Turning waste plastic into clean hydrogen and valuable graphene

Researchers from Rice University have unveiled a revolutionary method to harness hydrogen from plastic waste, offering an eco-friendly and cost-effective alternative to traditional hydrogen production. This innovative approach not only addresses environmental concerns but also has the potential to be economically lucrative.

Hydrogen is increasingly regarded as a promising substitute for fossil fuels, but current production methods are plagued by excessive carbon dioxide emissions and high costs. However, Rice University scientists have discovered a way to extract hydrogen from various types of plastic waste, including unsorted and unwashed plastics, using a low-emission technique that could potentially cover its own expenses.

Kevin Wyss, a lead author of the study and a Rice doctoral alumnus, explains, “In this work, we converted waste plastics into high-yield hydrogen gas and high-value graphene. If the produced graphene is sold at only 5% of the current market value – a 95% discount – clean hydrogen could be produced essentially for free.”

To put this into perspective, traditional ‘green’ hydrogen, produced through renewable energy methods, costs around $5 for just over two pounds. Nevertheless, the majority of the nearly 100 million tons of hydrogen consumed globally in 2022 was derived from fossil fuels, contributing roughly 12 tons of carbon dioxide emissions per ton of hydrogen.

James Tour, a professor of Chemistry and Materials Science and Nanoengineering at Rice University, emphasizes the urgency of rethinking hydrogen production methods: “The main form of hydrogen used today is ‘gray’ hydrogen, which is produced through steam-methane reforming, a method that generates a lot of carbon dioxide. With the demand for hydrogen expected to soar in the coming decades, maintaining the status quo is no longer an option if we are committed to achieving net-zero emissions by 2050.”

The researchers’ breakthrough involved exposing waste plastic samples to rapid flash Joule heating for approximately four seconds, elevating their temperature to a scorching 3100 degrees Kelvin. This process effectively vaporized the hydrogen contained within the plastics, leaving behind graphene – an incredibly lightweight and resilient material composed of a single layer of carbon atoms.

Kevin Wyss notes the early observations of the process: “When we first discovered flash Joule heating and applied it to upcycle waste plastic into graphene, we observed a lot of volatile gases being produced and shooting out of the reactor. We suspected a mix of small hydrocarbons and hydrogen but lacked the instrumentation to study their exact composition.”

Thanks to funding from the United States Army Corps of Engineers, the research team acquired the necessary equipment to analyze the vaporized contents. Wyss states, “We know that polyethylene, for example, is made of 86 percent carbon and 14 percent hydrogen, and we demonstrated that we are able to recover up to 68% of that atomic hydrogen as gas with a 94% purity.”

The significance of this achievement extends beyond hydrogen production. Wyss adds, “Developing the methods and expertise to characterize and quantify all the gases, including hydrogen, produced by this method was a difficult but rewarding process for me. I hope that this work will allow for the production of clean hydrogen from waste plastics, possibly solving major environmental problems like plastic pollution and the greenhouse gas-intensive production of hydrogen by steam methane reforming.”

This groundbreaking discovery not only promises a greener future for hydrogen production but also presents a potential solution to the global issue of plastic pollution. With further research and development, this innovative method could play a pivotal role in achieving a sustainable and carbon-neutral energy future.