Clean Power

Published on September 27th, 2013 | by James Ayre


Solar Hydrogen Production Efficiency World Record Broken — “Wormlike” Hematite Photoanode Crushes Old Record

September 27th, 2013 by  

A new world record has been set for solar hydrogen production efficiency — the new record-breaking efficiency of 5.3% blows past the previous record of 4.2%, thanks in large part to the development of a new “wormlike” hematite photoanode. The new photoanode was developed by researchers from the Ulsan National Institute of Science and Technology (UNIST) in South Korea, and from the University of Tokyo in Japan.

The impressive jump from a record efficiency of 4.2% to 5.3% was achieved by the researchers through the utilization of an entirely new method/different materials — whereas the previous record was set by researchers (from the Ecole Polytechnique de Lausanne in Switzerland) using stable oxide semiconductor photoanodes, the new record was set via the use of the new worm-like hematite photoanode.

Schematic Diagram of PEC cell with wormlike hematite photoanode. Image Credit: Copyright UNIST

Schematic Diagram of PEC cell with wormlike hematite photoanode.
Image Credit: Copyright UNIST

Regular, everyday hematite (iron rust, Fe2O3) is a very effective semiconductor photocatalyst with regard to solar water splitting technology — thanks to its ability to absorb an ample amount of sunlight, its great stability in water, great availability/low price, and its environmentally benign characteristics — but it has a major flaw, possessing extremely poor electrical conductivity. This flaw has limited the potential performance of solar water-splitting technologies, but, now, the new modified form of hematite which the researchers have created addresses this limitation.

The press release from UNIST explains:

The researchers employed a series of modifications to improve the property of hematite. 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. These modifications reduced energy loss due to charge recombination and brought the record-breaking solar-to-hydrogen conversion efficiency.

“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 lead researcher Jae Sung Lee of UNIST. “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.”

The new research was just published in the journal Scientific Reports.

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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.

  • spottedmankee

    This article is misleading. In this study, they studied photoanodes which had good photocurrents but not until rather positive potentials. Therefore, the “solar hydrogen production efficiency” is ZERO. It’s hard to explain it in a comment section, but it is the responsibility of the researchers and journalists to avoid misleading and false statements like this (in fact, they do not claim “efficiency” in the paper, just in this article summary).

  • NRG4All

    It seems to me that no matter what the conversion efficiency, you still have the problems of storage, economical transportation, and refueling infrastructure to name a few. This fuel only lends itself to centralized distribution (i.e. existing oil company filling stations), whereas pure EV can be refueled nearly anywhere. I just visited a Tesla showroom and was told that Tesla is working on a 400 mile battery that is a combination of Li-Ion for short trips with a Zinc-Air battery to supplement long trips. I don’t plan on driving more than 400 miles per day on a trip so even ubiquitous L2 charging could suffice at motels. Hopefully the best system will win out in the end without undue interference.

  • Matt

    I see they produce 25% higher than the old record. But it isn’t clear to me what the “efficiency of 5.3%” is based on. I thought this was a solar splitter, so they aren’t inputing electric; are they?

    • Pramod

      Efficiency is related to Solar To HYdrogen STH Conversion – It is surely very high value

  • Marion Meads

    They need to achieve minimum of 10% solar energy to H2 energy to become commercially viable. They should keep trying.

    • JamesWimberley

      What´s the economic basis for this limit, even if it looks plausible? I assume the efficiency is in relation to the electrical input, which is ex hypothesi renewable. But this input is getting cheaper all the time, especially as down the road we are looking at surplus energy that has zero immediate use value.

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