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New zero-net-carbon-technology advances carbon-dioxide-to-ethanol conversion

In a new study, scientists realize that mixing cesium, copper, and zinc oxide in a close-contact configuration catalyzes a reaction pathway that transforms carbon dioxide (CO2) into ethanol (C2H6O). The study is a significant step towards a nearly ‘green’ zero-net-carbon technology that efficiently converts carbon dioxide into ethanol.

The study conducted by an international collaboration is led by the U.S. Department of Energy’sEnergy’s (DOE) Brookhaven National Laboratory. It gives a roadmap to navigate this challenging reaction. Also, by using theoretical modeling and experimental characterization, the study offers a picture of the full reaction sequence.

Along with creating this new zero-net-carbon technology, scientists discovered why this three-part interface is successful. Hence, the study could guide developing a practical industrial catalyst for selectively converting CO2 into ethanol.

Study’sStudy’s corresponding researcher, Brookhaven chemist Ping Liu said, “There has been much work on carbon dioxide conversion to methanol, yet ethanol has many advantages over methanol. As a fuel, ethanol is safer and more potent. But its synthesis is very challenging due to the complexity of the reaction and the difficulty of controlling C-C bond formation. We now know what kind of configuration is necessary to make the transformation and the roles that each component plays during the reaction. It is a big breakthrough.”

Scientists created an interface by depositing tiny amounts of copper and cesium onto a surface of zinc oxide. They then studied the regions where the three materials meet by using an x-ray technique called x-ray photoemission spectroscopy.

The technique shows the change in the reaction mechanism for CO2 hydrogenation after the addition of cesium.

They used two theoretical approaches for further analysis: density functional theory and kinetic Monte Carlo simulation. The density functional theory calculations is a computational modeling method to investigate the structures of materials. On the other hand, the kinetic Monte Carlo simulation is a computer simulation to simulate the reaction kinetics.

One significant fact that scientists learned- cesium is a vital component of the active system. Without its presence, ethanol cannot be made. In addition, good coordination with copper and zinc oxide is also essential. But there is much more to learn.

Brookhaven chemist José Rodriguez, who participated in the work, said, “There are many challenges to overcome before arriving at an industrial process that can turn carbon dioxide into usable ethanol. For example, there needs to be a clear way to improve the selectivity towards ethanol production. A key issue is to understand the link between the nature of the catalyst and the reaction mechanism; this study is on the front lines of that effort. We are aiming for a fundamental understanding of the process.”

In the future, scientists aim to find an ideal catalyst for CO2 conversion to “higher” alcohols, which have two or more carbon atoms (ethanol has two).

Journal Reference:
  1. Xuelong Wang, Pedro J. Ramírez et al.Cesium-Induced Active Sites for C–C Coupling and Ethanol Synthesis from CO2 Hydrogenation on Cu/ZnO(0001̅) Surfaces. DOI: 10.1021/jacs.1c03940

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