Option C5 By: Bassel, Yashar

C5.1 How does a Hydrogen Oxygen fuel work hydrogen and oxygen are bubbled through a porous carbon electrode into concentrated aqueous sodium hydroxide or potassium hydroxide. Hydrogen (the fuel) is fed into the anode compartment where it is oxidized.

C5.1 How does a Hydrogen Oxygen fuel work The oxygen is fed into cathode compartment where it is reduced. The diffusion rates of the gases into the cell are carefully regulated to get maximum efficiency. The net reaction is the same as burning of hydrogen and oxygen to form water.

C5.1 How does a Hydrogen Oxygen fuel work At anode              :  2 [ H2(g) + 2OH-] (aq) → 2H2O (I) + 2e- At cathode           : O2 (g) + 2H2O(I) + 4e-   →    4OH- (aq) Overall reaction  : 2H2 (g) + O2 (g)   →  2H2O (I)               

C5.1 How does a Hydrogen Oxygen fuel work Each electrode is made of porous compressed carbon containing a small amount of catalyst ( Pt, Ag or CoO ). This cell runs continuously as long as the reactants are fed. Fuel cells convert the energy of the fuel directly into electricity

C5.1 How does a Hydrogen Oxygen fuel work

C5.1 How does a Hydrogen Oxygen fuel work High efficiency : The fuel cells convert the energy of a fuel directly into electricity. Continuous source of energy : There is no electrode material to be replaced as in ordinary battery. The fuel can be fed continuously to produce power. Pollution free

C5.2 How does a rechargeable battery work? Rechargeable batteries behave like ordinary batteries when they are being discharged. In other words, an electrical circuit is created when one material oxidizes, or gives up electrons, while another material immersed in an electrolyte becomes reduced, or gains electrons.

C5.2 How does a rechargeable battery work? The key to a rechargeable battery, however, is that it can reverse this flow of electrons when it is plugged into an electrical outlet. The material that oxidizes during discharge gains electrons, while the other material gives up electrons

C5.2 How does a rechargeable battery work? Nickel-cadmium cell (NiCad) : Cd,Cd(OH)2|KOH|NiO2,Ni(OH)2,Ni Anode (-): grid covered with cadmium Cd(s)+2OH-(aq)----->Cd(OH)2(s)+2e- Cathode (+): grid covered with nickel(III)hydroxide NiO(OH)(s)+H2O(l)+e------>Ni(OH)2(s)+OH-(aq) Electrolyte: KOH Voltage: 1.25volts

C5.2 How does a rechargeable battery work? Anode (-): lead plates Pb(s)+HSO4-(aq) ----->PbSO4(s)+H+(aq)+2e- Cathode (+): lead plates covered with PbO2 PbO2(s)+3H+(aq)+HSO4-(aq)+2e- ----->PbSO4(s)+2H2O(l) Electrolyte: 4M H2SO4 Voltage: 2.1 volts per cell (6 cells in series makes up a 12volt car battery) Uses: motor vehicle batteries As cell delivers current, lead sulfate deposits on electrodes & [H2SO4] falls. Six 2V cells connected in series make up a 12V battery. To obtain high current output from the battery, the surface area of the electrodes in contact with the electrolyte must be large & the plates close together.

Option C5.3 What are the similarities and differences between a Hydrogen fuel cell and a rechargeable battery Fuel cells and batteries are similar because they use a chemical reaction to provide electricity. A battery stores the chemical reactants, usually metal compounds like lithium, zinc or manganese. Once used up, you must recharge or throw away the battery. A fuel cell actually creates electricity through reactants (hydrogen and oxygen) stored externally. The fuel cell will produce electricity as long as it has a fuel supply. In short, a fuel cell vehicle is refueled instead of recharged.