Abstract
We report an effect involving hydrogen (H2)-plasma-treated nanoporous TiO2(H-TiO2) photocatalysts that improve photocatalytic performance under solar-light illumination. H-TiO2 photocatalysts were prepared by application of hydrogen plasma of assynthesized TiO2(a-TiO2) without annealing process. Compared with the a-TiO2, the H-TiO2 exhibited high anatase/brookite bicrystallinity and a porous structure. Our study demonstrated that H2 plasma is a simple strategy to fabricate H-TiO2 covering a large surface area that offers many active sites for the extension of the adsorption spectra from ultraviolet (UV) to visible range. Notably, the H-TiO2 showed strong ·OH free-radical generation on the TiO2 surface under both UV- and visible-light irradiation with a large responsive surface area, which enhanced photocatalytic efficiency. Under solar-light irradiation, the optimized H-TiO2 120(H2-plasma treatment time: 120 min) photocatalysts showed unprecedentedly excellent removal capability for phenol (Ph), reactive black 5(RB 5), rhodamine B (Rho B) and methylene blue (MB) — approximately four-times higher than those of the other photocatalysts (a-TiO2 and P25) — resulting in complete purification of the water. Such well-purified water (>90%) can utilize culturing of cervical cancer cells (HeLa), breast cancer cells (MCF-7), and keratinocyte cells (HaCaT) while showing minimal cytotoxicity. Significantly, H-TiO2 photocatalysts can be mass-produced and easily processed at room temperature. We believe this novel method can find important environmental and biomedical applications.
Highlights
TiO2 modification by hydrogen has received attention[17,18,19,20]
hydrogenated nanoporous TiO2 (H-TiO2) nanoparticles were synthesized from the reaction of hexadecyltrimethylammonium bromide (CTAB) with titanium (IV) butoxide with no additional heat treatment
H-TiO2 synthesis entails the following steps: (i) surfactants (CTAB) are dissolved in distilled water to produce micelles acting as nanopore structures in the formation of TiO2; (ii) TiO2 precursor is added to the surfactant solution in a sol-gel process; (iii) this mixture is treated with H2 plasma to remove the micelles and to synthesize crystalline TiO2 photocatalysts
Summary
TiO2 modification by hydrogen has received attention[17,18,19,20]. Zheng et al reported that hydrogenated TiO2 expands the light-absorption spectra and enhances the separation of photoelectrons and holes[21]. There have been several reports related to hydrogenated TiO2 with porous structures to further improve photocatalytic efficiency of TiO226,27. We performed the fabrication of hydrogenated nanoporous TiO2 (H-TiO2) that covers a large surface area (427.5 m2/g) using a hydrogen (H2) plasma treatment system. The water purified by H-TiO2 was further evaluated in an in vitro cytotoxicity test which measures the level of water purification[28] and monitors by-products after the photocatalytic treatment. This preliminary study served to highlight the potential of mass-production of nanoporous photocatalysts with a high coverage of surface area for environmental and biomedical applications
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