Hydrogen gas is a promising "green" fuel. The lightest chemical element, hydrogen is an efficient energy store and could potentially replace gasoline in vehicles. However, the element does not exist in large amounts in nature, and must be produced artificially.
Hydrogen can be produced by splitting water (H2O) into hydrogen (H2) and oxygen (O2). There are many ways to do this, but among the cleanest -- hence most attractive -- is using solar cells. These devices capture the energy of sunlight to drive the water-splitting reaction.
Sunlight comes in a spectrum, with each color having a different wavelength. Solar cells must absorb light of particular wavelengths, depending on how much energy the cell needs to drive the reaction. The more of the spectrum it captures, the more hydrogen it produces. Unfortunately, most cells only absorb shorter wavelengths of light, corresponding to the higher energy region of visible light below the red light domain. This means that while colors such as blue and green light can be used, the rest is wasted.
Now, researchers at Kyushu University in Japan and its Institute for Carbon-Neutral Energy Research (I2CNER) have potentially solved this problem. They invented a device driven by near-infrared (NIR) light -- the part of the spectrum, invisible to the naked eye, with wavelengths longer than visible red light. Thus, they enabled a broader spectrum of light, including UV, visible, and NIR, to be harvested. Their design cleverly exploits the chemistry of ruthenium, a heavy metal related to iron. Their achievement was reported in Angewandte Chemie International Edition.
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