Using a cerium catalyst to capture CO2

Sep 23 2018

A new catalyst could capture and transform carbon dioxide – creating useful chemicals from a greenhouse gas.

Carbon dioxide is perhaps the most notorious of the greenhouse gases – contributing to global warming and indirectly causing extreme weather, drought, famine, and the melting of the ice caps. There’s no doubt that the vast quantities of carbon dioxide being pumped into the atmosphere by industrial activity, the burning of fossil fuels, and countless day-to-day activities are very harmful to the planet.

However Professor Polly Arnold from the University of Edinburgh points out that the gas also has lots of useful applications. "It could be used as a precursor to many valuable materials such as biorenewable solvents, plastics, and pharmaceuticals."

This means that if we could find a way to capture carbon dioxide and transform it into other types of molecules we could reduce the amount of the gas in the atmosphere, and produce useful chemicals in the process.

Professor Arnold’s team have studied a series of compounds for carbon capture based on the element cerium, which is naturally abundant, relatively cheap, and has low toxicity. Cerium can act as a catalyst in a range of chemical reactions. The compounds also include tethered N-heterocyclic carbenes – a type of molecule that also has catalytic properties. Combining two catalysts in one has enabled the team to study and tune a great number of possible reactions.

Using this system, the team believe they will be able to capture and store carbon dioxide, before transforming it into a more useful chemical and releasing it. "Understanding the system has also allowed us to extend the reactivity to other molecules that are chemically similar to carbon dioxide", explains Professor Arnold.

Professor Arnold explains why the team have focused on cerium compounds. "There is a huge push to move away from using the noble metals to make catalysts, but people have mainly studied the 1st row of the transition metals as their replacements. Although cerium is one of the ‘rare earth’ elements, this name is a misnomer. Cerium can be classed as earth-abundant, being more common than iodine, its chloride is about six times less toxic than that of iron, and it is a cheap by-product of the mining of technology critical rare earths such as neodymium. So we are keen to learn how to tame it and its other less-understood f-block neighbours, for sustainable chemical catalysis."

She points out that previous similar systems have required specialised, high pressure gas reactors, whereas this one works at atmospheric cheaper. "Ideally, the perfect system is cheap, energy limited, and can be used off-the-rack", she says. "We are really excited to see how this project unfolds."


Read the paper
Royal Society of Chemistry

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