Solar energy has a number of benefits over "dirty" fossil fuels but the problem is it can only be harvested during the day; researchers may have found a solution.
A research team created a device that can convert the Sun's rays into hydrogen fuel (as opposed to electricity) which can be stored for later use, a University of North Carolina at Chapel Hill news release reported.
"So called 'solar fuels' like hydrogen offer a solution to how to store energy for nighttime use by taking a cue from natural photosynthesis," Tom Meyer, Arey Distinguished Professor of Chemistry at UNC's College of Arts and Sciences, said. "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 Sun holds enough power to fuel every "vehicle, factory and device on the planet "for a year in only an hour's time; this energy can be captured using solar panels. The downside is that when the Sun goes down, that power disappears with it.
The new system aims to hold onto the Sun's immense power even during the dark hours of night. The method uses a dye-sensitized photoelectrosynthesis cell (DSPEC) uses solar energy to create hydrogen fuel; it does this by splitting "water into its component parts." Once the water is split the hydrogen is stored while the oxygen is released back into the atmosphere.
"But splitting water is extremely difficult to do," Meyer said. "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."
This specific design employs a molecule and a nanoparticle. The molecule (called a "chromophore-catalyst assembly") works to absorb the sunlight and then cues the catalyst to begin separating the electrons from the water.
"The nanoparticle, to which thousands of chromophore-catalyst assemblies are tethered, is part of a film of nanoparticles that shuttles the electrons away to make the hydrogen fuel," the news release reported.
The system kept crashing because either the chromophore-catalyst would break away from the nanoparticles or electrons were not ripped away fast enough to produce hydrogen.
To solve this issue the researchers looked to a technique that coated each nanoparticle with a thin layer of titanium dioxide. This resulted in the atoms carrying electrons away at a much higher speed. They also created a protective coating that kept the chromophore-catalyst assemblies from escaping their tethers.
The new system allows researchers to effectively generate fuel without releasing harmful greenhouse gases into the atmosphere.
"When you talk about powering a planet with energy stored in batteries, it's just not practical," Meyer said. "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."
