UK scientists have discovered a simple sunlight-driven process to transform plastic waste into hydrogen and other useful chemicals to disintegrate plastics and produce and conserve energy. The team has successfully experimented with a process named photoreforming.

‘We want to use non-recyclable waste and make something useful out of it. Plastic waste contains a lot of energy, and when you throw it away, you throw away energy. Even when using biodegradable plastics, and waste is not generated, the energy in that plastic is still lost,’ says Moritz Kuehnel of Swansea University.

Kuehnel together with Erwin Reisner, from the University of Cambridge, and other colleagues have devised a method that uses cadmium sulfide quantum dots as photocatalysts to degrade plastics.

The process, called photoreforming, is simple. The team drops the photocatalyst onto the plastic, then immerse the plastic in an alkaline solution. Irradiation with sunlight reduces water from the solution to hydrogen while the plastic polymers simultaneously oxidise to small organic molecules.

The group tested the system by photoreforming three common polymers; polylactic acid, polyethylene terphthalate and polyurethane. The results matched those of state-of-the-art hydrogen evolution photocatalysis systems that employed expensive sacrificial reagents.

To properly recycle plastics and transform them into new useable plastics requires pure and clean materials. Plastics contaminated with food or oil are almost impossible to recycle because the impurities interfere with the recycling process, but this is not a problem with Kuehnel’s approach.

‘One of the beauties of our photoreforming approach is that it is not very picky, it eats up anything that is in there,’ says Kuehnel. Therefore, this approach will also enable a cleaner recycling process for plastic waste.

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