A chemical cell produces a voltage until one of the reactants is used up. In a hydrogen-oxygen fuel cell, hydrogen and oxygen are used to produce a voltage, and water is the only product.
fuel cellDevice that produces a voltage continuously when supplied with a fuel and oxygen. work in a different way than chemical cells. Fuel cells produce a voltageThe potential difference across a cell, electrical supply or electrical component. It is measured in volts (V). continuously, as long as they are supplied with:
a constant supply of a suitable fuelMaterial that is used to produce heat, like coal, oil or gas.
oxygen, eg from the air
The fuel is oxidiseChemical substances are oxidised by the addition of oxygen, removal of hydrogen or the removal of electrons. electrochemically, rather than being burned, so the reaction takes place at a lower temperature than if it was to be burned. Energy is released as electrical energy, not thermal energyA more formal term for heat energy. (heat).
Hydrogen-oxygen fuel cells
Hydrogen-oxygen fuel cells are an alternative to rechargeable cells and batteries. In a hydrogen-oxygen fuel cell, hydrogen and oxygen are used to produce a voltage. Water is the only product. The overall reaction in a hydrogen-oxygen fuel cell is:
hydrogen + oxygen → water
2H2(g) + O2(g) → 2H2O(l)
Electrode half equations - Higher
At the negative electrode: 2H2 + 4OH- → 4H2O + 4e-
At the positive electrode: O2 + 2H2O + 4e- → 4OH-
When you add these two half equations together, you get the following overall equation:
2H2 + 4OH- + O2 + 2H2O + 4e- → 4H2O + 4e- + 4OH-
The hydroxide ions, electrons and two H2O molecules will now cancel because they are on both
sides, leaving the overall equation:
