Sugar-based catalyst upcycles carbon dioxide

In a brand new Northwestern University study, the catalyst successfully converted CO₂ into carbon monoxide (CO), a very important constructing block to provide quite a lot of useful chemicals. When the response occurs within the presence of hydrogen, for instance, CO₂ and hydrogen transform into synthesis gas (or syngas), a highly invaluable precursor to producing fuels that may potentially replace gasoline.

With recent advances in carbon capture technologies, post-combustion carbon capture is becoming a plausible choice to help tackle the worldwide climate change crisis. But the way to handle the captured carbon stays an open-ended query. The brand new catalyst potentially could provide one solution for disposing the potent greenhouse gas by converting it right into a more invaluable product.

The study will likely be published within the May 3 issue of the journal Science.

“Even when we stopped emitting CO₂ now, our atmosphere would still have a surplus of CO₂ in consequence of commercial activities from the past centuries,” said Northwestern’s Milad Khoshooei, who co-led the study. “There is no such thing as a single solution to this problem. We’d like to cut back CO₂ emissions and find latest ways to diminish the CO₂ concentration that’s already within the atmosphere. We should always reap the benefits of all possible solutions.”

“We’re not the primary research group to convert CO₂ into one other product,” said Northwestern’s Omar K. Farha, the study’s senior writer. “Nevertheless, for the method to be truly practical, it necessitates a catalyst that fulfills several crucial criteria: affordability, stability, ease of production and scalability. Balancing these 4 elements is essential. Fortunately, our material excels in meeting these requirements.”

An authority in carbon capture technologies, Farha is the Charles E. and Emma H. Morrison Professor of Chemistry at Northwestern’s Weinberg College of Arts and Sciences. After starting this work as a Ph.D. candidate on the University of Calgary in Canada, Khoshooei now’s a postdoctoral fellow in Farha’s laboratory.

Solutions from the pantry

The key behind the brand new catalyst is molybdenum carbide, an especially hard ceramic material. Unlike many other catalysts that require expensive metals, akin to platinum or palladium, molybdenum is a cheap, non-precious, Earth-abundant metal.

To rework molybdenum into molybdenum carbide, the scientists needed a source of carbon. They found an inexpensive option in an unexpected place: the pantry. Surprisingly, sugar — the white, granulated kind present in nearly every household — served as a cheap, convenient source of carbon atoms.

“Day by day that I attempted to synthesize these materials, I’d bring sugar to the lab from my home,” Khoshooei said. “When put next to other classes of materials commonly used for catalysts, ours is incredibly inexpensive.”

Successfully selective and stable

When testing the catalyst, Farha, Khoshooei and their collaborators were impressed by its success. Operating at ambient pressures and high temperatures (300-600 degrees Celsius), the catalyst converted CO₂ into CO with 100% selectivity.

High selectivity implies that the catalyst acted only on the CO₂ without disrupting surrounding materials. In other words, industry could apply the catalyst to large volumes of captured gases and selectively goal only the CO₂. The catalyst also remained stable over time, meaning that it stayed energetic and didn’t degrade.

“In chemistry, it is not unusual for a catalyst to lose its selectivity after just a few hours,” Farha said. “But, after 500 hours in harsh conditions, its selectivity didn’t change.”

This is especially remarkable because CO₂ is a stable — and stubborn — molecule.

“Converting CO₂ will not be easy,” Khoshooei said. “CO₂ is a chemically stable molecule, and we had to beat that stability, which takes numerous energy.”

Tandem approach to carbon clean-up

Developing materials for carbon capture is a serious focus of Farha’s laboratory. His group develops metal-organic frameworks (MOFs), a category of highly porous, nano-sized materials that Farha likens to “sophisticated and programmable bath sponges.” Farha explores MOFs for diverse applications, including pulling CO₂directly from the air.

Now, Farha says MOFs and the brand new catalyst could work together to play a job in carbon capture and sequestration.

“In some unspecified time in the future, we could employ a MOF to capture CO2, followed by a catalyst converting it into something more useful,” Farha suggested. “A tandem system utilizing two distinct materials for 2 sequential steps may very well be the way in which forward.”

“This might help us answer the query: ‘What can we do with captured CO₂?'” Khoshooei added. “Without delay, the plan is to sequester it underground. But underground reservoirs must meet many requirements with a view to safely and permanently store CO₂. We desired to design a more universal solution that will be used anywhere while adding economic value.”

The study, “An energetic, stable cubic molybdenum carbide catalyst for the high-temperature reverse water-gas shift response,” was supported by the U.S. Department of Energy, the National Science Foundation and the Natural Sciences and Engineering Research Council of Canada.