Researchers design ‘highly selective’ catalyst that turns CO2 into green fuel

AN INTERNATIONAL research team has developed a copper-based material that can turn CO2 into methanol using sunlight.

Researchers from the University of Nottingham’s School of Chemistry joined forces with the University of Birmingham, and universities in Australia and Germany to create a new form of carbon nitride, a metal-free semiconductor that can efficiently facilitate the photocatalysis process that turns CO2 into green fuel.

Photocatalysis can be used to capture and store solar energy to produce fuels like hydrogen, methane, syngas, and methanol. However, research into photocatalytic CO2 reduction has shown that the process faces challenges in producing clearer reaction results and product selectivity.  

Using extreme heat, the team formed nanoscale domains of graphitic carbon nitride, a photocatalyst that has applications in medicine and water treatment, and created nanocrystalline carbon nitride.

From greenhouse gas to green fuel

Taking it a step further, the team added atomic copper to the new material by depositing it in a solventless process. The researchers found that the addition of copper increased the efficiency for photocatalysis.

Tara LeMercier, a PhD student from the University of Nottingham, School of Chemistry, said: “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.”

Recycling CO2 to make renewable methanol

The chemical industry is a major producer of CO2, emitting around 925m t/y in 2021. Reusing CO2 as feedstock in chemical production, known as CO2 valorisation, may help the industry rely less on fossil fuel sources and meet its decarbonisation goals.

Valorisation can be used to develop renewable methanol, which can cut CO2 emissions by 95% compared to conventional fuels.

Andrei Khlobystov, from the University of Nottingham, School of Chemistry, 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.”

Khlobystov said that the team are currently looking to improve the quantum efficiency of the process to obtain more product per number of photons of light. They are also interested in developing the catalyst towards the production of more complex products from CO2, including ethanol.

In terms of scaling the process, Khlobystov added: “We can take it to a pilot plant scale (up to 0.5 kg) in our laboratory. Beyond that, we would need to cooperate with chemical engineers to take it to the industrial scale.”