Chao Xue

A facile strategy for the synthesis of hierarchical TiO2/CdS hollow sphere heterostructures with excellent visible light activity

A facile and efficient strategy for the synthesis of hierarchical TiO2/CdS hollow sphere (HS) heterostructures has been developed. Evaluation of the TiO2/CdS HS heterostructures for the degradation of rhodamine B (RhB) and methyl orange (MO) revealed that they exhibit excellent photocatalytic activity under visible light irradiation.

A facile one-step synthesis of three-dimensionally ordered macroporous N-doped TiO2 with ethanediamine as the nitrogen source

In this paper, three-dimensionally ordered macroporous (3DOM) N-doped anatase TiO2 (N-TiO2) photocatalysts with well-defined macroporous skeletons were prepared using a simple one-step colloidal crystal-templating method. Organic ammonia ethanediamine was used as the nitrogen source during preparation to enhance nitrogen incorporation into the TiO2 lattice. The photocatalytic performance of the as-prepared 3DOM N-TiO2 was investigated by measuring the degradation of rhodamine B (RhB) and the generation of H2 from water splitting under simulated visible-light conditions. In comparison with the pure TiO2 and N-doped TiO2, the results of photodegradation and photocatalytic hydrogen generation reactions showed that the 3DOM N-TiO2 sample exhibited excellent catalytic activity under visible-light irradiation. In addition, various analytical techniques have been used to characterize the crystal phase, morphology and optical absorption of the obtained samples. The results showed that the 3DOM N-TiO2 catalyst was successfully synthesized by the one-step colloidal crystal-templating method, and the as-prepared samples possessed well-defined 3DOM skeleton structure, high crystallinity and enhanced visible-light-driven photocatalytic activities.

Comprehensive investigation of the reciprocity of structure and enhanced photocatalytic performance in finned-tube structured TiO2/BiOBr heterojunctions

Finned-tube structured TiO2@BiOBr heterojunctions were synthesized via a facile and efficient solvothermal process. Field-emission scanning electron microscopy and transmission electron microscopy analyses demonstrated that the tunable uniform lamellar structured BiOBr nanoplates burgeoned from the surface of one-dimensional TiO2 nanotubes and constructed intimate interfacial junctions. The formation mechanism of the as-prepared TiO2@BiOBr heterojunctions was thus proposed. Owing to the combined effects of the intense visible light absorption, the efficient charge separation and lower recombination of photo-generated electron–hole pairs as well as larger specific surface area, the as-fabricated heterojunctions exhibited the best visible-light photocatalytic activity, structural stability and sustained cycling performance compared with the reported congeneric catalysts. Their degradation rate remained at 95.5% after seven cycles for the photodecomposition of RhB. A possible mechanism of the photocatalytic activity enhancement was also proposed based on the photocurrent measurements, the photoluminescence analysis and the radical trapping experiments. It revealed that the intimate interfacial junction could promote the separation of photo-generated charge carriers, simultaneously, both ·O2− and h+ acted as the main reactive species in the rapid degradation of RhB under visible-light irradiation.

Monodisperse Ag–AgBr nanocrystals anchored on one-dimensional TiO2 nanotubes with efficient plasmon-assisted photocatalytic performance

The broadening light absorption and efficient separation of photo-generated electron–hole pairs are crucial factors for the substantial applications of efficient artificial photocatalysts. Constructing novel nanoarchitectures with an appropriate interfacial junction and enhanced plasmonic fields exhibit promising behavior in photodegradation. Herein, we successfully synthesize a novel ternary Ag–AgBr/TiO2 plasmonic nanotube heterojunction photocatalyst by a facile deposition–precipitation strategy. Compared with the previously reported photocatalysts, the ternary Ag–AgBr/TiO2 plasmonic heterojunctions can thoroughly eliminate the organic pollutant RhB at an ultrafast degradation rate (the first-order reaction rate constant was calculated to be 0.1846 min−1). The main mechanism for the enhanced photocatalytic activity is that the unique tubular configuration not only provides a large specific surface area but also can contribute to the multiple diffractions and reflections of light and finally improve the light harvesting capability. Additionally, visible-light-driven AgBr anchored on the surface of TiO2 nanotubes, resulting in an intimate contact interface junction. Moreover, the stronger SPR effect of Ag nanoparticles significantly increases the production of photo-induced electron–hole pairs and effectively facilitates the plasmon-mediated interfacial electron transfer.

Anchoring Tailored Low-Index Faceted BiOBr Nanoplates onto TiO2 Nanorods to Enhance the Stability and Visible-Light-Driven Catalytic Activity

In this work, a fantastic one-dimensional (1D) BiOBr/TiO2 nanorod (NR) heterojunction composite was rationally proposed and designed from the perspective of molecular and interface engineering. The fabricated intimately connected interfacial heterojunction between two-dimensional BiOBr nanoplates and 1D TiO2 NRs acts as an interfacial nanochannel to promote efficient interfacial charge migration and separation of photogenerated electron-hole pairs. As a result, 1D BiOBr/TiO2 NR heterojunctions exhibited outstanding visible-light photocatalytic activities and sustained cycling performance. Under visible-light irradiation for 120 min, the reduction efficiency of Cr(VI) over the TB-2 sample (molar ratio: n(Ti)/n(Bi) = 2:1) is as high as 95.4% without adding any scavengers. Furthermore, the sample also shows excellent photodegradation activity of RhB with a much higher apparent rate constant of 0.49 min-1 and 88.5% total organic carbon removal ratio. Furthermore, the corresponding mechanism of enhanced photocatalytic activity is proposed according to comprehensively investigated results from photoluminescence spectroscopy, photoelectrochemical measurement analysis, and radical trapping experiments. This study provides an attractive avenue to design and fabricate highly efficient 1D NR heterojunction photocatalysts, which possessed a high application value in the field of environmental remediation, especially for wastewater purification.

Formation of three-dimensionally ordered macroporous TiO2@nanosheet SnS2 heterojunctions for exceptional visible-light driven photocatalytic activity

In this paper, a simple colloidal crystal-templating method assisted by a hydrothermal process has been proposed to prepare novel three-dimensionally ordered macroporous (3DOM) TiO2@nanosheet SnS2 heterojunction photocatalysts. The photoactivities of all the obtained samples were measured by the photodecomposition of rhodamine B (RhB), the photoreduction of Cr(VI) and photocatalytic hydrogen generation from water splitting. In comparison with pure SnS2 nanosheets and 3DOM TiO2, the 3DOM TiO2@SnS2 sample with a Sn/Ti molar ratio of 7.5 : 100 showed the highest photocatalytic activity for wastewater purification (kapp for RhB solution = 0.035 min−1 and for Cr6+ solution = 0.0845 min−1) and hydrogen generation under visible light irradiation. By means of ultraviolet-visible diffuse reflectance spectra (UV-vis DRS), photoluminescence (PL) spectra, transient photocurrent spectra, electron paramagnetic resonance (EPR) measurements and photocatalytic experiments, a suggested mechanism for the charge generation and transfer in the 3DOM TiO2@nanosheet SnS2 heterojunction was proposed. The improved charge separation and enhanced photocatalytic activity for the as-prepared TiO2@SnS2 composition can be attributed to the well-defined 3DOM heterojunction structure and the spatial transfer of the visible-light excited high energy electrons of SnS2 to TiO2. This work will provide a novel route to prepare highly active heterojunction photocatalysts and a new insight into the study of electron migration paths in TiO2@SnS2 composites.

Formation of BiOI/g-C 3 N 4 nanosheet composites with high visible-light-driven photocatalytic activity

Constructing binary heterojunctions is an important strategy to improve the photocatalytic performance of graphitic carbon nitride (g-C 3 N 4 ). In this paper, a novel g-C 3 N 4 nanosheet-based composite was constructed via in situ growth of bismuth oxyiodide (BiOI) nanoplates on the surface of g-C 3 N 4 nanosheets. The crystal phase, microstructure, optical absorption and textural properties of the synthesized photocatalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy (DRS), and nitrogen adsorption-desorption isotherm measurements. The BiOI/g-C 3 N 4 nanosheet composite showed high activity and recyclability for the photodegradation of the target pollutant rhodamine B (RhB). The conversion of RhB (20 mg L −1 ) by the photocatalyst was nearly 100% after 50 min under visible-light irradiation. The high photoactivity of the BiOI/g-C 3 N 4 nanosheet composite can be attributed to the enhanced visible-light absorption of the g-C 3 N 4 nanosheets sensitized by BiOI nanoplates as well as the high charge separation efficiency obtained by the establishment of an internal electric field between the n-type g-C 3 N 4 and p-type BiOI. Based on the characterization and experimental results, a double-transfer mechanism of the photoinduced electrons in the BiOI/g-C 3 N 4 nanosheet composite was proposed to explain its activity. This work represents a new strategy to understand and realize the design and synthesis of g-C 3 N 4 nanosheet-based heterojunctions that display highly efficient charge separation and transfer.