Fuel Cells Flashcards
1
Q
What is a fuel cell?
A
An electrical cell supplied with fuel and oxygen, that uses energy from the reaction to produce electricity.
2
Q
How do hydrogen-oxygen fuel cells work?
A
- The electrolyte is usually an acid and the electrodes are often porous carbon with a catalyst
- Hydrogen goes in the negative anode and oxygen in the positive cathode (opposite to electrolysis)
- Hydrogen loses electrons and forms H+ ions (oxidation) and these ions move to the cathode
- Oxygen gains electrons at the cathode and then reacts with H+ ions to form water (reduction)
- The overall reaction is hydrogen + oxygen –> water
3
Q
What are the 3 advantages of using fuel cells in cars?
A
- Don’t produce as many pollutants.
- Rechargeable (though there is a limit to how many times they can recharge).
- Fuel cells store more energy than batteries.
4
Q
What are the 3 disadvantages of using fuel cells in cars?
A
- Hydrogen takes up lots of space as it is a gas.
- Hydrogen is explosive when mixed with water so hard to store safely.
- Making hydrogen requires electricity (which is usually generated through burning fossil fuels).
5
Q
What is the reaction at the cathode (positive electrode) in a hydrogen-oxygen fuel cell?
A
4H+ + O2 + 4e- ➔ 2H2O
6
Q
What is the reaction at the anode (negative electrode) in the hydrogen-oxygen fuel cell?
A
H2 ➔ 2e- + 2H+
7
Q
What is a commonly used electrolyte in hydrogen-oxygen fuel cells?
A
Phosphoric acid.
8
Q
What is the overall reaction in a hydrogen-oxygen fuel cell?
A
2H2 + O2 ➔ 2H2O
9
Q
What are the electrodes in fuel cells made from?
A
Porous carbon
