Artificial photosynthesis to produce ethylene

24 Nov 2017. NUS chemists have developed a prototype device to produce ethylene from carbon dioxide and water using natural sunlight.

The use of artificial photosynthesis to produce chemicals and fuels from carbon dioxide (CO2) and water (H2O) is the holy grail of many researchers studying sustainable energy conversion. This reaction, when scaled up, can provide an alternative fuel source and reduce the amount of CO2 in the air. Unfortunately, CO2 is one of the most stable molecules known to mankind, and its conversion is an arduous and highly energy-intensive process. To overcome these challenges, NUS researchers have developed a prototype device which uses the electrical energy generated from solar panels to convert CO2 electrochemically into valuable products. Their prototype has converted CO2 and H2O to ethylene and multi-carbon alcohols, using natural sunlight as the only energy source. The facile transformation of CO2 to chemicals is made possible with the use of copper catalysts which was developed by the team.

The research team led by Prof YEO Boon Siang from the Department of Chemistry, NUS achieved an unprecedented 1.5% solar-to-ethylene energy efficiency (the total solar-to-carbon-fuels energy efficiency is 2.9%).  These figures-of-merit are comparable to the efficiency level of natural photosynthesis by plants (3% to 6%). This is also the first known report of ethylene being produced directly from CO2 and H2O with significant efficiencies using only solar energy. Ethylene is one of the most produced organic molecules in the world as it is the crucial starting material for the manufacturing of plastics. Current industrial production of ethylene employs steam cracking of saturated hydrocarbons at 750°C to 950°C, which translates to an enormous consumption of energy. The process, developed by the NUS team, takes place at room temperature and pressure, with only the use of benign chemical reagents.

Prof Yeo’s research team is now developing suitable catalysts which can be used in similar systems to produce liquid fuels such as ethanol from CO2 and H2O. “We believe that our work, which is a product of efforts for the last two years, will play a crucial role to address key challenges in the realisation of a scalable artificial photosynthesis system to produce clean fuels sustainably,” said Prof Yeo.

 

NUS scientists have developed a prototype "artificial photosynthesis" device that uses solar energy to produce ethylene from CO2 and H2O. From left: Ph.D. student Dan REN and Prof Jason Yeo.

 

Figure shows the custom-designed artificial photosynthesis device developed by the research team.

 

Reference

Ren D; Loo NWX; Gong L; Yeo BS*, "Continuous production of ethylene from carbon dioxide and water using intermittent sunlight" ACS SUSTAINABLE CHEMISTRY & ENGINEERING DOI: 10.1021/acssuschemeng.7b02110 Published: 2017.

 

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