To understand why this is important, we first have to understand what is solar water splitting. Solar water splitting is the process of splitting a molecule of water to release hydrogen which can be used for energy purposes. Solar water splitting can be considered as a completely renewable and sustainable energy production process--because it uses sunlight as the main source of energy.
The success of this technology hinges on the semiconductor photo-catalysts that absorbs sunlight. In this same manner--hematite, an iron oxide also absorbs sunlight. So these researchers found a way to develop a hematite photo-anode that absorbs this sunlight and splits water to clean hydrogen energy with a record-breaking high efficiency of 5.3% -- breaking the previous record of 4.2%. This hematite photo-anode is better because of its excellent stability in water, inexpensive nature, and is environmentally very friendly.
"The efficiency of 10% is needed for practical application of solar water splitting technology. There is still long way to reach that level. Yet, our work has made an important milestone by exceeding 5% level, which has been a psychological barrier in this field. It has also demonstrated that the carefully designed fabrication and modification strategies are effective to obtain highly efficient photocatalysts and hopefully could lead to our final goal of 10% solar-to-hydrogen efficiency in a near future." Prof. Jae Sung Lee of UNIST, lead of the joint research with Prof. Kazunari Domen's group at the University of Tokyo, Japan. (ref)
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