1. Batteries and Fuel Cells
Pgs
Batteries and Fuel Cells

2. How can we use galvanic cells in everyday life?
BATTERIES!!
Take galvanic cells and make them easier to carry around and use!

3. All batteries require electrical potential:Li Rb K
Cs Ba Sr Ca Na Mg Al Zn Cr Fe Ni Sn Pb Cu Hg Ag Au
Most reactive
What is electrical potential:
The “pressure” on electrons to flow from one electrode to the other in a redox reaction
Depends on the difference between the atoms being oxidized and reduced on the activity series
Measured in volts
Least reactive

4. Types of Batteries
Lead Storage Batteries Dry Cell Batteries

5. Dry Cell Batteries Advantage of this type of battery:
Small, efficient at producing energy, don’t contain a liquid
Anode = Zinc case
Solid Zn is oxidized at anode:
Zn (s)  Zn2+ + 2e-
Cathode = Graphite rod
NH4+ and MnO2 is reduced
Used in calculators, watches, flashlights
What makes an alkaline battery different?
Last longer because the Zn doesn’t corrode as quickly in the basic environment!

6. How does our lab from Friday link to corrosion?
Corrosion is the process of returning metals to their natural state
It’s a REDOX reaction!!
Fe (s) + O2 (g)  Fe2O3 (s)

7. LOTS of metals corrode, but not all of them corrode to the same extent:
Ex  Aluminum!!
Aluminum will be oxidized by the air
Al (s) + O2 (g)  Al2O3 (s)
A thin layer of Al2O3 will cover the metal and protect it from further corrosion

8. How can we protect these metals from corrosion?
The Mg will react instead of the iron…but why???

9. Lead Storage Batteries
Advantages of this type of battery:
Can work for several years in extreme temperatures
Provides a lot of voltage (12 V) for its size
RECHARGE themselves!!
Where do we use lead storage batteries?
IN CARS!!!

10. Lead Storage Batteries
Anode = metal lead
Cathode = lead (IV) oxide coated onto lead grids
Solution = H2SO4
Anode and cathode
are separated, so the
e- move through a wire
that provides an
electric current to run
the car
Reaction  Pb + H2SO4  PbSO4 + 2H+ + 2e-
Reaction  PbO2 + 2e- + 2H+  PbSO4 + 2H2O

11. So what about hydrogen fuel cells?
Fuel cells: galvanic cells in which a fuel substance undergoes oxidation which creates energy
Don’t have to be re-charged
Can be created so that no air pollutants are produced
Used to run the Apollo missions
Trying to find a way to use them in cars!

12. Hydrogen Fuel Cells Cathode compartment has oxygen gas
Anode compartment has hydrogen gas
Middle compartment a membrane that allows H+ to move to O2
Oxidation: 2H2 (g) +  4H+ + 4e-
Reduction: O2 (g) + 4H+ +4e-  2H2O (l)
Overall: 2H2 (g) + O2 (g)  2H2O (l)

13. Hydrogen Fuel Cells and Cars
Show fuel cell Nova science now video