Photocatalytic degradation of bisphenol A induced by dense nanocavities inside aligned 2D-TiO2 nanostructures

Abstract

The preparation of materials with aligned porosity in the nanometer range is of technological importance for a wide range of applications in molecular filtration, biomaterials and catalysis. Herein we present the advantages offered by cryo-lyophilisation technique as a smart and green non-standard concept to produce dense regular polyhedral nanocavities inside the 2D TiO 2 nanosheets. Hierarchical morphologies of nanocavities start to appear at temperature higher than 800 °C and are strongly influenced by polymorph TiO 2 evolution competing reactions. The small angle X-ray scattering (SAXS) analysis confirms self-assembled 3D nanocavities with size range from 5 to 10 nm in both length and width, and depth ~ 3.6 nm formed after realising of the confined ice-water. It was found that nanocavities enhance significantly the absorption properties of TiO 2 in the UV region, thereby providing a new approach to increase the photoreactivity of 2D TiO 2 nanosheets. The annealed precursors containing aqueous solution of peroxo polytitanic acid (PPTA) at 800 °C exhibited the highest photoactivity in degrading bisphenol A (BPA) due to evenly distributed nanocavities inside single anatase TiO 2 nanocrystals interconnected and aligned onto the 2D TiO 2 nanosheet arrays.

The relationship between microstructure and photocatalytic behavior in lanthanum-modified 2D TiO2 nanosheets upon annealing of a freeze-cast precursor

“…For materials Ti_La_650 and Ti_La_800, the E g value was below the reference anatase sample (E g ¼ 3.24 eV) and non-modied 2D TiO 2 nanosheets obtained by the same method. 27 The best performance in 4-CP photocatalytic decomposition was achieved with Ti_La_650 material that has the lowest E g and related redshi of the optical absorption. The higher photocatalytic efficiency of the Ti_La_650 catalyst can be explained by substitutional incorporation of La 3+ into the anatase lattice, which has a clear positive effect on the photocatalytic activity under UV light irradiation.…”

“…La-modied TiO 2 nanosheets were prepared by a freeze-casting method [24][25][26][27] using aqueous colloids of peroxo-polytitanic acid (PPTA) and La(NO 3 ) 3 (see Scheme 1). In a typical experiment, 4.80 g of titanyl sulfate was dissolved in 150 mL of distilled water at 35 C (step 1).…”

“…In previous research, we found that the binuclear adducts were formed by mixing TiOSO 4 as the source of Ti 4+ and H 2 O 2 (Scheme 1). 25,27 These adducts contain the planar Ti-O-O-Ti grouping where the Ti atoms are bridged by m-oxygen and two m-peroxy groups (Fig. 3a).…”

“…Recently, we have published more insights regarding the capability of the freeze-casting procedure to produce TiO 2 nanomaterial with a layered structure. [24][25][26][27] Modication of the PPTA precursor by adding a noble metal (Ag and Au) or lanthanide element (Nd) does not change titania morphology and leads to a porous 2D TiO 2 structure identical to the structure of nonmodied TiO 2 samples. 56 SEM studies of the La-modied 2D TiO 2 nanosheets (i.e., Ti_La_500, Ti_La_650, Ti_La_800 and Ti_La_950) are in line with our previously published results.…”

Using Ice Crystals to Template Nanocavities on the Surface of Au Modified 2D TiO2 Nanosheets: Visible Light Driven Water Splitting

“…Fig. 1d shows dense regular polyhedral nanocavities inside the 2D TiO 2 nanosheets with size ranging from 5 to 78 nm in both, length and width, and depth of about 8 nm (Fig.1 c-d) [4]. The Au NPs with the size around 2-5 nm were anchored along the hollow patterned surface of the [Au_2D TiO 2 ]/800.…”