“Through photosynthesis, plants and some bacteria use energy from sunlight to turn carbon dioxide and water into useful organic chemicals.
Now researchers have developed a catalyst that can turn CO2 into ethanol and propanol when operating at voltages that solar cells could provide (Proc. Natl. Acad. Sci. USA 2017, DOI: 10.1073/pnas.1711493114).
This process of powering chemical synthesis via solar power, called artificial photosynthesis, could enable carbon-neutral fuels. In such a system, every molecule of CO2 emitted when a fuel is burned could be captured to make another fuel molecule. But developing catalysts that can recycle CO2 is challenging, says Peidong Yang, a chemist at the University of California, Berkeley.”
Using catalysts based on iron, copper, indium, and other metals, researchers have successfully transformed CO2 into single-carbon compounds, including carbon monoxide, formate, and methanol. Making multicarbon compounds directly has proved more difficult.
The team discovered this better catalyst by systematically studying the performance of different densities of copper nanoparticles on support structures made of various materials. Graduate student Dohyung Kim found the best catalytic performance when he covered carbon paper with about 45 µg of the copper particles per square centimeter of the paper.
Despite these fastidious efforts, Yang says the researchers are not yet sure why the catalyst works so well. The researchers observed that after seven minutes under reaction conditions, the spherical nanoparticles fuse into larger cubic ones, with an interface between copper, copper oxide, and carbon from the paper. The group is still investigating the mechanism, but they believe this interface is key to the structure’s catalytic activity. “We’ve finally identified a key active interface to produce two- and three-carbon compounds,” Yang says.