Researchers at UNC-Chapel Hill say they have found a way to turn solar power into a 24-hour-a-day power source by using the sun’s energy to separate water molecules and create hydrogen fuel.

In making the breakthrough, they received a powerful boost from scientists at N.C. State.

UNC disclosed the potential breakthrough for a clean energy source on Tuesday. Researchers in Chapel Hill have been seeking to develop so-called “solar fuels” based on the conversion of the sun’s power through an ”artificial photosynthesis” since the program began in 2009 with federal funding support.

“So called ‘solar fuels’ like hydrogen offer a solution to how to store energy for nighttime use by taking a cue from natural photosynthesis,” said Tom Meyer, who is Arey Distinguished Professor of Chemistry at UNC’s College of Arts and Sciences. “Our new findings may provide a last major piece of a puzzle for a new way to store the sun’s energy – it could be a tipping point for a solar energy future.”

The research into a new process called dye-sensitized photoelectrosynthesis cell, or DSPEC, took place at UNC’s Energy Frontier Research Center. Scientists were looking for a way to harvest benefits of clean solar power long after the sun went down.

“When you talk about powering a planet with energy stored in batteries, it’s just not practical,” said Meyer. “It turns out that the most energy dense way to store energy is in the chemical bonds of molecules. And that’s what we did – we found an answer through chemistry.”

DSPEC splits water into hydrogen and oxygen with the hydrogen being stored. Sophisticated nanotechnology is involved, and DSPEC research has been conducted for several years, according to UNC.

Meyer’s work involves a molecule and a nanoparticle. The molecule, which is called a chromophore-catalyst assembly, absorbs sunlight and then “kick starts” the catalyst to rip electrons away from water, UNC explained. Thousands of those molecules are tethered to nanoparticles, and as the particles split from the oxygen the electrons needed for the hydrogen are carried away. According to Meyer, the electrons couldn’t be transported away fast enough to create the hydrogen.

“But splitting water is extremely difficult to do,” Meyer explained. “You need to take four electrons away from two water molecules, transfer them somewhere else, and make hydrogen, and, once you have done that, keep the hydrogen and oxygen separated. How to design molecules capable of doing that is a really big challenge that we’ve begun to overcome.”

That’s where the NCSU effort came in.

Greg Parsons, Alcoa Professor in the Department of Chemical and Biomolecular Engineering and also Director of NCSU’s Nanotechnology Initiative, and his team developed a process to coat the nanoparticles with group to use a technique that coated the nanoparticle with titanium dioxide. The coating enabled a faster process as well as a means of keeping the molecules tethered safely, according to UNC.

Almost no external energy is needed, according to Meyer.

And more clean energy news may be coming.

The same process also might be used to reduce carbon dioxide in other fuels.