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What is a catalyst?

While Prof Richard Haverkamp, of Massey University, explains what catalysts are, Dr Aaron Marshall sets up a catalyst membrane for the electrolysis of water.


The standard definition that people learn at school is a catalyst is a substance that enables a reaction to take place, or speeds up a reaction without being consumed itself. So a reactions wants to take place, but it won"t take place unless there is something to trigger it and help it to go at a quicker rate or more easily. So that’s a very important aspect of a catalyst. But there is one other aspect that people don't seem to learn about so much, which is equally important. And that is that a catalyst enables a reaction to take place but can control the reaction pathway. The end product of most organic reactions with carbon based materials is carbon dioxide and water, but you don't often want carbon dioxide and water. You often want to take some starting materials and make some other interesting material that is of some value to you. And so if you have the right sort of catalyst you can control what the reaction is. It will determine what the products are from the reaction. So catalysts not only do they make reactions go faster and easier and at lower temperatures, but they enable a specific reaction to take place, so they can control the, the products of the reaction.