Investigations shed light on a method for converting CO2 into sustainable fuel

An international research team comprising scientists from the School of Chemistry at the University of Nottingham, the University of Birmingham, the University of Queensland, and the University of Ulm has developed a material composed of copper bonded to nanocrystalline carbon nitride. The arrangement of copper atoms in a nanocrystalline structure facilitates the transfer of electrons from carbon nitride to CO2, a critical process in the solar-induced conversion of CO2 to methanol. The study has been published in the Royal Society of Chemistry's Sustainable Energy & Fuels Journal.

Photocatalysis utilises light to excite electrons within a semiconductor material, facilitating their passage through the material to react with carbon dioxide (CO2) and water. This reaction yields numerous valuable products, one of which is methanol, an environmentally friendly fuel. In spite of recent advancements, this procedure is inefficient and lacks selectivity.

The most significant contributor to global warming is carbon dioxide. While it is feasible to transform CO2 into valuable commodities, conventional thermal processes still depend on hydrogen that is derived from fossil fuels. It is critical to advance alternative methodologies that rely on photocatalysis and electrocatalysis, capitalising on the abundant and sustainable solar energy and water resources that are ubiquitous.

Dr Madasamy Thangamuthu, a research fellow in the School of Chemistry, University of Nottingham, who co-led the research team, said: "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."

Tara LeMercier, a PhD student who carried out the experimental work at the University of Nottingham, School of Chemistry, said: "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."

Professor Andrei Khlobystov, School of Chemistry, University of Nottingham, said: "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."

This innovation signifies a substantial progression in the comprehension of photocatalytic materials as they pertain to the conversion of CO2. This facilitates the development of catalysts that are both highly selective and tuneable, allowing for the manipulation of the catalyst at the nanoscale to precisely produce the desired product.

The EPSRC Programme Grant 'Metal atoms on surfaces and interfaces (MASI) for sustainable future' is providing funding for this research. The objective of this grant is to develop catalyst materials that facilitate the conversion of carbon dioxide, hydrogen, and ammonia, all of which are environmentally and economically critical. Producing the majority of the earth's abundant elements, including carbon and base metals, while ensuring the sustainable use of chemical elements without depleting rare element supplies, MASI catalysts are manufactured in an atom-efficient manner.

It is the mission of the University of Nottingham to promote environmentally friendly and sustainable technologies. In order to accelerate the development and deployment of innovation in green industries and advanced manufacturing, the East Midlands has established the Zero Carbon Cluster.

Journal Reference: Tara M LeMercier, Madasamy Thangamuthu, Emerson C Kohlrausch, Yifan Chen, Craig Stoppiello, Michael W Fay, Graham A. Rance, Gazi N Aliev, Wolfgang Theis, Johannes Biskupek, Ute Kaiser, Anabel E. Lanterna, Jesum Alves Fernandes, Andrei Khlobystov. Synergy of Nanocrystalline Carbon Nitride with Cu Single Atom Catalyst Leads to Selective Photocatalytic Reduction of CO2 to Methanol. Sustainable Energy & Fuels, 2024; DOI: 10.1039/D4SE00028E