Gold Layers Boost Water Splitting Efficiency

By sandwiching an ultrathin layer of titanium dioxide between gold, researchers have boosted the light absorption range of water splitting catalysts.

AsianScientist (Feb. 29, 2016) – A team of researchers from South Korea has developed a new type of multilayered photoelectrode that can absorb 95 percent of the light in the visible range (390-700nm) for the production of hydrogen from water. Their results, which demonstrate a significant enhancement in efficiency, have been published in Nano Energy.

Thanks to its chemical stability and low cost, titanium dioxide (TiO2) is widely used in the laboratory as a catalyst to split water and obtain hydrogen. However, TiO2-based catalysts have not been commercially successful due to a number of limitations, including their narrow absorption range and slow reaction kinetics.

To increase the absorption range and enhance water-splitting efficiency, many structural designs such as hierarchical and branched assemblies of nanoscale materials have been proposed. In the present study, a team led by Professor Baik Jeong Min from the Ulsan National Institute of Science and Technology have used gold to increase the absorption of TiO2 thin films to 95 percent of the visible spectrum.

As the visible spectrum makes up a substantial portion (40 percent) of full sunlight, Baik expects that their multilayered photoelectrode will improve the efficiency of hydrogen production.

“Several attempts have been made to use UV-based photoelectrodes for hydrogen production, but this is the first time a metal-dielectric hybrid-structured film with TiO2 has been used for oxygen production,” Baik explained.

The photoelectrode takes the form of two-dimensional hybrid metal-dielectric structure consisting of three layers: gold film, an ultrathin TiO2 layer (20 nm), and gold nanoparticles.

(a) Schematic, (b) scanning electron micrograph and (c) absorption spectra of the two-dimensional metastructured film with TiO2 (black, red and blue). Credit: UNIST.
(a) Schematic, (b) scanning electron micrograph and (c) absorption spectra of the two-dimensional metastructured film with TiO2 (black, red and blue). Credit: UNIST.

“This metal-dielectric hybrid-structured film is expected to further reduce the overall cost of producing hydrogen, as it doesn’t require complex operation processes. Using nanoimprint lithography, mass production of hydrogen will be soon possible,” said Professor Lee Heon of Korea University, the co-corresponding author of the study.

“This simple system may serve as an efficient platform for solar energy conversion, utilizing the whole UV-visible range of solar spectrum based on two-dimensional plasmonic photoelectrodes,” Baik added.

The article can be found at: Park et al. (2016) Two-Dimensional Metal-Dielectric Hybrid-Structured Film with Titanium Oxide for Enhanced Visible Light Absorption and Photo-Catalytic Application.


Source: UNIST; Photo: Shutterstock.
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