Last week my facebook feed nearly overflew with shares of an amazing discovery: a group of US scientists of the Oak Ridge National Laboratory in Tenessee had accidently stumbled upon a catalyst that turns CO2 into ethanol. For those of you unfamiliar with catalysts, they are materials or substances that speed up or slow down the rate of a chemical reaction by providing a ‘reactive site’. The catalyst itself is not altered during the process (don’t run away, the article won’t get more complicated than this ;) ).
Well well, I thought. It’s about the fourth or fifth time this year I read about a new technique to suck CO2 out of the air. This one sparked my interest more than previous discoveries, though. First of all, in this case the CO2 is turned directly into something useful –which could not be said of those Icelandic scientists who came up with an idea to turn CO2 into rocks we should bury under the ground. Secondly, the process to turn the CO2 into ethanol happens at room temperature. Why that’s so nice will become clear soon.
But let’s have a better look at the discovery first. What happened? The scientists were studying electrocatalysis, which refers to the process of speeding up chemical reactions by applying a voltage over the catalyst. The scientists initially wanted to create a graphene-based catalyst but didn’t succeed with the equipment available in the lab. Instead, they ended up with a catalyst with small carbon spikes, which happens to create a perfect reactive site for CO2. While the scientists were expecting methanol to come out of their experiment, they were happily surprised to find ethanol. Ethanol, that form of alcohol that is not only giving you a good night out, but also is used as a fuel for vehicles. In the US nearly all car fuels at the pump are a mix of gasoline or diesel and around 10-15% corn or sugar based ethanol.
One of the interesting things about the reaction is that the catalyst doesn’t require expensive rare earth metals like platinum. The only things you need are copper and carbon. In addition, the whole reaction of turning CO2 into ethanol happens at room temperature. That means that the conversion can be started up quickly and with nearly no additional activation energy. And that really gets me excited. Really.
C’mon Elias, how come? Let me explain. If this process can be started up so easily, it is very flexible and forms the perfect tool to do something useful with the excess renewable electricity from the wind and the sun on moments of oversupply –which are driving our electricity grid operators and energy markets crazy at the moment. When there is too much wind during the night when no-one needs it, we now might use it to turn the most important greenhouse gas into a fuel. Neat, don’t you think?
Now before we all go crazy –as some renewable energy fanatics and environmentalists did last week– two notes of caution. Despite the multitude of articles that present the discovery as something that soon could be applied on large scale, it will not. I took the time to actually read the paper published by the scientists and their conclusion is pretty clear: ‘The overpotential [this is an effect that limits the performance of the catalyst] …. probably precludes economic viability for this catalyst…’. Too bad. For now, a lot more research is needed before we can get to large-scale application of the technology.
Second reason for caution should be the following. That portion of my readers that is familiar with the energy field is probably reading this article with growing astonishment. Isn’t this what hydrogen was promised to do? Indeed, for several years hydrogen is studied to be used as a carbon-free energy carrier generated by excess renewable electricity. Just like ethanol, hydrogen requires not too much adaptations to integrate into our current energy systems. Where ethanol can be used as a fuel for cars, hydrogen can be mixed with natural gas to fuel power plants or warm water boilers. But after decades of development and research, hydrogen still hasn’t taken off.
On the other hand, hydrogen production requires expensive platinum catalysts where the new technology does not. Can the discovery of the US’ scientists offer a cheap alternative? Time will tell.