Research illuminates the method for converting CO₂ into sustainable fuel

Researchers have made a breakthrough in transforming CO₂ into methanol, leveraging sunlight to activate single copper atoms positioned on a light-sensitive material.

This innovation heralds a new era for the production of eco-friendly fuels.

The collaboration involved experts from the University of Nottingham’s School of Chemistry, the University of Birmingham, the University of Queensland, and the University of Ulm, resulting in the creation of a novel material. This material consists of copper anchored onto nanocrystalline carbon nitride, with the copper atoms embedded within the nanocrystalline framework.

This configuration facilitates the transfer of electrons from carbon nitride to CO₂, a crucial step for synthesizing methanol from CO₂ with solar energy. The findings were detailed in the journal Sustainable Energy & Fuels.

In the process of photocatalysis, light is directed onto a semiconductor material, which excites its electrons. These activated electrons then migrate within the material to engage with CO2 and water, catalyzing the creation of various beneficial substances, including methanol—a type of eco-friendly fuel. However, despite advancements in this field, the process is hindered by inefficiencies and a lack of specificity in its outcomes.

Carbon dioxide stands as the most significant contributor to global warming. While it’s feasible to repurpose CO2 into valuable products, the conventional thermal techniques depend on hydrogen derived from fossil fuels. Thus, it’s crucial to explore and develop alternative approaches, such as photo- and electrocatalysis. These methods utilize the endless supply of solar energy and the widespread availability of water, representing a more sustainable and environmentally friendly solution.

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.”

The researchers developed a method that involves heating carbon nitride to achieve the desired level of crystallinity, thereby enhancing its functional properties for use in photocatalysis. Through a process called magnetron sputtering, they were able to deposit atomic copper directly onto the material without the need for solvents. This technique ensures close contact between the semiconductor and metal atoms, optimizing the efficiency of the photocatalytic reaction.

Tara LeMercier, a Ph.D. 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 valorization 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 breakthrough significantly enhances our grasp of photocatalytic materials for CO₂ conversion, paving the way for the engineering of catalysts that are both highly selective and modifiable. By finely tuning the catalyst at the nanoscale, it becomes possible to specify the output, offering precise control over the desired product’s synthesis.