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.
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.