten carbonate
• Proton exchange membrane
• Phosphoric acid
• Solid oxide

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Alkali Fuel Cell

• KOH solution provides OH-
• Reduction 2H2O O2 4e- gt 4OH-
• Oxidation H2 2OH- gt 2e- 2H2O
• Normally operates above 100 oC
• Provides heat, electricity, and fresh water
• Electrodes are porous graphite with metal
  catalyst particles

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Alkali Fuel Cell
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Molten carbonate

• Molten sodium carbonate at 650 oC provides CO3-2
  for electrode contact
• Ox H2 CO3-2 gt 2e- H2O CO2
• Red O2 4e- 2CO2 gt 2CO3-2
• CO2 is collected at anode and piped to cathode
  for combination with oxygen

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Molten Carbonate
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Proton Exchange Membrane

• Ionic contact is through a proton permeable
  membrane forming water on the oxygen side
• Red O2 4e- 4H gt 2H2O
• Ox H2 gt 2H 2e-

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Phosphoric acid

• 35 phosphoric acid and 65 silica paste forms
  contact between the electrodes.
• Operates at 150 - 200 oC and is around 80
  efficient. Most large plants are of this design
• Phosphoric acid molecules transport hydrogen ions
  from anode to cathode

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Phosphoric Acid FC Reactions

• Red O2 4H3PO4 4e- gt 2H2O 4H2PO4-
• Ox H2 2H2PO4- gt 2e- 2H3PO4

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Solid Oxide

• Solid ZrO2 at 1000 oC is capable of transporting
  oxide ions from one side of the solid to the
  other.
• Ox H2 O-2 gt H2O 2e-
• Red O2 4e- gt 2O-2

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