Bigger is not always better. Scientists as the University of California, San Diego are growing vast forests of very small “trees”–made of small branching wires–that collect sunlight, turning it into usable energy. This could mean a cheap way to deliver hydrogen fuel on a mass scale–lack of ability to do this is one reason hydrogen cars haven’t taken off.
It works through a process called photoelectrochemical water-splitting, analogous to the photosynthesis in plants, dividing molecules of water into component atoms: hydrogen and oxygen. The hydrogen gas can then be collected and used in everything from fuel cells to combustion engines.
Researchers have been keen to find cheap, stable, and non-toxic catalysts that make splitting water molecules more efficient, while simplifying the engineering. At the moment, the process is still expensive and energy intensive. While the San Diego team’s technology is not ready for commercialization, they have pushed ahead in creating a more efficient approach since their tree-like structures, complete with trunks and branches, have such enormous surface area. And the trees themselves are made from abundant natural materials, like silicon and zinc oxide.
Eventually, they hope to make the process even more like trees, so that the forests can covert solar energy directly into electricity. “We are trying to mimic what the plant does to convert sunlight to energy,” said Ke Sun, a PhD student in electrical engineering leading the project wrote on the UC San Diego Jacobs School of Engineering website. “We are hoping in the near future our ‘nanotree’ structure can eventually be part of an efficient device that functions like a real tree for photosynthesis.”MJC