John Watt, a PhD student at Victoria University of Wellington, describes how increasing the surface area of nanoparticles increases their performance as catalysts.
My research is looking into the synthesis of novel palladium nanoparticles basically to increase catalytic performance of palladium for things like catalytic converters in your car. What we want to do is be able to gain a control over the size and the shape of the nanoparticles, with the ultimate goal really of being able to have designable properties for these nanoparticles. The problem with nanoparticles as catalysts is that, once you get to the desired heat, you can get what's called nanoparticle agglomeration, which is essentially the nanoparticles will come together and melt. And obviously that's going to reduce your surface area, and that's going to reduce the amount of metal available to the target gas. So what Mazda have done is they have come along and they have made ceramic balls, and they have actually embedded the nanoparticles into the ceramic balls, so they are anchored, which means that they can't move around on the surface, they can't come together, and they can't melt, so everything is available to the target gas. So you can imagine if you've got a spherical nanoparticle embedded into the ceramic ball, you've only got half the shell available to the gas that it can come and sit on and do its chemical reactions.
What we do is we make nanoparticles of varying shapes and sizes. We can produce rods, or other various shaped particles, such as tripods. You could produce branch structures or something like that – it would start to look like trees coming out of the ceramic ball. So then you can increase the amount of metal available to the gas while still anchoring it in position. It’s going to increase the surface area, and it’s going to increase the catalytic performance.