Fuel Cells Flashcards
Equations involved in H fuel cell
2H2(g) –> 4H+(aq) + 4e-
O2(g) + 4H+(aq) + 4e- –> 2h2o(l)
2H2 + O2 –> 2H2O
How does a hydrogen fuel cell work?
Two electrodes are separated by a membrane which allows hydrogen through but not hydrogen and oxygen molecules.
The potential difference set up pushes electrons through the external circuit.
Where does the H come from?
Natural gas or electrolysis of water.
Both methods require energy and produce pollution
Where does methanol come from?
Made from either non-renewable fossil fuels or agricultural waste such as straw and other biomass. Also chemical recycling of carbon dioxide
Better than H fuel cell because?
Easier to store as doesn’t require high pressures or low temperatures.
It is a liquid between -97 and +65c
More energy in a volume of meth than H.
How does a meth fuel cell work?
Uses the oxidation of methanol on a catalyst layer to form co2.
Protons travel through the membrane.
Electrons are transported through external circuit from anode to cathode providing power.
Cons of meth fuel cells?
Efficiency is low because alcohol can pass through the membrane
How is ethanol produced?
Easily done by fermentation of sugar cane, wheat, corn or straw
How does ethanol fuel cell work?
A polymer acts as an electrolyte and the charge is carried by H+ ions.
Liquid ethanol is oxidised at the anode in the presence of water generating co2, H+ ions and electrons.
H+ travels through the electrolyte and reacts with oxygen and the electrons from the external circuit to form h2o.
Membrane used in methanol fuel cell?
Proton exchange membrane is often made from Nafion (polymer with ionic groups attached)
Temperature of a methanol fuel cell?
Operates between 90 and 120c.
Catalyst used in ethanol fuel cell?
Expensive platinum surface catalyst
