Degradation of Harmful Organics Using Visible Light Driven N-TiO₂/rGO Nanocomposite

Simple synthesis of BiOI/ZnO/rGO for efficient photocatalytic degradation of antibiotic chloramphenicol under visible light

BiOI/ZnO/rGO (reduced graphene oxide) composite photocatalyst was fabricated using a simple one-step hydrothermal process and applied to the degradation of antibiotic chloramphenicol (CAP). By tuning the Bi/Zn ratios, the structure and photoelectric properties of the catalyst were investigated and characterized in terms of their morphological, structural, optical and photoelectrochemical properties. The as-synthesized composite photocatalysts are well-crystalline, uniform dispersion and exhibit good photocatalytic properties. The photocatalytic degradation rate of CAP by BiOI/ZnO/rGO composite is 8.1 times and 1.8 times that of BiOI and ZnO, respectively. The photocatalytic mechanism studies revealed that the synergistic effect between rGO and BiOI/ZnO can effectively separate photogenerated electron-hole, enhance photocurrents and conductivity, and improve charge carrier densities. Moreover, BiOI/ZnO/rGO possesses good stability and reusability that the degradation efficiency remained above 80% even after 5 recycling. This study reveals that both the introduction of rGO and heterostructure construction between BiOI and ZnO play a crucial role in their photoelectrochemical and photocatalytic properties.

Vertical Growth of WO3 Nanosheets on TiO2 Nanoribbons as 2D/1D Heterojunction Photocatalysts with Improved Photocatalytic Performance under Visible Light

We report the construction of 2D/1D heterojunction photocatalysts through the hydrothermal growth of WO3 nanosheets on TiO2 nanoribbons for the first time. Two-dimensional WO3 nanosheets were vertically arrayed on the surface of TiO2 nanoribbons, and the growth density could be simply controlled by adjusting the concentration of the precursors. The construction of WO3/TiO2 heterojunctions not only decreases the band gap energy of TiO2 from 3.12 to 2.30 eV and broadens the photoresponse range from the UV region to the visible light region but also significantly reduces electron–hole pair recombination and enhances photo-generated carrier separation. Consequently, WO3/TiO2 heterostructures exhibit improved photocatalytic activity compared to pure WO3 nanosheets and TiO2 nanoribbons upon visible light irradiation. WO3/TiO2-25 possesses the highest photocatalytic activity and can remove 92.8% of RhB pollutants in 120 min. Both further increase and decrease in the growth density of WO3 nanosheets result in an obvious reduction in photocatalytic activity. The kinetic studies confirmed that the photocatalytic degradation of RhB follows the kinetics of the pseudo-first-order model. The present study demonstrates that the prepared WO3/TiO2 2D/1D heterostructures are promising materials for photocatalytic removal of organic pollutants to produce clean water.

Immobilised rGO/TiO2 Nanocomposite for Multi-Cycle Removal of Methylene Blue Dye from an Aqueous Medium

This work presents the immobilisation of titanium dioxide (TiO2) nanoparticles (NPs) and reduced graphene oxide (rGO)-TiO2 nanocomposite on glass sheets for photocatalytic degradation of methylene blue (MB) under different radiation sources such as ultraviolet and simulated solar radiation. The TiO2 NPs and rGO-TiO2 nanocomposite were synthesised through a simple hydrothermal method of titanium isopropoxide precursor followed by calcination treatment. Deposition of prepared photocatalysts was performed by spin-coating method. Additionally, ethylene glycol was mixed with the prepared TiO2 NPs and rGO-TiO2 nanocomposite to enhance film adhesion on the glass surface. The photocatalytic activity under ultraviolet and simulated solar irradiation was examined. Further, the influence of different water matrices (milli-Q, river, lake, and seawater) and reactive species (h+, •OH, and e−) on the photocatalytic efficiency of the immobilised rGO/TiO2 nanocomposite was careful assessed. MB dye photocatalytic degradation was found to increase with increasing irradiation time for both irradiation sources. The immobilisation of prepared photocatalysts is very convenient for environment applications, due to easy separation and reusability, and the investigated rGO/TiO2-coated glass sheets demonstrated high efficiency in removing MB dye from an aqueous medium during five consecutive cycles.