‘Wormlike’ hematite photoanode sets new world-record for solar hydrogen …

September 26, 2013 by  
Filed under Solar Energy Tips

According to the Ulsan National Institute of Science and Technology (UNIST), South Korea, researchers have developed a “wormlike” hematite photoanode capable of converting sunlight and water into clean hydrogen energy with an efficiency of 5.3 percent.  Details of the record-breaking achievement were published in Scientific Reports, in an article entitled “Single-crystalline, wormlike hematite photoanodes for efficient solar water splitting” on September 17.

A renewable and sustainable energy production method, solar water splitting uses sunlight, and water, the most abundant natural resource on earth.  Presently, low solar-to-hydrogen conversion efficiency plagues the commercialization of this technology.

The lynchpin in solar water splitting technology is the semiconductor photocatalysts that absorb solar energy and split water into hydrogen and oxygen.  Hematite, the rust of iron, Fe2O3, absorbs an abundance of sunlight.  In addition, it exhibits exceptional stability in water, low cost, and environmentally benign characteristics.  For these reasons, hematite has emerged as a promising candidate of photoanode material for solar water splitting within the last 20 years.  However, hematite has a perilous drawback of exceedingly poor electrical conductivity.  Thus, the majority of hematite anodes have performed poorly.

Professor Jae Sung Lee of UNIST led the joint research with Professor Kazunari Domen’s group at the  University of Tokyo, Japan, to develop a new anode material that has exceptional hydrogen production efficiency.

Lee and his colleagues made a series of modifications to improve the electrical conductivity of hematite: first, a single-crystalline wormlike creation was produced through a nanomaterial synthesis procedure; second, the researchers placed a small quantity of platinum into the hematite lattice as doping; lastly, a cobalt catalyst was used to drive the oxygen evolution reaction.  By making these modifications, the researchers drastically reduced energy loss and achieved the record-breaking solar-to-hydrogen conversion efficiency.

“The efficiency of 10 percent is needed for practical application of solar water splitting technology.  There is still [a] long way to reach that level.  Yet, our work has made an important milestone by exceeding [the] five percent level, which has been a psychological barrier in this field,” said Professor Lee.  “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 percent solar-to-hydrogen efficiency in [the] near future.”

The fellow researchers include Jae Young Kim from UNIST, and researchers from POSTECH and the University of Tokyo.  The research project received funding from the A3 Foresight Program of the Korean National Research Foundation, which supports international collaboration projects between Korea, China, and Japan.

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