Do you remember the content of A-level Chemistry regarding electrochemical cells? We will focus on fuel cell for now! 😊
Fuel Cell
- Work like battery, but they do not run down or need recharging.
- They produce electrcity and heat as long as fuel is supplied.
- A fuel cell consists of 2 electrode: anode and cathode, sanwiched around an electrolyte.
Hydrogen burns in air to form water: 2H2(g) + O2(g) ➔ 2H2O(l)
Small amounts of nitrogen oxides are also formed in a reaction between nitrogen and oxygen in the air at high temps.
How It Works:
- Two electrodes are separated by a
- membrane, which allows H+ ions to pass through but not H2 and O2 molecules.
- The electrons released by the reaction at the hydrogen electrode are used up at the O
2 electrode. The p.d. set up pushes electrons through the external circuit, where they do work.
- Anode: H
2 ➔ 2H+ + 2e-
- Cathode: 2H
+ + 2e- + 1/2O2 ➔ H2O
Commonly seen in Fuel Cell powered electric vehicle.
Methanol-based fuel cells
Methanol is highly flammable, poisonous liquid alcohol, made from non-renewable waste or agricultural waste or the chemical recycling of CO2. Much easier to store than hydrogen, doesn't need high pressures or low temps.
- Fuel cell operates between
- 90°C - 120°C and uses the oxidation of methanol on a catalyst layer to form CO2.
- Electrons are transported through an
external circuit from anode to cathode.
CH3OH(g) + 1½O2(g) --> CO2(g) + 2H2O(l)
- Waste products: water and carbon dioxide
- Efficiency is low
- because methanol can pass through the available membrane materials.
- Cannot power vehicles but are ideal for consumer goods
Ethanol-based fuel cell
Ethanol is produced by fermentation of sugar cane.
- Fuel cell: oxidation of ethanol using platinum-based catalyst (EXPENSIVE!)
- A
- polymer acts as an electrolyte. The charge is carried by H+ ions.
- The liquid ethanol is oxidised at the anode in the presence of water, generating CO
2, H+ ions and electrons.
- H+ ions travel through the electrolyte, react with oxygen from air and the electrons from the ext. circuit at the cathode forming H
2O.
References:
- https://www.researchgate.net/figure/Chemical-reactions-of-direct-methanol-fuel-cell-DMFC_fig1_232318194
- https://www.researchgate.net/figure/Chemical-reactions-of-direct-methanol-fuel-cell-DMFC_fig1_232318194
- https://www.sciencedirect.com/science/article/abs/pii/S0360319915027846
This is the end of the topic!! Well done!
Drafted by Cherry (Chemistry)