Scientists from Indian Technological University in Roorkee, Dharmsinh Desai University and Maulana Azad National Institute of Technology created a new graphene-based catalyst allowing for converting carbon dioxide into valuable chemical products. This discovery brings us closer to creating technologies capable of simultaneous decrease of CO₂ content in the atmosphere and provision of highly-demanded hydrocarbons – from fuels to feedstock for plastics manufacturing.
Since long ago, the electrochemical reduction of carbon dioxide has been viewed as one of the most high-potential methods of its disposal. This process takes place under standard temperature and pressure, and electricity from solar panels or wind parks may be the source of energy for it. The result is receiving fuel or feedstock, thus rounding-out the carbon cycle.
Most of the available catalysts have one serious restriction: they generate primary products, such as carbon monoxide, formic acid or methane. However, it is much more difficult to synthetize polycarbonic compounds (ethylene or ethanol), which are of high demand in industry, because to do that you need not only to break the bonds in CO₂ molecule, but also to link two carbon atoms into one molecule overcoming high energy barrier.
To cope with this task, the scientists proposed a non-standard solution – to build-in individual atoms of copper into nitrogen-containing graphene matrix. In such material every atom of copper is working like an active center and is to the best of its abilities. To synthetize the catalyst, the researchers applied ions of copper on graphene-oxide surface, and after that exposed the received material to thermal processing in the presence of nitrogen-containing compound. It resulted in atoms of copper firmly fixing in the graphene structure and stabilizing in the form, which is the most suitable for the reaction.
Using modern analysis methods, such as electronic microscopy and ion-induced X-ray spectroscopy, the scientists confirmed that the atoms of copper were evenly distributed across the surface of the material being in the form, which is the most suitable for the catalysis. The centers, in which copper was bonded with two atoms of nitrogen, turned out to be of special importance – such nodes provided for high reactivity and selectivity of the process.
The electrochemical tests demonstrated impressive results. Under the voltage of just -0.8 V the efficiency of CO₂ conversion achieved 91%, 59% of which was ethylene – the key feedstock for modern chemical industry. When the majority of catalysts may be converted into simple compounds, the new material was capable of efficiently directing the reaction towards forming more complicated carbon-carbon bonds, which increases its practical value.
Computer simulation based on density functional theory confirmed the received results.
The catalyst also demonstrated high stability: even after 20 hours of continuous work its activity remained unchanged.
Hence, the development of the Indian scientists opens up wide horizons for energy and chemical industries converting carbon dioxide from a threat to climate into the most valuable resource.
