Storage and fuel cells

Storage and fuel cells

1. Application of principles of electrode potentials to modern storage cells

   • Electrochemical cells are used as modern-day cells and batteries
     • Fuels cells: Cell reaction uses external supplies of fuel and an oxidant which are used up - cell will continue to run as long as there is fuel and oxidant available
     • Rechargeable cells: Chemicals react and provide electrical energy but the reaction can be reversed during recharging - reusable battery
       • Nickel+cadmium batteries used in rechargeable batteries
       • Lithium-polymer and lithium-ion batteries used in laptops
         • Benefits: Often found in home and can provide high levels of battery life
         • Disadvantages: Toxic when ingested and rapid discharge of current which can cause fires and explosions - restrictions on transport of lithium-based batteries and limited sales of the batteries to individual consumers in some countries
     • Non-rechargeable cells: Provide electrical energy until all the chemicals have reacted - battery becomes flat

2. Explanation that a fuel cell uses the energy from the reaction of a fuel with oxygen to create a voltage and the changes that take place at each electrode.

   • Modern fuel cells use hydrogen or hydrogen-rich fuels such as methanol
   • Fuel cells use energy from the reaction of a fuel with oxygen to create a voltage
     • Reactants flow in and products flow out while the electrolyte stays in the cell
     • They don't need to be recharged and can operate continuously as long as there is enough oxygen and fuel
   • 2H2O + 2e- <-> H2 + 2OH- (-ve) 0.5O2 + H2O +2e- <-> 2OH- (+ve)
     • More negative of the two systems is the negative terminal
       • Provides electrons
   • H2 + 0.5O2 --> H2O

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