Fuel cells revision

Why do the 2 half reactions occur in seperate compartments?

It prevents direct contact between the oxidant and reductant

What are the 2 main functions of a salt bridge?

• Maintains the neutrality of the 2 half cells ; prevents the + charge accumulating at anode and - charge at the cathode

• Completes the circuit by creating an internal circuit

Primary cells

Cannot be recharged

Secondary cells

Can be recharged

Fuel cells

Function continuously

Why must electrodes be both conducting and porous?

Allows hydrogen and oxygen gas to come into contact with the ions in the electrolyte and allow for the half-reactions to occur at the surface

Function of catalysts

Enhance the rate of reaction and current produced

Advantages of fuel cells

• Convert chemical energy directly to electrical energy

• Can use a variety of fuels

• When hydrogen is used as a fuel, no GHG are released

Disadvantages of fuel cellls

• Require a constant fuel supply

• Expensive

• The hydrogen used to source the fuel cells is mainly sourced from fossil fuels

Equation for steam reforming in the presence of a nickel catalyst

CH4(g) + H2O(g) → CO(g) + 3H2(g)

Steam reforming in the presence of a copper or iron catalyst

CO(g) + H2O(g) → CO2(g) + H2(g)