by Gage Taylor
Inspired by the way plants convert sunlight into energy, scientists at the Ulsan National Institute of Science and Technology in South Korea have developed a new type of photoelectrode that boosts the ability of solar water-splitting to produce hydrogen, an essential process in the development of hydrogen as a fuel source. The special photoelectrode is capable of absorbing a high percentage of visible light from the sun and then using it to split water molecules into hydrogen and oxygen. The multilayered photoelectrode has a two-dimensional hybrid metal-dielectric structure that consists of three layers: gold film, ultrathin TiO2 (titanium dioxide), and gold nanoparticles. According to the team’s study published last month in Nano Energy, this structure shows high light absorption, which in turn significantly enhances its photocatalytic applications.
In contrast to preexisting designs, according to Professor Jeong Min Baik, one of the project’s leaders, “this is the first time to use the metal-dielectric hybrid-structured film with TiO2 for oxygen production.” This particular structure incorporates plasmonic metal nanoparticles (i.e. the gold nanoparticles) to enhance photoactivity in almost the entire visible region of the solar spectrum (95% according to their report, which is in turn about 40% of full sunlight). Plasmonic nanoparticles are particles whose electron density can couple with electromagnetic radiation of wavelengths that are far larger than the particle, unlike a pure metal where there is a maximum limit on what size wavelength can be effectively coupled.
Prof. Heon Lee, another of the project’s leaders, wrote, “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.” If this team of researchers is correct, mass production of hydrogen could soon be both possible and affordable. Given that much of the interest in hydrogen power has come from locations with underdeveloped energy infrastructure, such as South Africa, this could be a big step forward in making hydrogen a viable fuel source.
Joonmo Park, Hee jun Kim, SangHyeon Nam, Hyowook Kim, Hak-Jong Choi, Youn Jeong Jang, Jae Sung Lee*, Jonghwa Shin*, Heon Lee*, and Jeong Min Baik. “Two-dimensional metal-dielectric hybrid-structured film with titanium oxide for enhanced visible light absorption and photo-catalytic application.” Nano Energy. 2016.
Ulsan National Institute of Science and Technology. “New technique for turning sunlight into hydrogen.” [http://www.eurekalert.org/pub_releases/2016-02/unio-ntf021416.php]