Sunlight turns plastic waste into key element of hydrogen fuel cells
Our plastic waste problem is a large one, and it’s only getting larger. This is a huge environmental problem that requires some big picture thinking, but scientists are also exploring more subtle ways of chipping away at it and that includes turning plastic waste into sources of fuel. New research out of Singapore’s Nanyang Technological University (NTU) has thrown another interesting possibility into the mix, with scientists converting consumer plastic into a chemical used to to produce electricity in hydrogen fuel cells by exposing it to sunlight.
The key to the breakthrough was the introduction of a new kind of photocatalyst, which is a material that harnesses light energy to power chemical reactions. In search of new ways to convert plastic waste into useful chemicals, the NTU team turned to a type of affordable, biocompatible metal called vanadium. This commonly forms part of the steel and aluminum alloys used in cars and aircraft, but the scientists found it might play a role in plastics recycling, too.
By adding the vanadium-based catalyst to a solution containing consumer plastics, heating it to 85° C (185° F) and then exposing it all to artificial sunlight, the team was able to break down key bonds within the plastic in the space of six days. Breaking apart these carbon-carbon bonds typically involves high temperatures, which is energy-intensive, but by harnessing sunlight instead the scientists may have found a greener way forward.
But the eco-credentials of their technology don’t end there. The end result of this process was the conversion of the plastic into formic acid. This is a naturally occurring antibacterial agent and also happens to be the simplest combination of hydrogen and CO2 that we know of.
This makes it an exciting candidate as a carrier of liquid hydrogen in our pursuit of fuel cell vehicles. Last year, scientists in Switzerland built the world’s first fuel cell based on formic acid. The prototype device could produce 7,000 kWh of electricity every year with zero emissions, provided the formic acid comes from environmentally friendly sources, which could now include plastic trash.
“We aimed to develop sustainable and cost-effective methods to harness sunlight to manufacture fuels and other chemical products,” says research lead Assistant Professor Soo Han Sen. “This new chemical treatment is the first reported process that can completely break down a non-biodegradable plastic such as polyethylene using visible light and a catalyst that does not contain heavy metals.”
The team is continuing to tinker with its methods in hope of uncovering new kinds of chemicals that can be produced through broken down plastics, a possibility it says includes hydrogen gas.
The team published its research in the journal Science Advances.
Source: Nanyang Technological University