Hydrogen

Hydrogen as a fuel

• Hydrogen is often seen as an environmentally friendly alternative to fossil fuels and biofuels.
• The only product of the combustion of hydrogen is steam.
• \(2H_2 + O_2 \rightarrow 2H_2O \)
• 

Disadvantages of using hydrogen as a fuel

• Producing hydrogen
• Currently, hydrogen is made by steam reformation of natural gas.
• This is a non-renewable resource.
• An alternative method of production is the electrolysis of water.
• Expensive
• Electricity used is usually made by burning fossil fuels
• 
• Bildunterschrift: This plant uses coal to produce hydrogen. However, it releases carbon dioxide and nitrous oxides into the atmosphere. These harmful gases contribute to global warming.

Disadvantages of using hydrogen as a fuel

• Safety
• Hydrogen is highly explosive as it is very reactive
• It must be compressed and chilled, then stored in tough, insulated tanks.
• It is not as convenient as petrol and diesel.
• 

Fuel cells

• Cells contain chemicals which react to produce electricity.
• The voltage produced by a cell is dependent upon a number of factors including the type of electrode and electrolyte.
• A simple cell can be made by connecting two different metals in contact with an electrolyte.
• Batteries consist of two or more cells connected together in series to provide a greater voltage.
• In non-rechargeable cells and batteries the chemical reactions stop when one of the reactants has been used up. Alkaline batteries are non-rechargeable.
• Rechargeable cells and batteries can be recharged because the chemical reactions are reversed when an external electrical current is supplied.
• Fuel cells are supplied by an external source of fuel (eg hydrogen) and oxygen or air.
• The fuel is oxidised electrochemically within the fuel cell to produce a potential difference.
• The overall reaction in a hydrogen fuel cell involves the oxidation of hydrogen to produce water.
• Hydrogen fuel cells offer a potential alternative to rechargeable cells and batteries.