Abstract
The low photocatalytic decomposition activity of TiO2 toward industrial pollutants at room temperature is one of the main obstacles for its practical application. TiO2-intercalated graphene oxide (GO) composites were prepared by in situ hydrolysis of butyl titanate in a GO aqueous solution, followed by hydrothermal reaction to improve their photoelectron separation efficiency. The in situ generated TiO2 nanocrystals could grow and adhere to the GO walls, thereby greatly improving the contact area and binding strength among them and resulting in low photoelectron transfer resistance. The photocatalytic activities of the as-prepared catalyst were evaluated via photodegradation of methylene blue (MB). The TiO2-intercalated GOs displayed much higher catalytic activity than GO, TiO2, and TiO2-adsorbed GOs. The degradation efficiency of MB by TiO2-intercalated GOs increased with increasing bath ratio of TiO2-intercalated GOs to MB solution, but it decreased with increasing initial concentration of MB. Degradation of MB by UV light was much faster than by simulated sunlight. The degradation time by sunlight was only 5% of degradation time by UV light. Cyclic catalytic experiments indicated that TiO2-intercalated GO maintained 99.97% degradation activity after repeated degradation (five times), thereby indicating the good decomposition durability.
Highlights
Solar energy has been used for 2.4 billion years
The redshifts into the visible regions demonstrated the significant influence of graphene oxide (GO) on the optical characteristics in which the adding of GOs narrowed the bandgap of TiO2 owing to the formation of Ti–O–C chemical bonding in their interface [39, 40]
3500–3800 cm−1 exhibited a wide range of absorption peaks, which can be attributed to the absorbed water by GOs [41]
Summary
Solar energy has been used for 2.4 billion years. Plants, including algae, can generate carbohydrate using water, carbon dioxide, and sunlight. TiO2-GR nanocomposites have been prepared via a facile hydrothermal reaction of graphene oxide (GO) and TiO2 in an ethanol-water solvent. Such TiO2-GR nanocomposites exhibited much higher photocatalytic activity and stability toward benzene gas, which is a volatile aromatic pollutant in air, than bare TiO2 [25]. GR is still limited because of the high contact resistance and low binding strength between prefabricated TiO2 nanocrystals due to their large morphology mismatch and lack of chemical interactions that lead to low contact area [29] To solve this problem, we synthesized closely integrated TiO2intercalated GO (TiO2-GO-TiO2 sandwich-like) composite nanosheets. The TiO2-GO-TiO2 nanosheets provide high photodecomposition efficiency and durability for the model dye, MB, compared with TiO2 and TiO2adsorbed GOs [30,31,32,33,34,35,36,37]
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