Improving Performance of Solar Nanotubes
Akira Fujishima, thirty-five years ago, discovered the electrochemical properties of titanium dioxide. He showed that titanium dioxide functioned as a photocatalyst. It produced hydrogen gas from water, electricity and sunlight. Scientists are quite hopeful regarding the qualities of Titania (or titanium dioxide). This is also known as white pigment. It’s used in many products be it paint, toothpastes or sunscreen lotions. Researchers have been exploring different ways to optimize the process started by Akira Fujishima. They want to develop a commercially viable technology that transforms cheap sunlight into hydrogen, a pollution-free fuel that can be stored and shipped.
A research team from Northeastern University and the National Institute of Standards and Technology (NIST) has found a way to improve the performance of nanotubes. They have discovered that a residue of a process used to build arrays of titania nanotubes is crucial in improving the performance of the nanotubes. Nanotubes are used in solar cells that produce hydrogen gas from water. They have reached to the conclusion that by controlling the deposition of potassium on the surface of the nanotubes, significant energy savings is possible.
If you want to derive maximum from a catalyst, you have to increase the available surface area. The team at Northeastern has been attempting to achieve exactly that. They are trying to devise a way to build tightly packed arrays of titania nanotubes. Titania nanotubes are known for a very high surface to volume ratio. Northeastern team is also developing means to incorporate carbon into the nanotubes. What will that achieve? Actually carbon helps titania absorb light in the visible spectrum. (Pure titania absorbs in the ultraviolet region, and much of the ultraviolet is filtered by the atmosphere.)
The research team felt the need to use the facilities available at the National Synchrotron Light Source (NSLS). NSLS is part of the Department of Energy’s Brookhaven National Laboratory. The NIST facility utilizes the X-rays that can be precisely adjusted to compute chemical bonds of specific elements. Using NIST X-ray spectroscopy beamline can provide result that is at least 10 times more sensitive than commonly available laboratory instruments. Researchers can identify elements at extremely low concentrations too.
The whole exercise didn’t prove very fruitful for the clean and green energy fraternity. But the whole process generated more interest when researchers compared the performance of the potassium-bearing nanotubes to similar arrays deliberately prepared without potassium. The potassium-bearing nanotubes needed only about one-third the electrical energy to produce the same amount of hydrogen as an equal array of potassium-free nanotubes. Latika Menon, who is the Northeastern physicist, shares her enthusiasm, “The result was so exciting, that we got sidetracked from the carbon research.” Why? Because potassium-bearing nanotubes has such a strong effect at nearly untraceable concentrations. Potassium might have played an unrecognized role in many experimental water-splitting cells that use titania nanotubes. It is to be noted that potassium hydroxide is commonly used in the cells. By manipulating potassium hydroxide hydrogen solar cell designers could use it to optimize performance.
