Junpeng Wang

Template-free synthesis of mesoporous anatase titania hollow spheres and their enhanced photocatalysis

Monodispersed mesoporous anatase titania (TiO2) hollow microspheres with controllable morphology and size are prepared via thioglycolic acid (TGA) chemically induced self-assembly for the first time. The formation process of TiO2 hollow spheres consists of three steps: hydrolysis of titanium butoxide (TBT) forming Ti-oxo clusters followed by connecting TGA via hydrogen bonding, assembly of the Ti-oxo clusters to solid spheres, and transformation of the TiO2 solid spheres into hollow spheres through the synergistic effect of thermodynamic (Ostwald ripening process) and kinetic (gas release) factors. TGA molecules firstly provide acidic conditions slowing down the hydrolysis rate of TBT, then control the formation of solid spheres, and finally create hollow structures. The prepared TiO2 hollow sphere with mesoporous structure has a large specific surface area (292.20 m2 g−1). Photocatalytic degradation of methyl orange (MO) by the TiO2 hollow spheres after reflux treatment improves significantly, owing to removal of TGA molecules from the TiO2 hollow spheres. Moreover, photocatalytic water splitting of highly crystalline TiO2 hollow spheres decorated with Pt nanoparticles exhibits an impressive performance for producing H2 (0.477 mmol h−1).

Fabrication and Photocatalytic Activity of Tunable Triangular- and Circular-Like Ag/AgCl Nanoplates

Triangular- and circular-like Ag/AgCl nanoplates with various edge length and thickness have been successfully synthesized by a facile in situ oxidation process. Uniform Ag triangular nanoplates with tunable sizes and thicknesses obtained by adjusting the adding amounts of trisodium citrate and polyvinylpyrrolidone (PVP) were employed as Ag precursors to form triangular- and circular-like Ag/AgCl heterostructures by changing the adding amounts of FeCl3 in the reaction process. The morphological evolution mechanism of Ag nanoplates and Ag/AgCl heterostructures was discussed. It is clear that the morphologies of Ag/AgCl products can be gradually converted from the large and thick triangular-like nanoplates into the small and thin circular-like ones as the AgCl ratio increasing from 5 to 100%, which can be mainly assigned to the synergistic effect of the oxidation of Fe3+ and the etching action of Cl-. The photocatalytic results indicate that Ag/AgCl nanoplates with different ratios of AgCl can exhibit good photocatalytic activity for degradation of methyl orange (MO) pollutant under ultraviolet-light-driven (UVD) and visible-light-driven (VLD) irradiation, respectively. The Ag/AgCl nanoplates with an AgCl ratio of 30% have the superior photocatalytic activity with the photocatalytic efficiency calculated to be 83.5% within 160 min under UVD irradiation and 53.6% within 240 min under VLD irradiation, respectively, owing to the combination of the favorable crystallinity, excellent photoabsorption, and the efficient separation of the photo-induced carriers between Ag and AgCl.

Composited BiOI Nanoplatelets on Carbon Fibers Towards Enhanced Photocatalysis

BiOI nanoplatelets were successfully grown on carbon fibers (CFs) surface, which had been activated in acid and alkaline solution (CFs-AC and CFs-AL). The BiOI microspheres composed of nanoplatelets were distributed relatively equally on CFs surface after acidizing while the CFs treatment by alkaline solution the BiOI nanoplatelets cannot combined tightly with CFs. The as-prepared BiOI/CFs was characterized by X-ray diffraction, scanning electron microscopy and UV-vis diffuse reflectance spectroscopy. The possible mechanism of BiOI/CFs formation was attributed to the electrostatic adsorption in reaction process. The photocatalytic of the as-prepared samples (CFs-AC and CFs-AL) were evaluated by degradation of rhodamine B (RhB) under visible light irradiation at room temperature. CFs-AC possessed higher photocatalytic activity than that of CFs-AL, pure CFs and BiOI. The mechanism of the enhancement of photocatalytic process was discussed.