Solar reactor turns plastic pollution into clean hydrogen at ‘real-world scale’

Sunlight has been used to turn plastic waste into hydrogen “at a scale large enough to be genuinely useful” thanks to a new reactor, according to its developers.

The researchers, from the University of Cambridge, previously demonstrated that a solar-powered reactor could convert plastic into hydrogen and other valuable industrial chemicals. That demonstration was only at laboratory scale, however, with a catalyst measuring 25cm².

Now the team say they have “shown a clear path for converting this technology to a commercial scale”, in outdoor, real-world conditions. The new device is significantly larger – about 1m² – and was tested under natural sunlight outside Cambridge’s Department of Chemistry.

Instead of generating electricity like a conventional solar panel, the device drives a chemical reaction that converts waste into useful products while converting water to release clean hydrogen.

Earlier versions of the solar-powered panels required high temperatures, harsh chemicals or complicated manufacturing processes. Typically, this involved small particles suspended in solution and deposited on to a substrate.

“When we started trying to scale this technology up, we quickly found out that what seems simple on a small scale is not simple at all when you’re trying to make it at scale,” said co-first author Ariffin Bin Mohamad Annuar from Cambridge’s Yusuf Hamied Department of Chemistry. “We can’t really have giant vats of solution to make these panels – it’s just not practical at scale.”

The new panels can be assembled at room temperature without specialist equipment. First the light-absorbing material is sprayed onto a glass panel, then the panel is coated with specially designed molecules containing cobalt and zirconium.

“If we’re really going to change the way we deal with the twin problems of plastic pollution and clean energy generation, we’ve got to develop a very scalable way to make these photocatalyst materials and reactors – and show that they really work outdoors,” said Professor Erwin Reisner, who led the research.

Co-author Professor Dominic Wright’s team, also from the Department of Chemistry, made the molecular precursor material. Those precursors were then loaded into a sprayer, which was applied directly to a glass panel.

“What surprised me was, after all the optimisation, just how simple it is,” said Mohamad Annuar. “We just have this huge panel, we spray our catalyst on it, put it into our solution, put it under the sun, and it produces hydrogen and other valuable chemicals just from plastic waste. It’s just simple and scalable.”

The researchers showed the reactor works on materials ranging from cellulose to PET plastic bottles used for fizzy drinks. They also carried out a cost analysis to show what it would realistically take to scale the technology up commercially, which they said is a first for this type of research.

While the spray-coating method reportedly reduces the cost to produce the reactors, the researchers said they still need to improve the durability and efficiency of the reactors before they are ready for commercial production.

A patent for the technology has been filed with Cambridge Enterprise, the university’s innovation arm. The research was supported in part by the UK Department of Science, Innovation and Technology, the Royal Academy of Engineering and multinational energy company Petronas.

The results were reported in Nature Chemical Engineering.

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