Pollution remediation with single atom catalysts
What can catalysts do about clearing up harmful chemicals? Carbon-fluorine bonds are some of the strongest in the world and they are found in lots of products that we use everyday like when frying food, a carbon-fluorine coating on the frying pan stops the food sticking. But the problem with these strong bonds is that we cannot break them so they are building up in the environment and some of these chemicals are really toxic.
Recently a group of researchers in the US have managed to make a new type of catalyst that could break down toxic carbon-fluorine components in materials and pollutants building up all around us. Katie Haylor spoke to Dr Eli Stavitski, from the Brookhaven National Laboratory who was involved in the project.
Eli - You might remember that ozone hole scare dating back to the 80s. The primary cause of this was so-called chlorofluorocarbons that were used in refrigerators and air conditioners. They were eventually banned and replaced by other materials containing fluorine which are less harmful to the ozone layer, yet they’re many times more potent as greenhouse gases compared to carbon dioxide.
The specific chemical we targeted in our work is used worldwide in coatings and the current contamination levels are truly troubling. And that, together with the carbon-fluorine bond being one of the strongest, really made us look for new ways to clean up this mess.
Katie - Okay. And what is the chemical that you've been looking at? Tell us a bit about it.
Eli - It’s a perfluorooctanoic acid. This is a long chain of carbon atoms all connected to the fluorine bonds used in many products that we encounter every day. In the process of preparing them there is a contamination arising from the process.
Katie - So what kind of products is it in?
Eli - This is used in firefighter’s foams, for the coatings on your pans and skillets. In the coatings that protect different products so it’s really widely used.
Katie - So do we have any reason to be worried about the non-stick pans then?
Eli - Oh no. The pollution occurs in the process of the preparation.
Katie - Oh, I see. Can they be harmful in any other ways?
Eli - The materials that contain carbon and fluorines, such as perfluorooctanoic acids and related compounds, are suspected that at the moment to cause cancer and reproductive effects and this is why the agencies around the world are looking at them to determine how harmful they are.
Katie - So there could be potential health impacts, as well as environmental impacts, and crucially, these bonds can’t easily be broken so these compounds are sticking around for a long time wherever they end up. Now you’ve been trying to tackle this problem haven’t you, so tell us about these catalysts, these so-called single atom catalysts?
Eli - Yes. We managed to find the means to break these carbon-fluorine bonds using single atom catalysts. Ultimately, you want your catalyst particles to be very small and this is because the reactions - catalytic reactions - occur on the surface of the catalyst, so you could make nanoparticles out of them. But, ultimately, you can go one step further and break them into single atoms. Breaking large pieces of catalysts brings about very unique properties. If you think about a golden ring on your finger, it’s as chemically inert as it goes, but when it’s broken into the pieces of a billionth of a metre it will turn over many chemical reactions at very high rates. The ultimate goal here is to arrive to a single atom because that’s how we will optimise our catalytic activity.
Katie - So you can take a metal that on a macro scale would be pretty inert, and by changing the scale at which you’re operating, the properties change?
Eli - That’s exactly correct. And the ability to break the catalyst into a single atoms brings about even more new functionalities and new useful properties.
Katie - What material are we using here?
Eli - In this work, we were using platinum which is a precious metal. Platinum breaks hydrogen molecules into atoms that are very very active and those atoms are those that cleave the carbon-fluorine bond. But, ultimately, there are many people on this planet right now working on single atom catalysts of all different metals.
Katie - So looking forward to the future then, what could these single atom catalysts do for us?
Eli - Oh, there are many processes, many emerging reactions where single atom catalysts show amazing activity. But the catalyst we developed, it still contains precious metals and we really have to look and to find the useful functions of abundant, less expensive materials such as iron, cobalt and such. But, ultimately, single atoms are not the final goal, we’re just starting to manipulate single atoms of different kinds, arranging them in ensembles of two, three or maybe more where each atom will perform its own unique function.
Katie - Wow! So it sounds like there’s a lot of potential then and a lot of work that still needs to be done?
Eli - Oh yeah. This field is in its infancy and I’m so looking forward to being a part of it.