Imagine if carbon dioxide (CO2)—the primary cause of global warming—could be collected from smokestacks and turned back into fuel. Now, chemists report the discovery of a potentially cheap and stable catalyst that can efficiently split CO2 into carbon monoxide (CO), a molecular starting point for plastics, diesel, and jet fuels. Because renewable electricity can power these reactions, the catalyst could help make commodity chemicals without burning fossil fuels. It could also help create a market for the vast amounts of CO2 that companies are planning on capturing not just from smokestacks, but from the ocean and air.
“This is a major discovery,” says Jingguang Chen, a chemist at Columbia University. The catalyst is not the first or only compound that could help convert waste CO2 into more useful compounds. Still, because catalysts must prove themselves and scale up from prototype reactors in laboratories to commercial plants, every new catalyst is vitally important, says Cafer Yavuz, a chemist at the King Abdullah University of Science and Technology. “The problem is so big, there is room for everybody,” he says. “We need every chance we can get.”
Converting CO2 to CO is energy intensive because the bonds in CO2 are so stable. Companies are developing reactors that supply the energy needed to break those bonds by running at more than 1000°C. But generating those temperatures typically requires burning fossil fuels, leading to a large carbon footprint. And the best catalysts for these high-temperature reactions either contain expensive precious metals or degrade quickly.
In recent years, researchers have turned to inexpensive molybdenum-based catalysts that can do the job at only 500°C to 600°C. But so far they have either degraded too quickly or aren’t selective enough: Instead of producing pure CO, they also generate methane, a less useful chemical building block.
Today, chemists Milad Ahmadi Khoshooei and Omar Farha of Northwestern University report in Science the discovery of a molybdenum carbide compound that not only produces pure CO from CO2, but is highly stable. Khoshooei found that when he mixed simple table sugar with a molybdenum compound and baked it overnight at 120°C, he wound up with a structure that converted CO2 to CO with 100% selectivity in a small lab reactor running at just 600°C. The catalyst also remained unchanged after 500 hours of operation, a duration that Chen calls “very impressive” for an initial academic study.
The new molybdenum-based catalyst joins others on the mission to cheaply convert CO2 to CO. In 2020, for example, Yuvuz and his colleagues reported in Science that a nickel and molybdenum-based catalyst is able to convert CO2 and methane to CO and hydrogen gas, an industrially valuable combination known as synthesis gas. And in 2022, Matthew Kanan, a chemist at Stanford University and his colleagues reported in Cell Reports Physical Science that potassium and sodium carbonate catalysts efficiently convert CO2 and hydrogen gas to CO, a reaction more directly related to the new molybdenum catalyst.
Taken together, these CO2 conversion catalysts offer real hope for creating a circular economy where fuels critical for society are generated from atmospheric CO2, without the need for burning additional fossil fuels, says Matteo Cargnello, a chemist at Stanford. “They show,” he says, “how we can potentially make sustainable chemistry a reality.”
More: https://www.science.org/content/article/cheap-catalyst-could-help-turn-carbon-dioxide-fuels
