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Heterogeneous photocatalysis involves the use of a semi-conducting material which can be excited by the absorption of light. The most commonly employed photocatalyst material for research and industrial applications is titanium dioxide (TiO2). This is because it is photostable, chemically stable, photoactive, relatively inexpensive and non-toxic. Previous investigations performed in collaboration with researchers of the Lithuanian Energy Institute and Kaunas University of Technology researchers have shown that titanium films immersed into water vapor plasma are oxidized, surface is highly hydroxylated and chemically reactive. Research performed during 2012 revealed the evidence of the photocatalytic water splitting on the surface plasma oxidized titanium films under plasma radiation. We fabricated the hydrogenated nanocrystalline TiO2 thin films on the basis of a conceptually different approach. Titanium 0.2 - 0.7 μm thick films were sputterdeposited on silicon substrates and then treated in low-pressure (5 - 10 Pa) water vapor plasma at room temperature under continuous injection of water cloud vapor into vacuum chamber from the heated water container. The changes of microstructure, phase composition, elemental composition and surface morphology were investigated in dependence on the water vapor pressure, power dissipated in plasma and treatment duration. The following water splitting mechanism is suggested. When the surface of the oxidized titanium is in contact with the... [to full text]

Klasteris „Darni hibridinė energija“ vienija VDU Fizikos bei Matematikos ir statistikos katedrų dėstytojus, doktorantus ir studentus bei Lietuvos energetikos instituto (LEI) tyrėjus. Pagrindinis klasterio tikslas – sukurti naujas fundamentinių ir taikomųjų mokslo žinias, kurios sudarytų mokslines prielaidas žaliajai energijai skverbtis į Lietuvos pramonę, didintų energetinį jos saugumą ir patikimumą vietinių ir atsinaujinančių energijos išteklių platesnio panaudojimo sąskaita ir mažintų socialines įtampas. Pateikti eksperimentiniai tyrimai atlikti LEI vandenilio technologijų tyrimų centre. Titanium oxide is an important material in both the energy and environmental applications, ranging from photovoltaics and photocatalysis to photo/electrochromics and sensors. Recently [S. S. Mao, X. Chen, L. Liu and P. Y. Yu, Science 331 (2011) 746], it has been shown that titanium oxide modified with hydrogen demonstrates properties attractive for photocatalytic under visible light applications. To enhance solar absorption we fabricated the double-layered hydrogenated-TiO2/Ti nanocrystalline thin films on the basis of a conceptually different approach performing oxidation of Ti thin films in water vapor plasma under continuous highflux, low energy ion irradiation at room temperature [L. L. Pranevicius, D. Milcius, S. Tuckute, K. Gedvilas, Preparation of hydrogenated-TiO2/Ti double layered thin films by water vapor plasma treatment, Appl. Surf. Sci. (2012), http://dx.doi.org/10.1016/j.apsusc.2012.05.061]. It is demonstrated that the near-surface region of plasma treated Ti film is converted into the hydrogenated nanocrystalline TiO2.