Wormlike hematite photoanode breaks world-record for solar hydrogen production efficiency

Schematic diagram of PEC cell with hematite thin-film photoanode
Schematic diagram of PEC cell with hematite thin-film photoanode

The science journal Scientific Reports on September 17th, 2013, released the results of the research “Single-crystalline, wormlike hematite photoanodes for efficient solar water splitting”. Researchers at the Ulsan National Institute of Science and Technology (UNIST) (Ulsan, South Korea), developed a “wormlike” hematite photoanode converting sunlight and water to clean hydrogen energy with an efficiency of 5.3%.

Financed by the A3 Foresight Program of the Korean National Research Foundation which supports international collaboration projects between Korea, China and Japan, UNIST broke the previous record of solar hydrogen efficiency among stable oxide semiconductor photoanodes, which was 4.2% and owned by the research group of Prof. Michael Graetzel at the Ecole Polytechnique de Lausanne (EPFL), Switzerland.


Hematite absorbs an ample amount of sunlight

Solar water splitting is a renewable energy production method utilizing sunlight and water at the same time. Key to this technology are semiconductor photocatalysts that absorb sunlight and split water to hydrogen and oxygen using the absorbed solar energy. Hematite, an iron oxide (Fe2O3) absorbs an ample amount of sunlight. It also provides excellent stability in water, allowas for a low price, and offers environmentally-friendly characteristics.

Although it has been a most popular and promising candidate of photoanode material for solar water splitting over the last two decades, hematite has a critical drawback of an extremely poor electrical conducting property, and most of the hematite anodes have exhibited very low performance. Nowadays low solar-to-hydrogen conversion efficiency is still the most serious hurdle to overcome in the commercialization of this technology.


Promising results at UNIST

Prof. Jae Sung Lee of UNIST and Prof. Kazunari Domen’s group at the University of Tokyo, Japan, developed a new anode material with outstanding hydrogen production efficiency employing a series of modifications to improve the property of hematite reducing energy loss due to charge recombination and bringing the record-breaking solar-to-hydrogen conversion efficiency.

First, a unique single-crystalline “wormlike” morphology was produced by using a nanomaterial synthesis technique. Second, a small amount of platinum was introduced into the hematite lattice as doping. Finally, a cobalt catalyst was employed to help oxygen evolution reaction.

“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,” stated Prof. Jae Sung 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% solar-to-hydrogen efficiency in a near future.”


2013-09-27 | Courtesy: UNIST | solarserver.com © Heindl Server GmbH

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