New way to turn sunlight into hydrogen developed

Inspired by the way plants convert sunlight into energy, Korean scientists have developed a new type of multi-layered photoelectrode that boosts the ability of solar water-splitting to produce hydrogen.
The special photoelectrode (Au NPs/TiO2/Au) is capable of absorbing visible light from the Sun and then using it to split water molecules (H2O) into hydrogen and oxygen.
It takes the form of two-dimensional hybrid metal-dielectric structure, which mainly consists of three layers of gold (Au) film, ultra-thin TiO2 layer, and gold nanoparticles (Au NPs).
A team of researchers affiliated with Ulsan National Institute of Science and Technology (UNIST) in South Korea reported that this promising photoelectrode shows high light absorption of about 90 per cent in the visible range 380-700 nanometre (nm), as well as significant enhancement in photo-catalytic applications.

Many structural designs, such as hierarchical and branched assemblies of nanoscale materials have been suggested to increase the ultraviolet (UV)-visible absorption and to enhance water-splitting efficiency.
However, through incorporation of plasmonic metal nanoparticles (Au) to TiO2 structures, their photoelectrodes have shown to enhance the photoactivity in the entire UV-visible region of solar spectrum when compared with the existing ones, the team said.

"Several attempts have been made to use UV-based photoelectrodes for hydrogen production, but this is the first time to use the metal-dielectric hybrid-structured film with TiO2 for oxygen production," said Professor Jeong Min Baik of UNIST.
Moreover, according to Baik, this special type of photoelectrode uses approximately 95 per cent of the visible spectrum of sunlight, which makes up a substantial portion (40 per cent) of full sunlight.

"The developed technology is expected to improve hydrogen production efficiency," he added.
"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," said Professor Heon Lee from Korea University.
"Using nanoimprint lithography, mass production of hydrogen will be soon possible," said Baik.
"This simple system may serve as an efficient platform for solar energy conversion, utilising the whole UV-visible range of solar spectrum based on two-dimensional plasmonic photoelectrodes," he added.
The study was published in the journal Nano Energy.