Solar-powered conversion of CO2 and plastics into value-added products offers a potential sustainable route to a circular economy, but its simultaneous conversion into an integrated process is challenging. Scientists have developed a system that can convert plastic waste and greenhouse gases into sustainable fuels and other valuable products – using only the energy of the sun.

Scientists at the University of Cambridge created the system, the first solar-powered reactor that simultaneously converts two waste streams into two chemical products. The reactor converts carbon dioxide (CO2) and plastics into various products that can be used in various industries.

In experiments, CO2 was converted into syngas, a crucial component of sustainable liquid fuels, and plastic bottles into glycolic acid, a substance commonly used in cosmetics. By changing the catalyst used in the reactor, the system can be easily modified to yield different products.

To move towards a more sustainable, circular economy, it is crucial to convert plastics and greenhouse gases – two of the biggest threats to the environment – into usable and valuable products.

Professor Erwin Reisner from the Yusuf Hamied Department of Chemistry said: “Turning waste into something useful using solar energy is an important goal of our research. Plastic pollution is a huge problem worldwide, and often much of the plastic we throw in the bins gets burned or thrown into landfill.”

Subhajit Bhattacharjee, the co-first author of the article, said: “A solar-powered technology that can simultaneously help tackle plastic pollution and greenhouse gases could be a breakthrough in the development of a circular economy.”

Co-first author Dr. Motiar Rahaman said: “We also need something that’s tunable so you can easily make changes depending on the final product you want.”

The scientists created an integrated reactor with two different compartments: one for greenhouse gases and one for plastic. The reactor uses a perovskite-based light absorber, a viable replacement for silicon in next-generation solar cells.

The group created several catalysts that were incorporated into the light absorber. The final product could then be changed by changing the catalyst. Tests of the reactor revealed that it could convert PET plastic bottles and CO2 with high efficiency into various carbon-based fuels, such as CO, syngas or formate, in addition to glycolic acid. The rate at which the reactor developed by Cambridge produced these compounds was significantly higher than that of traditional photocatalytic CO2 reduction methods.

Rahaman said, “In general, CO2 conversion takes a lot of energy, but with our system you just shine a light on it and it starts converting harmful products into something useful and sustainable. Before this system, we had nothing that could selectively and efficiently make high-quality products.”

Bhattacharjee said: “What’s so special about this system is its versatility and tunability – we’re currently making fairly simple carbon-based molecules, but in the future we might be able to tune the system to make much more complex products just by catalyst.”

Magazine reference:

  1. Subhajit Bhattacharjee, Motiar Rahaman, et al. Photoelectrochemical conversion of CO2 to fuel with simultaneous plastics reforming. Nature Synthesis, 2023 DOI: 10.1038/s44160-022-00196-0