Rust-based solar panels could make hydrogen cheap and efficient
- From: "Pluto" <pluto7@xxxxxxxxxx>
- Date: Tue, 19 Dec 2006 08:46:25 +0800
Solar-Powered Hydrogen Generation
Rust-based solar panels could make hydrogen cheap and efficient.
Researchers in Switzerland have demonstrated more-efficient water-splitting solar cells
based on a cheap, abundant, and long-lasting material: rust. The advance could lead to a
cheap and energy-efficient way to generate hydrogen for fuel-cell vehicles using solar
energy.
Water-splitting solar panels would have important advantages over existing technologies
in terms of hydrogen production. Right now, the primary way to make hydrogen is to
separate it from natural gas, a process that generates carbon dioxide and undercuts the
main motivation for moving to hydrogen fuel-cell vehicles: ending dependence on fossil
fuels. The current alternative is electrolysis, which uses electricity to break water
into hydrogen and oxygen, with the two gases forming at opposite electrodes. Although
electrolysis is costly, it can be cleaner if the source of the electricity is wind, sun,
or some other carbon-free source.
But if the source of the electricity is the sun, it would be much more efficient to use
solar energy to produce hydrogen by a photochemical process inside the cell itself. By
improving the efficiency of such solar panels, Michael Grätzel, chemistry professor at
the Ecole Polytechnique Fédérale de Lausanne, in Switzerland, and his colleagues have
taken an important step toward this goal.
The researchers have shown that by including small amounts of silicon and cobalt, they
can grow nanostructured thin films of iron oxide that convert sunlight into the
electrons needed to form hydrogen from water. And the iron oxide films do this more
efficiently than ever before with this material.
Iron oxide has long been an appealing material for such solar panels, in part because it
holds up well in contact with water. But although it can absorb sunlight, the resulting
charge carriers could not easily escape the material, so they recombined, canceling each
other out before they could split any water.
By doping the rust with silicon, the researchers coaxed the material to form
cauliflower-like structures with extremely high surface area, ensuring that a large part
of the atoms in the material were in contact with the water, or very close to it. That
way, holes could easily escape into the water, where they prompt the generation of
oxygen gas. The silicon also improves electron conductivity in the material, which is
important for generating hydrogen gas at an opposite electrode. The researchers further
improved the process by adding cobalt, which acts as a catalyst for the reactions.
http://www.technologyreview.com/read_article.aspx?id=17887&ch=energy
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