Researchers created a single-molecule catalyst that collects solar energy and converts it into hydrogen. (Image credit: Pixabay)
For the first time ever, scientists from Ohio State University have discovered a molecule that takes advantage of the visible spectrum of sunlight. The molecule can efficiently absorb sunlight and function as a catalyst to convert solar energy into hydrogen, which can be used as an alternative to fuel for vehicles that rely on gas to operate. Their findings were published in the journal Nature Chemistry on January 20th, 2020.
This new molecule can harness over 50% more solar energy than traditional solar cells can, which could result in the development of more efficient solar cells. The discovery will also help humans move away from fossil fuels and towards alternative, clean fuels, like hydrogen, that won’t contribute to climate change.
"The whole idea is that we can use photons from the sun and transform it into hydrogen. To put it simply, we are saving the energy from sunlight and storing it into chemical bonds so it can be used at a later time,” said Claudia Turro, a chemistry professor at Ohio State University.
Turro and her team discovered a particle that absorbs the sun’s low-energy infrared, a part of the spectrum that was difficult to collect in the past, which can quickly and efficiently convert it into hydrogen.
"What makes it work is that the system is able to put the molecule into an excited state, where it absorbs the photon and is able to store two electrons to make hydrogen," Turro said. "This storing of two electrons in a single molecule derived from two photons, and using them together to make hydrogen, is unprecedented."
Most attempts in the past to gather solar energy and transform it into hydrogen have focused on ultraviolet light. Many of these attempts relied on catalysts made of two or more molecules to transform solar energy into hydrogen. Using a catalyst made of one molecule to carry out the conversion process had failed, partly because the systems degraded quickly, and they didn’t collect energy from the full visible spectrum of sunlight.
Scientists were able to use a single rhodium molecule to absorb the entire visible light spectrum of the sun, from infrared to ultraviolet, which can also act as a catalyst to transform low-energy wavelengths into hydrogen without losing a significant amount of energy. This new system the team developed is nearly 25 times more efficient with low-energy near-infrared light than previous systems that used a single molecule.
During their experiments, researchers used LEDs to beam light onto acid solutions with the molecule suspended in them. When the light was beamed, the molecule produced hydrogen.
"I think the reason it works is because the molecule is difficult to oxidize," Turro said. "And we have to have renewable energy. Just imagine if we could use sunlight for our energy instead of coal or gas or oil, what we could do to address climate change."
Since it’s expensive to produce catalysts made of rhodium, scientists are looking to develop a system from less expensive materials. They will also be working to improve this single-molecule catalyst so it will produce hydrogen over a longer period of time.
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