Yuhua Dai

Preparation of graphene/TiO2 composites by nonionic surfactant strategy and their simulated sunlight and visible light photocatalytic activity towards representative aqueous POPs degradation

A series of graphene/TiO2 composites were fabricated using a single-step nonionic surfactant strategy combined with the solvothermal treatment technique. Their phase structure, morphology, porosity, optical absorption property, as well as composition and structure, were characterized. The as-prepared composites were successfully applied to degrade aqueous persistent organic pollutants (POPs) such as rhodamine B, aldicarb, and norfloxacin in simulated sunlight (λ>320 nm) and visible light (λ>400 nm) irradiation. The degradation mechanism and kinetics of aqueous POPs were studied in detail. The mineralization of aqueous POPs and the recyclability of the composites were also tested in the same condition.

Fabrication of carbon nitride nanotubes by a simple water-induced morphological transformation process and their efficient visible-light photocatalytic activity

Carbon nitride nanotubes (C3N4 NTs) were synthesized based on the nanosheets roll-up mechanism by a simple water-induced morphological transformation process using graphitic carbon nitride (g-C3N4) as a precursor. Water was used as the phase-transfer reagent, making the preparation process environmentally friendly. The visible-light photocatalytic activity of the as-prepared C3N4 NTs significantly increased compared to bulk g-C3N4 and g-C3N4 nanosheets toward rhodamine B degradation and hydrogen evolution from water-splitting. This result can be attributed to the high photogenerated carrier transfer efficiency, excellent mass transfer capability, sufficient active sites, and enhanced light utilization efficiency of C3N4 NTs.

Novel hybrid Sr-doped TiO2/magnetic Ni0.6Zn0.4Fe2O4 for enhanced separation and photodegradation of organics under visible light

Titanium dioxide (TiO2) has been intensively used as a photocatalyst for the degradation of organic pollutants in water, but is typically obstacle by a low efficiency, costly separation, limited visible light response, and poor recyclability. Herein, we provided a reliable method to simultaneously tackle these four obstacles by developing an integrated and multifunctional hybrid photocatalyst/magnetic material, i.e., Sr–TiO2/Ni0.6Zn0.4Fe2O4. This novel hybrid not only demonstrated a high efficiency (90–100%) and a good cycling performance (90% maintenance) for photodegradation of bisphenol A (BPA) under both UV and visible light irradiation, but it can also efficiently work at a wide pH range (4–10) and can be easily separated from water for reuse only by introducing an external magnetic field. The materials structure-to-activity correlation has also been investigated. It was found that doping Sr2+ and a coupling magnetic material with TiO2 could extend the visible light response and create active defects in TiO2, which were responsible for the nearly three times higher activity than that of commercial TiO2(P25) under visible light. On the other hand, doping excessive Sr2+ lowered the surface area, enlarged the crystalline size and caused particle aggregation; thus, leading to a decrease in photocatalytic activity of the hybrid. These further modifications in the hybrid materials can provide a competitive alternative to control the organic pollutants in waste water.

Fabrication of porous g-C 3 N 4 and supported porous g-C 3 N 4 by a simple precursor pretreatment strategy and their efficient visible-light photocatalytic activity

Porous g-C 3 N 4 and supported porous g-C 3 N 4 were fabricated for the first time by a simple strategy using pretreated melamine as a raw material and pretreated quartz rod as a substrate. The formation of a richly porous microstructure can be attributed to the co-existence of different pore-fabricating units in the preparation system for porous g-C 3 N 4 . The richly porous microstructure endowed the as-prepared porous g-C 3 N 4 with an excellent photocatalytic activity. The as-prepared supported porous g-C 3 N 4 exhibited considerable stability because of the existence of chemical interaction between porous g-C 3 N 4 and the quartz rod substrate. The photocatalytic activity of the supported porous g-C 3 N 4 was competitive with that of porous g-C 3 N 4 in powder form because neither the surface migration of photogenerated electrons nor the diffusion of the target organic pollutant were affected by the construction of the quartz rod reactor. The photocatalytic activity of the as-prepared porous g-C 3 N 4 and supported porous g-C 3 N 4 was preliminarily evaluated by the treatment of single-component organic wastewater under visible-light irradiation. Subsequently, the as-prepared porous g-C 3 N 4 was further applied in conventional hydrogen evolution and a new system for simultaneous hydrogen evolution with organic-pollutant degradation. The hydrogen yield and degradation efficiency both increased with increasing photocatalytic activity of the as-prepared materials in the system for simultaneous hydrogen evolution with organic-pollutant degradation.

Fabrication of highly dispersed platinum-deposited porous g-C3N4 by a simple in situ photoreduction strategy and their excellent visible light photocatalytic activity toward aqueous 4-fluorophenol degradation

A series of highly dispersed platinum-deposited porous g-C 3 N 4 (Pt/pg-C 3 N 4 ) were successfully fab-ricated by a simple in situ photoreduction strategy using chloroplatinic acid and porous g-C 3 N 4 as precursors. Porous g-C 3 N 4 was fabricated by a pretreatment strategy using melamine as a raw ma-terial. The morphology, porosity, phase, chemical structure, and optical and electronic properties of as-prepared Pt/pg-C 3 N 4 were characterized. The photocatalytic activity of as-prepared Pt/pg-C 3 N 4 was preliminarily evaluated by the degradation of aqueous azo dyes methyl orange under visible light irradiation. The as-prepared Pt/pg-C 3 N 4 were further applied to the degradation and mineral-ization of aqueous 4-fluorophenol. The recyclability of Pt/pg-C 3 N 4 was evaluated under four con-secutive photocatalytic runs.