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Dry Cell BatteryDry Cell Battery

Anode (-)Anode (-)

Zn ---> ZnZn ---> Zn2+2+ + 2e- + 2e-

Cathode (+)Cathode (+)

2 NH2 NH44++ + 2e- ---> + 2e- --->

2 2 NHNH33 + H + H22

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Nearly same reactions as in common dry Nearly same reactions as in common dry cell, but under basic conditions.cell, but under basic conditions.

Alkaline BatteryAlkaline Battery

Anode (-): Anode (-): Zn + 2 OHZn + 2 OH-- ---> ZnO + H ---> ZnO + H22O + 2e-O + 2e-Cathode (+): Cathode (+): 2 MnO2 MnO22 + H + H22O + 2e- ---> O + 2e- --->

MnMn22OO33 + 2 OH + 2 OH--

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Anode:Anode:Zn is reducing agent under basic Zn is reducing agent under basic conditionsconditions

Cathode:Cathode:HgO + HHgO + H22O + 2e- ---> Hg + 2 OHO + 2e- ---> Hg + 2 OH--

Mercury BatteryMercury Battery

44Lead Storage BatteryLead Storage BatteryAnode (-) Anode (-) EEoo = +0.36 V = +0.36 VPb + HSOPb + HSO44

-- ---> PbSO ---> PbSO44 + H + H++ + 2e- + 2e-Cathode (+) Cathode (+) EEoo = +1.68 V = +1.68 VPbOPbO22 + HSO + HSO44

-- + 3 H + 3 H++ + 2e- + 2e- ---> PbSO---> PbSO44 + 2 H + 2 H22OO

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Ni-Cad BatteryNi-Cad BatteryAnode (-)Anode (-)Cd + 2 OHCd + 2 OH-- ---> Cd(OH) ---> Cd(OH)22 + 2e- + 2e-Cathode (+) Cathode (+) NiO(OH) + HNiO(OH) + H22O + e- ---> Ni(OH)O + e- ---> Ni(OH)22 + OH + OH--

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HH22 as a Fuel as a Fuel

Cars can use electricity generated by HCars can use electricity generated by H22/O/O22 fuel cells.fuel cells.HH22 carried in tanks or generated from carried in tanks or generated from hydrocarbonshydrocarbons

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Hydrogen—Air Hydrogen—Air Fuel CellFuel Cell

Figure 20.9Figure 20.9

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Ballard Power SystemsBallard Power Systemshttp://www.http://www.ballardballard.com/.com/

Car using a HCar using a H22 fuel cell fuel cell

A HA H22-based fuel cell-based fuel cell

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Hybrid fuel car,Hybrid fuel car,page 847page 847