Solar cell directly splits water for hydrogen

[OKIsItJustMe]

http://www.eurekalert.org/pub_releases/2008-02/ps-scd021108.php

< Back to EurekAlert! >Public release date: 17-Feb-2008
Contact: Andrea Elyse Messer
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Penn State

Solar cell directly splits water for hydrogen

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"This is a proof-of-concept system that is very inefficient. But ultimately, catalytic systems with 10 to 15 percent solar conversion efficiency might be achievable," says Thomas E. Mallouk, the DuPont Professor of Materials Chemistry and Physics. "If this could be realized, water photolysis would provide a clean source of hydrogen fuel from water and sunlight."

Although solar cells can now produce electricity from visible light at efficiencies of greater than 10 percent, solar hydrogen cells—like those developed by Craig Grimes, professor of electrical engineering at Penn State—have been limited by the poor spectral response of the semiconductors used. In principle, molecular light absorbers can use more of the visible spectrum in a process that is mimetic of natural photosynthesis. Photosynthesis uses chlorophyll and other dye molecules to absorb visible light.

So far, experiments with natural and synthetic dye molecules have produced either hydrogen or oxygen-using chemicals consumed in the process, but have not yet created an ongoing, continuous process. Those processes also generally would cost more than splitting water with electricity. One reason for the difficulty is that once produced, hydrogen and oxygen easily recombine. The catalysts that have been used to study the oxygen and hydrogen half-reactions are also good catalysts for the recombination reaction.

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The water splitting requires 1.23 volts, and the current experimental configuration cannot quite achieve that level so the researchers add about 0.3 volts from an outside source. Their current system achieves an efficiency of about 0.3 percent.

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http://live.psu.edu/story/28853

[sam sarrha]

1. solar panels have been developed that turn Infra red into electricity, much more efficiently than

light, and work when it is cloudy, they even work at night, it can be made in plastic rolls