Researchers at the University of Michigan developed a method to capture carbon dioxide and convert it into metal oxalates, which are used in cement production. They published their findings in Advanced Energy Materials.
The proposed carbon capture method. Image from University of Michigan.
Methodology: Lead catalyst
Previous research has shown that lead can be used as a catalyst to convert carbon dioxide into metal oxalates. However, this method typically requires large amounts of lead, an environmental and human health hazard.
Charles McCrory, associate professor of chemistry and macromolecular science and engineering, and his team at the Center for Closing the Carbon Cycle (4C) found that using polymers to control the microenvironment around the lead catalysts reduced the amount of lead needed to convert carbon dioxide.
The team used a set of electrodes to produce oxalate from carbon dioxide. At one electrode, carbon dioxide is converted to oxalate. The other electrode is a metal that is being oxidized and releasing metal ions, which bind with the oxalate ions and create a metal oxalate solid precipitate.
Once the carbon dioxide is converted into the metal oxalate solid, it won’t be released as carbon dioxide under normal conditions, said McCrory.
Why traditional cement production has a high environmental cost
According to the EPA, 92 cement plants reported emissions of 67 million metric tons of carbon dioxide equivalents in 2019, 10% of the industrial sector’s direct reported emissions.
The most common type of cement is Portland cement. The main ingredients are calcium, silicon, aluminum and iron. According to McCrory, producing this kind of cement has a high energy cost and a large carbon footprint. This is why he and his colleagues began looking into ways to mine carbon dioxide and convert it into materials that can be used to make cement.
Charles McCrory and the team
“This research shows how we can take carbon dioxide, which everyone knows is a waste product that is of little-to-zero value, and upcycle it into something that’s valuable,” said McCrory.
“It’s a true capture process because you’re making a solid from it,” he said. “But it’s also a useful capture process because you’re making a useful and valuable material that has downstream applications.”
“Metal oxalates represent an underexplored frontier—serving as alternative cementitious materials, synthesis precursors and even carbon dioxide storage solutions,” said Jesús Velázquez, a co-lead author of the study and associate professor of chemistry at UCD.
“In this work, we have an example of a trace lead impurity actually being a catalyst. I believe there are many more such examples in practice catalysis, and also that this is an underexplored opportunity for catalyst discovery,” said Anastassia Alexandrova, a co-lead author of the study and professor of chemistry and materials science at UCLA.
McCrory says the next steps will be to further study how to scale up the process, particularly the formation of the metal oxalate solid.
