Tingyu Wang

Facile solvothermal synthesis of BiOCl–TiO2 heterostructures with enhanced photocatalytic activity

BiOCl–TiO2 heterostructures with different Bi to Ti molar ratios were synthesized via a facile one-pot solvothermal process. The as-synthesized BiOCl–TiO2 heterostructures included TiO2 nanoparticles deposited on the surface of BiOCl nanoplates. X-ray photoelectron spectroscopy results revealed the TiO2 of BiOCl–TiO2 heterostructures doped with Bi3+, reduced the band gap energy of the sample. The photocatalytic efficiencies were evaluated by degradation of methylene blue dye under simulated sunlight illumination. Results indicated that the BiOCl–TiO2 heterostructures with Bi : Ti = 1 : 3 exhibited the highest photocatalytic efficiency, which is 73.5 times and 8.5 times higher than that of single phase BiOCl and TiO2, respectively. In addition, the radical species involved in the degradation process have been investigated by scavenger experiments. Finally, a new mechanism for the photocatalytic action of the BiOCl–TiO2 heterostructures was put forward.

Dependence of infrared absorption properties on the Mo doping contents in MxWO3 with various alkali metals

A series of molybdenum-doped tungsten bronzes with various alkali metals were synthesized by a solvothermal process using ethanol and acetic acid as solvents. All the X-ray diffraction (XRD) peaks for the samples could be indexed as the corresponding types of hexagonal tungsten bronzes with the general formula, MxWO3, where M denotes an alkali metal. Targeted research on cesium tungsten bronze indicates that the actual atomic ratio of Cs to W (x) could be influenced by the introduction of molybdenum, which has a critical effect on the infrared absorption properties. Optical tests show that molybdenum-doping is an effective process, with respect to enhancing the absorption of infrared and the conversion efficiency of light energy to heat energy, for tungsten bronzes with various alkali metals. The optimum starting Mo/W (mol) ratios for obtaining high infrared absorption properties were 0.01 for sodium and potassium tungsten bronzes and 0.03 for rubidium and cesium tungsten bronzes. Among the samples, doped cesium tungsten bronze has the strongest properties.

Synthesis and infrared shielding properties of molybdenum-containing ammonium tungsten bronzes

A series of molybdenum-containing ammonium tungsten bronzes was synthesized by a solvothermal process at 200 °C for 72 h using ethylene glycol, acetic acid, ammonium tungstate and ammonium molybdate as starting materials. All the diffraction peaks of XRD for the samples synthesized with starting Mo/W (mol) = 0–0.2 could be rough indexed as a hexagonal ammonium tungsten bronze with the formula of (NH4)0.33WO3, which was accompanied by a shift of the main peaks after the introduction of molybdenum and a split peak for starting Mo/W (mol) = 0.1. The nitrogen content, based on both the thermogravimetry and X-ray photoelectron spectroscopy, rose with the increase of molybdenum content. Optical properties were evaluated using Fourier transform infrared spectroscopy, which proved that the molybdenum-containing ammonium tungsten bronzes could shield infrared rays better than the sample without molybdenum. The shield efficiency was related to the content of molybdenum. The optimum starting Mo/W (mol) to obtain high infrared shielding properties was 0.1. This sample consisted of uniform rods of ca. 50 nm in diameter emerging from the agglomerates.