Scientists solve puzzle of converting CO₂ emissions to fuel

Toronto, ON – Every year, humans advance climate change and global warming by injecting about 30 billion tonnes of carbon dioxide (CO₂) into the atmosphere.

A team of scientists from the University of Toronto (U of T) believes they’ve found a way to convert all these emissions into energy-rich fuel in a carbon-neutral cycle that uses a very abundant natural resource: silicon. Silicon, readily available in sand, is the seventh most-abundant element in the universe and the second most-abundant element in the earth’s crust.

The idea of converting CO₂ emissions to energy isn’t new: there has been a global race to discover a material that can efficiently convert sunlight, carbon dioxide and water or hydrogen to fuel for decades.  However, the chemical stability of CO₂ has made it difficult to find a practical solution.

“A chemistry solution to climate change requires a material that is a highly active and selective catalyst to enable the conversion of CO₂ to fuel. It also needs to be made of elements that are low cost, non-toxic and readily available,” said Geoffrey Ozin, a chemistry professor in U of T’s Faculty of Arts & Science, the Canada research chair in materials chemistry and lead of U of T’s Solar Fuels Research Cluster.

In an article in Nature Communications published August 23, Ozin and colleagues report silicon nanocrystals that meet all the criteria. The hydride-terminated silicon nanocrystals – nanostructured hydrides for short – have an average diameter of 3.5 nanometres and feature a surface area and optical absorption strength sufficient to efficiently harvest the near-infrared, visible and ultraviolet wavelengths of light from the sun together with a powerful chemical-reducing agent on the surface that efficiently and selectively converts gaseous carbon dioxide to gaseous carbon monoxide.

The potential result: energy without harmful emissions.

“Making use of the reducing power of nanostructured hydrides is a conceptually distinct and commercially interesting strategy for making fuels directly from sunlight,” said Ozin.

The U of T Solar Fuels Research Cluster is working to find ways and means to increase the activity, enhance the scale, and boost the rate of production. Their goal is a laboratory demonstration unit and, if successful, a pilot solar refinery.

In addition to Ozin, collaborators on the paper include Le He, Chenxi Qian, Laura Reyes, Wei Sun and P.Y. Wong – Department of Chemistry, Faculty of Arts & Science; Abdinoor Jelle and Jia Jia – Department of Chemistry, Faculty of Arts & Science, and Department of Materials Science & Engineering, Faculty of Applied Science & Engineering; Kulbir Kaur Ghuman, Department of Materials Science & Engineering, Faculty of Applied Science & Engineering; Chandra Veer Singh – Department of Materials Science & Engineering and Department of Mechanical & Industrial Engineering, Faculty of Applied Science & Engineering; Charles A. Mims, Paul G. O’Brien and Thomas E. Wood – Department of Chemical Engineering & Applied Chemistry, Faculty of Applied Science & Engineering, and Solar Fuels Research Cluster; and Amr S. Helmy – Edward S. Rogers Sr. Department of Electrical & Computer Engineering, Faculty of Applied Science & Engineering.