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An American research team has developed a new technique to produce hydrogen from sunlight and water. It operates in an indoor environment and uses pure water, concentrated sunlight, and an indium gallium nitride photocatalyst.
Researchers at the University of Michigan have developed a new photocatalytic water splitting system that is reportedly capable of achieving a solar-to-hydrogen (STH) conversion efficiency of 9.2%.
The proposed system uses the higher energy part of the solar spectrum to split the water and the lower part of the spectrum to provide the heat that promotes the reaction. The extra heat also allows the hydrogen and oxygen to stay apart, instead of renewing their bonds and forming water once more.
It operates in an indoor environment and uses pure water, concentrated sunlight, and an indium gallium nitride photocatalyst. According to the scientists, the semiconductor catalyst, a forest of indium gallium nitride nanowires grown on a silicon surface, is capable of increasing its efficiency during use. The device absorbs photons and converts them into electrons, which are used to split water into hydrogen and oxygen.
The nanowires are studded with nanoscale metallic balls, 1/2000th of a millimeter in diameter, that use those electrons and holes—positively charged holes left behind when electrons are released by light—to help drive the reaction.
“A simple insulating layer over the panel keeps the temperature at a pleasant 75ºC (167 F), hot enough to support the reaction and cool enough for the semiconductor catalyst to work well,” the scientists explain.
They claim that the system is almost 10 times more efficient than other solar water separation systems of the same type. According to them, the final cost of hydrogen could decrease with a bigger semiconductor.
"We reduced the size of the semiconductor more than 100 times compared to some semiconductors that only work at low light intensity," said researcher Peng Zhou.
The research group describes the system in the study “ Solar-to-hydrogen efficiency of more than 9% in photocatalytic water splitting ”, published in Nature.
“This temperature-dependent strategy also leads to an STH efficiency of around 7% from widely available tap water and seawater and an STH efficiency of 6.2% in a large-scale water-splitting photocatalytic system. with a natural sunlight capacity of 257 watts,” they noted.
They said the next challenge is to further improve efficiency and generate ultra-high purity hydrogen that can directly power fuel cells. |
