A butterfly flaps its wings - and production of hydrogen could double. Scientists have developed pioneering technology that doubles hydrogen gas production after studying the structure of black butterfly wings.
Researchers studied two swallowtails, the Heng-chun birdwing (Troides aeacus) and the Red Helen (Papilio helenus Linnaeus) butterflies, the American Chemical Society's (ACS) National Meeting, in San Diego, USA, heard. Dr Tongxiang Fan and his team at China's Shanghai Jiao Tong University studied butterfly wings to discover ways to increase the amount of useful light gathered by solar collectors.
He says, "We realised that the solution to this problem may have been in existence for millions of years, fluttering right in front of our eyes, and that was correct. Black butterfly wings turned out to be a natural solar collector worth studying and mimicking."
Hydrogen, which is a renewable energy source, can be produced from water and sun. Developing technology can employ sunlight to increase the activity of catalysts that separate water into hydrogen and oxygen. The more powerful the solar collector, the better the technology works, says Dr Fan.
Nanostructures on butterfly wings make them extremely black and help researchers collect sunlight to make hydrogen gas from water; Credit: American Chemical Society
Butterfly wings include miniature scales that help butterflies collect sunlight so they can stay active in cold weather. Dr Fan's researchers studied the wings of black butterflies through an electron microscope to study the make-up of their scales. The black colour absorbs the highest levels of sunlight. Researchers first believed the secret was in the melanin pigment that caused the black colouring, but they recently began to investigate the role played by the scales.
The elongated scales are set in an overlapping pattern, like roof tiles. The pattern on the swallowtails differed a little, but each scale possessed ridges up the length along with tiny holes on each side that opened to a layer underneath.
The high walls channel sunlight into the holes and soak up longer wavelengths of light, at the same time they let shorter wavelengths filter through to the membrane underneath. The team confirmed this by using computer modelling.
The researchers copied the butterfly wing structures to produce solar collector templates. They used a dip-calcining process to change them to titanium dioxide, which they used as a catalyst to separate the water molecules.
The titanium dioxide scales were joined with platinum nanoparticles to boost their capability to split water. The result was that twice as much hydrogen gas was produced from water.
Dr Fan says the results show the potential of copying nature is creating renewable energy technology.
The study was financed by the National Natural Science Foundation of China and the Shanghai Rising-star Program.