A team of researchers at Brown University developed a composite catalyst using nitrogen-rich graphene dotted with copper nanoparticles. It was shown in a study that the new catalyst is able to efficiently and selectively convert carbon dioxide to ethylene, one of the world's most important commodity chemicals that is used to make plastics, construction materials and other products.
Chemical companies produce ethylene by the millions of tons each year using processes that usually involve fossil fuels. If excess carbon dioxide can indeed be used to make ethylene, like the results of this study imply, it could help make the chemical industry become more sustainable and eco-friendly. There is, however, much more work to be done before bringing such a process to an industrial scale.
The researchers experimented with copper nanoparticles deposited on several different graphene surfaces - pure graphene, graphene oxide and graphene doped with nitrogen in various forms. The study showed that seven-nanometer copper particles deposited on graphene doped with pyridinic nitrogen (an arrangement that causes nitrogen atoms to be bonded to two carbon atoms) had the best performance. That arrangement had selectivity for ethylene of 79%, significantly higher than other approaches, according to the study.
It seems to not entirely be clear what about the new catalyst is responsible for its performance, but the researchers proposed a few ideas. They estimate that it's probably a synergistic effect; The pyridinic nitrogen helps to anchor the copper nanoparticles and change the electronic environment around them, which changes the reaction pathway to selectively produce ethylene. Pyridinic nitrogen in the nitrogen-doped graphene forms a Lewis base center, which helps to draw more carbon dioxide close to the copper for the observed catalysis.
The researchers plan to continue work with the new catalyst, possibly using it in tandem with other catalysts to produce different reaction products.