Dr Richard Tilley of Victoria University of Wellington explains what catalytic converters are and the role of catalysts. He also outlines why different shapes of nanoparticles are useful.
DR RICHARD TILLEY
A catalytic converter is basically made from a kind of ceramic material, and on this ceramic material, we have small metal particles, and these metal particles are catalysts. So these metal particles are made from platinum. And as the gases pass over these metal particles, the gas molecules land on the surface of the platinum particles, and then they can react on that surface, and then as they leave your car exhaust, they shouldn't be toxic compared to when they came in. So, in particular, the gases that are the problems are carbon monoxide, which is highly toxic to humans, and you know, if we breathe a lot of carbon monoxide, it will kill us. And so particularly we want to convert the carbon monoxide into carbon dioxide, which isn't as toxic to humans. So the platinum particles help or promote this chemical reaction to occur on the platinum particle surface. They can weaken this carbon oxygen bond in the carbon monoxide, and then they can help the oxidation of the carbon monoxide to convert it into carbon dioxide.
The key problem with catalytic converters at the moment is only about 10% of the platinum particles in a catalytic converter are active. What we want to do is improve the amount of platinum particles which are active to save money, but also convert more of the waste gases, and that will be better for the environment as well. So when the gas molecules come down on to the platinum particles’ surface, certain surfaces of the platinum crystals are the most active. So what we want to do is to grow different platinum particles of different shapes, and these different shapes we want to have surfaces which are the most catalytically active surfaces exposed to the gases as they come in.