Fuel Cells

• A fuel cell is a type of electrochemical cell which means that it converts energy between electrical and chemical. They convert the chemical energy of a fuel + oxygen into electrical energy that is used to power things.
• • A Hydrogen oxygen fuel cell combines hydrogen and oxygen to form water and lots of energy.
• The structure of a hydrogen-oxygen fuel cell

  • In the middle there is the electrolyte
  • On the left there is the negative anode
  • On the right there is the positive cathode (opposite to electrolysis)
  • They are connected by a wire to allow flow of electrons
  • trodes are made of porous carbon (lots of tiny holes + catalyst)
  • There is also the anode and cathode compartment which both have inlets
  • On the right hydrogen enters the anode compartment, and in the cathode compartment oxygen enters
  • Once the reaction is over all the water and heat will leave by the outlet of the cathode compartment
• How it works

  1. Hydrogen enters from left
  2. Its oxidised by the anode
  3. Each hydrogen atom loses an electron to be come a +ion
  4. The electrons pass around the wire to cathode
  5. Hydrogen ions move through electrolyte to cathode
  6. This means they can react with oxygen and combine to make water
  7. Yet there is a spare oxygen atom, so we need two sets to react with each oxygen molecule
  8. The water leaves the cell via the outlet
• Oxidation of Hydrogen, half equation:

  
• Reduction of oxygen, half equation:

  
• you can combine the oxidation of hydrogen and reduction of oxygen to get this equation:

  
• The electrical energy of the reaction comes from the movement of electrons through the wire at the top.
• As fuel enters the cell it becomes oxidised, which sets up a potential difference across the cell.
• Pros of fuel cells

  • Use them to replace polluting batteries and fossil fuels
  • Only need hydrogen and oxygen
  • Simple devices
  • Dont produce any waste
  • Last longer than batteries
  • Less polluting to dispose of
• Cons of fuel cells

  • Hydrogen is gas so takes way more space to store
  • Explosive when mixed with air, so storage is dangerous
  • Requires energy to make