Which way ahead for hydrogen cars?
Glossary
catalyst. A substance that increases the rate of a chemical reaction without actually undergoing any change itself.
element. A substance made up of only one type of atom. For more information see our Back to basics topic, Atoms and molecules.
fuel cell. A device that converts energy from chemical reactions directly into electrical energy. The simplest fuel cell 'burns' hydrogen in a flameless chemical reaction to produce electricity. In order to 'burn' the hydrogen a fuel cell needs a source of oxygen and this is usually obtained from air. The only by-product from this type of fuel cell is water.
For more information about fuel cells see Fuelling the 21st century (Nova: Science in the news, Australian Academy of Science).
nanotubes. Extremely small tubes made from pure carbon. For more information see IPE nanotube primer (Institut de Physique des Nanostructures, Switzerland).
photovoltaic (PV) cells. Also known as solar cells. A photovoltaic cell is made of thin wafers of two slightly different types of silicon. One, doped with tiny quantities of boron, is called P-type (P for positive) and contains positively charged 'holes', which are missing electrons. (Electrons are negatively charged particles that orbit the nuclei of atoms.) The other type of silicon is doped with small amounts of phosphorus and is called N-type (N for negative). It contains extra electrons. Putting these two thin P and N materials together produces a junction which, when exposed to light, will produce a movement of electrons – and that constitutes an electric current. Photovoltaic cells thus convert light energy into electrical energy.
Posted May 2001.