Tengfei Zhou

Controlled strategy to synthesize SnO2 decorated SnS2 nanosheets with enhanced visible light photocatalytic activity

Novel SnO2 nanoparticle-decorated SnS2 nanosheets were synthesized via a one-pot solvothermal process using SnCl4·5H2O and CH4N2S as precursors. SnS2@SnO2 nanosheets were characterized by XRD, TEM, FESEM, XPS and UV-vis diffuse reflectance spectra (DRS). The band-gap of SnO2@SnS2 can be easily tuned by the controlled experimental strategy. Anisole and ethanol with different volume ratios were used as binary solvent to tune the composition of SnS2@SnO2 nanocomposites (NCs) continuously and the composites gradually change from hexagonal SnS2 into tetragonal SnO2. All of the SnS2@SnO2 nanosheets exhibited enhanced visible light photocatalytic activity, which was remarkably superior to SnS2, SnO2 and Degussa P-25. The obtained SnS2@SnO2 NCs with Vethanol/Vanisole = 1 : 2 showed the best photocatalytic capability. Furthermore, the formation mechanism of SnS2@SnO2 nanosheets has also been discussed.

Mass production and photocatalytic activity of highly crystalline metastable single-phase Bi20TiO32 nanosheets.

Highly crystalline metastable bismuth titanate (Bi₂₀TiO₃₂) nanosheets are prepared via a simple green wet chemical route for the first time. The Bi₂₀TiO₃₂)photocatalysts were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive spectrum analysis (EDS), X-ray diffraction (XRD), N₂ adsorption-desorption (BET), and UV-vis diffuse reflectance spectroscopy (DRS). Inspiringly, Bi₂₀TiO₃₂ nanosheets showed high photocatalytic activity for the degradation of nonbiodegradable azo dye under simulated sunlight and visible-light irradiation. The experimental results showed that the photocatalytic activity of the Bi₂₀TiO₃₂ nanosheets was superior to the commercial Degussa P25 TiO₂, and demonstrated that the morphology and crystal structure have a distinct effect on the photocatalytic activity. The reasons for the high photocatalytic activity and the formation mechanism of Bi₂₀TiO₃₂ nanosheets are also discussed.

Self-assembly of layered wurtzite ZnS nanorods/nanowires as highly efficient photocatalysts

Unusually extended and oriented wurtzite ZnS nanorods/nanowires have been successfully synthesized by a one-pot wet chemical method. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and UV-vis diffuse reflectance spectroscopy (DRS). These nanorods and nanowires are well defined by stacking ZnS nanosheets layer-by-layer along the [0001] direction, and each layer of these nanorods (or nanowires) is a single crystalline ZnS wurtzite structure. A possible formation mechanism for the growth of the ZnS NRs has been proposed. More importantly, the layered ZnS nanorods/nanowires are confirmed to possess an extraordinary photocatalytic ability for the photodegradation of non-biodegradable brilliant red X-3B azo dye under UV-light irradiation.

Glutatione modified ultrathin SnS2 nanosheets with highly photocatalytic activity for wastewater treatment

L-Glutatione (GSH) modified ultrathin SnS2 nanosheets were successfully synthesized via a one-pot, facile and rapid solvothermal approach. During the process, the GSH not only served as the sulfur sources, the structure-directing agent, but also as the surface modified ligands. The as-synthesized samples mainly consist of ultrathin nanosheets with the thickness of about 10 nm. Inspiringly, even under the visible light (λ > 420 nm) irradiation, the as-synthesized products exhibited highly photocatalytic activities for both the degradation of methyl orange (MO) and the reductive conversion of Cr (VI) in aqueous solution. The superior performance was presented by completely removed the methyl orange and aqueous Cr(VI) in 20 min and 60 min, respectively. It was much higher than the pure samples, which suggested that these obtained photocatalysts have the potential for wastewater treatment in a green way. The high-efficiency of photocatalytic properties could attribute to the ultrathin size of the photocatalysts and the chelation between GSH and Sn (IV), which have the advantages of electron–hole pairs separation. Moreover, modified organic compounds with common electron donors would also enhance the spectral response even to the near infrared region through ligand-to-metal charge transfer (LMCT) mechanism.

Surfactant-mediated synthesis of single-crystalline Bi3O4Br nanorings with enhanced photocatalytic activity

We present a surfactant-mediated approach to the production of single-crystal Bi3O4Br nanorings via a simple solvothermal method. The ring-like morphology is rare among bismuth oxyhalides, and the reaction pathways are superior to traditional chemical transformations. In detail, Bi3O4Br nanorings are prepared in three stages: (1) the formation of precursors, (2) selective etching and (3) Ostwald ripening. During these steps, the extra usage of templates is avoided and a series of useful intermediates are obtained. Besides, this method can be extended to fabricate other bismuth oxyhalide nanorings. Under visible-light irradiation, all of our samples are photo-activated. The Bi3O4Br nanorings exhibit an efficient oxygen-evolution rate (72.54 μmol h−1) and pollutant degradation rate (4.71 × 10−2 g min−1 m−2), which can be attributed to their unique ring structures and band potentials. Thus, the surfactant-mediated chemical conversion strategy not only paves a new way to enhance the photocatalytic activity of bismuth oxyhalides, but also provides an important large-scale route for designing other nanomaterials with ring-like structures.

Generalized Synthesis of Ternary Sulfide Hollow Structures with Enhanced Photocatalytic Performance for Degradation and Hydrogen Evolution

A series of ternary sulfide hollow structures have been successfully prepared by a facile glutathione (GSH)-assisted one-step hydrothermal route, where GSH acts as the source of sulfur and bubble template. We demonstrate the feasibility and versatility of this in situ gas-bubble template strategy by the fabrication of novel hollow structures of MIn2S4 (M = Cd, Zn, Ca, Mg, and Mn). Interestingly, with the reaction time varying, the hierarchical CdIn2S4 microspheres with controlled internal structures can be regulated from yolk-shell, smaller yolk-shell (yolk-shell with shrunk yolk), hollow, to solid. Under visible-light irradiation, all of our prepared CdIn2S4 samples with different morphologies were photoactivated. In virtue of the appealing hierarchical hollow structure, the yolk-shell-structured CdIn2S4 microspheres exhibited the optimal photocatalytic activity and excellent durability for both the X3B degradation and H2 evolution, which can be ascribed to the synergy-promoting effect of the small crystallite size together with the unique structural advantages of the yolk-shell structure. Thus, we hypothesize that this proof-of-concept strategy paves an example of rational design of hollow structured ternary or multinary sulfides with superior photochemical performance, holding great potential for future multifunctional applications.

Construction of Hierarchical MoSe2 Hollow Structures and Its Effect on Electrochemical Energy Storage and Conversion

Metal selenides have attracted increased attention as promising electrode materials for electrochemical energy storage and conversion systems including metal-ion batteries and water splitting. However, their practical application is greatly hindered by collapse of the microstructure, thus leading to performance fading. Tuning the structure at nanoscale of these materials is an effective strategy to address the issue. Herein, we craft MoSe2 with hierarchical hollow structures via a facile bubble-assisted solvothermal method. The temperature-related variations of the hollow interiors are studied, which can be presented as solid, yolk-shell, and hollow spheres, respectively. Under the simultaneous action of the distinctive hollow structures and interconnections among the nanosheets, more intimate contacts between MoSe2 and electrolyte can be achieved, thereby leading to superior electrochemical properties. Consequently, the MoSe2 hollow nanospheres prepared under optimum conditions exhibit optimal electrochemical activities, which hold an initial specific capacity of 1287 mA h g-1 and maintain great capacity even after 100 cycles as anode for Li-ion battery. Moreover, the Tafel slope of 58.9 mV dec-1 for hydrogen evolution reaction is also attained.

Biomimetic Structure Design and Construction of Cactus-like MoS2/Bi19Cl3S27 Photocatalyst for Efficient Hydrogen Evolution

Cacti grown in arid areas have developed intrinsic water management systems, inspired by the cactus which has survived cruel natural selection, uncommon cactus-like MoS2/Bi19Cl3S27 heterostructures have been successfully constructed in this work. Resembling the trichome and epidermis of a cactus stem, vertically aligned MoS2 along with a carbon species hydrolyzed from glucose on Bi19Cl3S27 comprised the unique biomimetic structure. During the photocatalytic process of MoS2/Bi19Cl3S27 heterostructures, the characteristic biomimetic structure endows the heterostructures with greatly enhanced light adsorption and charge separation capabilities, the whole hydrogen evolution reaction was boosted by the combination of optimized charge and mass transfer paths, like the plant morphogenesis of a cactus which plays a significant role in mucilage-based energy-transmission. As a consequence, the improved photocatalytic H2 evolution rate reaches up to 876.6 μmol g−1 h−1 with an optimal loading of 5 wt% MoS2. The successful preparation of biomimetic structured MoS2/Bi19Cl3S27 samples with good stability shows that bismuth-based materials have great potential for applications in energy conversion systems, while providing enlightenment for the design of other biomimetic structured nanomaterials.