Reusable Platinum-Deposited Anatase/Hexa-Titanate Nanotubes: Roles of Reduced and Oxidized Platinum on Enhanced Solar-Light-Driven Photocatalytic Activity

A new class of photocatalysts, referred to as Pt(0)- or Pt­(IV)-deposited anatase/hexa-titanate nanotubes (Pt(0)-TNTs-600 and Pt­(IV)-TNTs-600), were prepared through a three-step process: hydrothermal conversion of commercial TiO₂ to titanate nanotubes and subsequent deposition of Pt and calcination. At the optimal Pt dosage (0.1 wt %) and calcination temperature (600 °C), Pt(0)-TNTs-600 showed the highest photocatalytic activity for degrading phenanthrene. The apparent pseudo-first order rate constant (<i>k</i>₁) was determined to be 0.12 h^–1, which was ∼2 and 3 times of that for Pt­(IV)-TNTs-600 and P25. TEM, XRD, FTIR, and XPS analyses indicate that Pt(0)-TNTs-600 is a composite of anatase and hexa-titanate with metallic Pt deposited, where Pt facilitates transport of photogenerated electrons, thus inhibiting recombination of the electron–hole pairs. Moreover, DRS UV–vis analysis revealed a narrower optical energy gap of materials, resulting in enhanced absorbance in the visible region. The new photocatalyst could also produce more reactive oxygen species, i.e. ·OH, than the P25 and pristine TNTs. The material can be reused in multiple cycles of water treatment operations (with almost no activity loss after six consecutive cycles). The new photocatalyst appears promising for efficient photodegradation of a host of organic pollutants in water under solar light

High-Capacity and Photoregenerable Composite Material for Efficient Adsorption and Degradation of Phenanthrene in Water

We report a novel composite material, referred to as activated charcoal supported titanate nanotubes (TNTs@AC), for highly efficient adsorption and photodegradation of a representative polycyclic aromatic hydrocarbon (PAH), phenanthrene. TNTs@AC was prepared through a one-step hydrothermal method, and is composed of an activated charcoal core and a shell of carbon-coated titanate nanotubes. TNTs@AC offered a maximum Langmuir adsorption capacity of 12.1 mg/g for phenanthrene (a model PAH), which is ∼11 times higher than the parent activated charcoal. Phenanthrene was rapidly concentrated onto TNTs@AC, and subsequently completely photodegraded under UV light within 2 h. The photoregenerated TNTs@AC can then be reused for another adsorption–photodegradation cycle without significant capacity or activity loss. TNTs@AC performed well over a wide range of pH, ionic strength, and dissolved organic matter. Mechanistically, the enhanced adsorption capacity is attributed to the formation of carbon-coated ink-bottle pores of the titanate nanotubes, which are conducive to capillary condensation; in addition, the modified microcarbon facilitates transfer of excited electrons, thereby inhibiting recombination of the electron–hole pairs, resulting in high photocatalytic activity. The combined high adsorption capacity, photocatalytic activity, and regenerability/reusability merit TNTs@AC a very attractive material for concentrating and degrading a host of micropollutants in the environment