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Nanotrees Turn Sunshine into Hydrogen Fuel

University of California, San Diego electrical engineers are building a forest of tiny nanowire trees in order to cleanly capture solar energy and harvest it for hydrogen fuel generation. Nanowires, which are made from abundant natural materials like silicon and zinc oxide, offer a cheap way to deliver hydrogen fuel on a mass scale.

“This is a clean way to generate clean fuel,” said Deli Wang, professor in the Department of Electrical and Computer Engineering at the UC San Diego Jacobs School of Engineering.

The trees’ vertical structure and branches are keys to capturing the maximum amount of solar energy, according to Wang, because the vertical structure of trees grabs and adsorbs light while flat surfaces simply reflect it. In images of Earth from space, light reflects off of flat surfaces such as the ocean or deserts, while forests appear darker.

Wang’s team has mimicked this structure in their 3D branched nanowire array, which uses a process called photoelectrochemical water-splitting to produce hydrogen gas. Water-splitting refers to the process of separating water into oxygen and hydrogen in order to extract hydrogen gas to be used as fuel. This process uses clean energy with no greenhouse gas byproduct. By comparison, the current conventional way of producing hydrogen relies on electricity from fossil fuels.

(UC San Diego)