A team of researchers at the National University of Singapore (NUS, Singapore; www.nus.edu.sg) has developed a prototype device to produce ethylene from carbon dioxide (CO₂), water and sunlight. The novel method produces ethylene at room temperature and pressure using benign chemicals and renewable energy.

The current process for producing ethylene is based on the steam cracking of fossil fuels at very high temperatures. This consumes large amounts of energy and emits twice the amount of CO₂ for every tonne of ethylene produced.

Recognising the need for a more environmentally friendly route, NUS assistant professor Jason Yeo and his team designed a copper catalyst that could generate ethylene from readily available water and CO₂ when powered by electricity. They introduced the catalyst into an artificial photosynthesis system, which converts the CO₂ and water into ethylene using only solar energy. NUS said the total energy efficiency achieved for the system is comparable to natural photosynthesis in plants.

Yeo explained that the current rate of CO₂ emissions exceeds that of carbon capture, leading to a steady increase in the atmospheric concentration of the greenhouse gas. “Our device not only employs a completely renewable energy source, but also converts carbon dioxide into something useful. This could potentially close the carbon cycle,” he said.

The team also incorporated a battery in the device to enable a stable and continuous production of ethylene, which is a key challenge in artificial photosynthesis systems. The battery stores excess solar energy collected in the day to power the device at night or under low light, ensuring that operations are not interrupted by varying amounts of sunlight.

Moving forwards, the team will continue to work on scaling up and commercialising the device. They also hope to develop similar systems to produce liquid fuels such as ethanol and propanol.