Bing-Xin Zhou

Dual role of monolayer MoS2 in enhanced photocatalytic performance of hybrid MoS2/SnO2 nanocomposite

The enhanced photocatalytic performance of various MoS2-based nanomaterials has recently been observed, but the role of monolayer MoS2 is still not well elucidated at the electronic level. Herein, focusing on a model system, hybrid MoS2/SnO2 nanocomposite, we first present a theoretical elucidation of the dual role of monolayer MoS2 as a sensitizer and a co-catalyst by performing density functional theory calculations. It is demonstrated that a type-II, staggered, band alignment of ∼0.49 eV exists between monolayer MoS2 and SnO2 with the latter possessing the higher electron affinity, or work function, leading to the robust separation of photoexcited charge carriers between the two constituents. Under irradiation, the electrons are excited from Mo 4d orbitals to SnO2, thus enhancing the reduction activity of latter, indicating that the monolayer MoS2 is an effective sensitizer. Moreover, the Mo atoms, which are catalytically inert in isolated monolayer MoS2, turn into catalytic active sites, making the mo...

Facile ion-exchange synthesis of mesoporous Bi2S3/ZnS nanoplate with high adsorption capability and photocatalytic activity.

Novel Bi2S3/ZnS nanoplates have been successfully prepared by simple reflux and cation exchange reaction between the preformed ZnS spheres and Bi(NO3)3·5H2O. The synthesized Bi2S3/ZnS nanoplates are mesoporous structures, possess a high specific surface area of 101.30m(2)/g and exhibit high adsorption capability and photocatalytic activity for methylene blue (MB) degradation under UV light irradiation. The high adsorption capability and photocatalytic activity can be ascribed to the fact that the formation of Bi2S3/ZnS nanoplates with large specific surface area provides more reactive sites and facilitates the separation of photogenerated electron-hole pairs. The possible formation mechanism of Bi2S3/ZnS nanoplates is proposed based on the time-dependent observation. Moreover, a tentative mechanism for degradation of MB over Bi2S3/ZnS has been proposed involving OH radical and photoinduced holes as the active species, which is confirmed by using methanol or ammonium oxalate as scavengers. This work provides a cost-effective method for large-scale synthesis of composite with controlled architectural morphology and highly promising applications in photocatalysis.

Tuning near-gap electronic structure, interface charge transfer and visible light response of hybrid doped graphene and Ag3PO4 composite: Dopant effects.

The enhanced photocatalytic performance of doped graphene (GR)/semiconductor nanocomposites have recently been widely observed, but an understanding of the underlying mechanisms behind it is still out of reach. As a model system to study the dopant effects, we investigate the electronic structures and optical properties of doped GR/Ag3PO4 nanocomposites using the first-principles calculations, demonstrating that the band gap, near-gap electronic structure and interface charge transfer of the doped GR/Ag3PO4(100) composite can be tuned by the dopants. Interestingly, the doping atom and C atoms bonded to dopant become active sites for photocatalysis because they are positively or negatively charged due to the charge redistribution caused by interaction. The dopants can enhance the visible light absorption and photoinduced electron transfer. We propose that the N atom may be one of the most appropriate dopants for the GR/Ag3PO4 photocatalyst. This work can rationalize the available experimental results about N-doped GR-semiconductor composites, and enriches our understanding on the dopant effects in the doped GR-based composites for developing high-performance photocatalysts.

Two-Dimensional MoS2-Graphene-Based Multilayer van der Waals Heterostructures: Enhanced Charge Transfer and Optical Absorption, and Electric-Field Tunable Dirac Point and Band Gap

Multilayer van der Waals (vdW) heterostructures assembled by diverse atomically thin layers have demonstrated a wide range of fascinating phenomena and novel applications. Understanding the interlayer coupling and its correlation effect is paramount for designing novel vdW heterostructures with desirable physical properties. Using a detailed theoretical study of two-dimensional (2D) MoS2-graphene (GR)-based heterostructures based on state-of-the-art hybrid density functional theory, we reveal that for 2D few-layer heterostructures, vdW forces between neighboring layers depend on the number of layers. Compared to that in the bilayer, the interlayer coupling in trilayer vdW heterostructures can significantly be enhanced by stacking the third layer, directly supported by short interlayer separations and more interfacial charge transfer. The trilayer shows strong light absorption over a wide range (<700 nm), making it great potential for solar energy harvesting and conversion. Moreover, the Dirac point of GR ...

Enhanced photocatalytic activity of hexagonal flake-like Bi2S3 / ZnS composites with a large percentage of reactive facets

Selectively exposing surfaces with high reactivity is an effective strategy to enhance the photocatalytic activity of semiconductor photocatalysts. We report the facile synthesis of hexagonal flake-like Bi2S3/ZnS composites with a large percentage of reactive exposed {2 2 1} facets by tuning only the molar ratios of Bi to Zn. The samples exhibit enhanced optical absorption and red shift of absorption edge. The Bi2S3/ZnS composites with hexagon morphology display superior photocatalytic degradation of methylene blue (MB), faster than that with pure Bi2S3 and pure ZnS by a factor of 7.1 and 3.6, respectively. The enhanced photocatalytic activity can be attributed to the highly reactive {2 2 1} exposed facets and the more efficient separation of photogenerated electron–hole pairs is due to the interface of the hetero-junction. Furthermore, a tentative mechanism for photodegradation of MB over Bi2S3/ZnS composites has been proposed involving the photogenerated holes and ⋅OH radicals as the main active species, which is confirmed by using different scavengers. The novel constructed Bi2S3/ZnS composite is expected to be an attractive candidate as a photocatalyst for environmental purification and energy conversion.