Nanoporous hydrogenated TiO2 photocatalysts generated by underwater discharge plasma treatment for solar photocatalytic applications

In this paper, we report on the mass production, characteristics and application of a hydrogenated TiO2 photocatalyst (H-TiO2) with high reactivity under solar light irradiation. The H-TiO2 photocatalyst has been prepared by simple sol-gel method/underwater discharge plasma treatment at room temperature and atmospheric pressure. The optical absorption spectrum of TiO2 can be extended from the ultraviolet (UV) into the visible range by changing the surface properties. The crystallinity, hydrogenation and porosity of TiO2 can be greatly enhanced within 90 s through underwater discharge plasma, using amorphous TiO2 (as-synthesized TiO2, alpha-TiO2) as the precursor. The resultant H-TiO2 showed high bicrystalline (anatase/brookite phases) and a large surface area (267.5 m(2)/g), thus improving photocatalytic activity. We have demonstrated that H-TiO2 showed significant photocatalytic efficiencies for degradation of reactive black 5, rhodamine B, and phenol under solar light irradiation, up to 10 times higher than those of commercial TiO2 and alpha-TiO2, leading to complete water purification. Interestingly, the H-TiO2 photocatalyst also exhibited strong antimicrobial activities against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus under solar light irradiation, up to 5-times greater than those of commercial TiO2 and alpha-TiO2. Given that H-TiO2 can be mass produced and easily processed by underwater discharge plasma, we expect this plasma technology may find important environmental and medical applications. (C) 2017 Elsevier B.V. All rights reserved.