An international team of researchers, including various universities from the UK and Germany, successfully found a way to convert CO2 into fuel, according to a study published in the Sustainable Energy & Fuels Journal of the Royal Society of Chemistry. The process involves shining sunlight on single atoms of copper on a light-activated material. The authors hope this will become a way to create new types of green fuel.
The authors designed a material made up of copper atoms anchored on nanocrystalline carbon nitride. This structure allows the copper to transfer from carbon nitride to CO2, an essential step in the production of methanol from CO2 with the help of solar energy.
During photocatalysis, light hits a semiconductor material to excite electrons. This enables the electrons to travel through the material and eventually react with CO2 and water, producing various valuable products, including green fuel methanol. Despite recent progress, efficiency is still poor.
To improve this reaction, the team devised a process of heating carbon nitride to a high degree of crystallinity, maximising the functional properties of this material. Using magnetron sputtering (a method to deposit atoms in a vacuum), they added atomic copper in a solventless process, promoting contact between the semiconductor and metal atoms.
“There is a large variety of different materials used in photocatalysis. It is important that the photocatalyst absorbs light and separates charge carriers with high efficiency. In our approach, we control the material at the nanoscale. We developed a new form of carbon nitride with crystalline nanoscale domains that allow efficient interaction with light as well as sufficient charge separation,” said Madasamy Thangamuthu, from the University of Nottingham.
“We measured the current generated by light and used it as a criterion to judge the quality of the catalyst. Even without copper, the new form of carbon nitride is 44 times more active than traditional carbon nitride. However, to our surprise, the addition of only 1 mg of copper per 1 g of carbon nitride quadrupled this efficiency. Most importantly, the selectivity changed from methane, another greenhouse gas, to methanol, a valuable green fuel,” added Tara LeMercier, also from Nottingham.
The authors believe this work is an important step towards a better understanding of photocatalytic materials in CO2 conversion. It opens the door for creating highly selective and customised catalysts where the end product could be controlled by changing the nanoscale catalyst.
“Carbon dioxide valorisation holds the key for achieving the net-zero ambition of the UK. It is vitally important to ensure the sustainability of our catalyst materials for this important reaction. A big advantage of the new catalyst is that it consists of sustainable elements – carbon, nitrogen, and copper – all highly abundant on our planet,” concluded Professor Andrei Khlobystov from Nottingham University.
LeMercier T, Thangamuthu M, Kohlrausch E et al. (2024) Synergy of nanocrystalline carbon nitride with Cu single atom catalyst leads to selective photocatalytic reduction of CO2 to methanol. Sustainable Energy Fuels, 2024,8, 1691-1703, https://doi.org/10.1039/D4SE00028E