Arthur J. Villasanta – Fourth Estate Contributor
Upton, NY, United States (4E) – Scientists have now proven that single nickel atoms are an efficient, cost-effective catalyst for converting carbon dioxide (CO2) into useful chemicals and usable energy.
Imagine if CO2 could easily be converted into usable energy. Now, scientists are one step closer to this difficult goal. Researchers at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory are part of a scientific collaboration that has identified a new electrocatalyst that efficiently converts CO2 to carbon monoxide (CO), a highly energetic molecule.
“There are many ways to use CO,” said Eli Stavitski, a scientist at Brookhaven and an author on the paper. “You can react it with water to produce energy-rich hydrogen gas, or with hydrogen to produce useful chemicals, such as hydrocarbons or alcohols. If there were a sustainable, cost-efficient route to transform CO2 to CO, it would benefit society greatly.”
Scientists have long sought a way to convert CO2 to CO, but traditional electrocatalysts can’t effectively initiate the reaction. That’s because a competing reaction, called the hydrogen evolution reaction (HER) or “water splitting,” takes precedence over the CO2 conversion reaction.
A few noble metals, such as gold and platinum, can avoid HER and convert CO2 to CO. These metals, however, are very rare and too expensive to serve as cost-efficient catalysts. To convert CO2 to CO in a cost-effective way, scientists used an entirely new form of catalyst. Instead of noble metal nanoparticles, they used single atoms of nickel.
“Nickel metal, in bulk, has rarely been selected as a promising candidate for converting CO2 to CO,” said Haotian Wang, a Rowland Fellow at Harvard University and the corresponding author on the paper. “One reason is that it performs HER very well, and brings down the CO2 reduction selectivity dramatically. Another reason is because its surface can be easily poisoned by CO molecules if any are produced.”
Single atoms of nickel, however, produce a different result.
“Single atoms prefer to produce CO, rather than performing the competing HER, because the surface of a bulk metal is very different from individual atoms,” said Stavitski.
Klaus Attenkofer, also a Brookhaven scientist and a co-author on the paper, added, “The surface of a metal has one energy potential–it is uniform. Whereas on a single atom, every place on the surface has a different kind of energy.”
In addition to the unique energetic properties of single atoms, the CO2 conversation reaction was facilitated by the interaction of the nickel atoms with a surrounding sheet of graphene. Anchoring the atoms to graphene enabled the scientists to tune the catalyst and suppress HER.
Based on the results from the studies at Harvard, NSLS-II, CFN, and additional institutions, scientists discovered single nickel atoms catalyzed the CO2 conversion reaction with a maximal of 97 percent efficiency. They said this is a major step toward recycling CO2 for usable energy and chemicals.
“To apply this technology to real applications in the future, we are currently aimed at producing this single atom catalyst in a cheap and large-scale way, while improving its performance and maintaining its efficiency,” said Wang.
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