Ethylene from artificial photosynthesis

ETHYLENE has been produced from an integrated artificial photosynthetic device for the first time at ambient conditions.

Developed by a team from the National University of Singapore (NUS), the prototype used oxide-derived copper and iridium oxide as electrocatalysts to produce ethylene gas using only sunlight, CO₂ and H₂O.

A 31.9% faradaic efficiency of ethylene was achieved, based on the quantity of electrons generated from solar energy. The overall energy efficiency of solar-to-ethylene was also comparable to the level of energy efficiency of natural photosynthesis by plants.

“Our device not only employs a completely renewable energy source, but also converts carbon dioxide, a greenhouse gas into something useful. This could potentially close the carbon cycle,” said Jason Yeo Boon Siang, assistant professor at NUS’ SERIS department of chemistry.

More than 170m t of ethylene, the building block of polyethylene, was produced worldwide in 2015 – and demand is expected to exceed 220m t by 2020. Current production involves steam cracking of fossil fuels at 750–950°C, consuming lots of energy and emitting about 2t of CO₂ for every ton of ethylene. As such, there is a growing demand for a cleaner and more sustainable way of producing ethylene.

The team also incorporated a battery in the prototype device to attain stable and continuous production of ethylene, 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.

Moving forward, the team will continue to work on their device to scale up the production of ethylene as well as employ similar systems to produce liquid fuels such as ethanol and propanol.    

ACS Sustainable Chemistry & Engineering: http://doi.org/gb4hgt