Hydrogen cars use hydrogen as a fuel source instead of gasoline. Hydrogen can power a car through either combustion in an internal combustion engine or reaction with oxygen in a fuel cell to produce electricity. Major car companies are focusing on fuel cells because they are more efficient and cleaner than combustion engines. Water is the only byproduct of the fuel cell reaction. While zero emissions, hydrogen cars still face challenges in production, storage, and transportation of hydrogen fuel, as well as high costs.

1. Harnessing Hydrogen for Power: Hydrogen Cars Marisa Katz Hannah Lobingier

7. The Functions of Fuel Cells http://www.gm.com/company/gmability/edu_k-12/teachers/fuelcells.html#dl