From MoS2Microspheres to α-MoO3Nanoplates: Growth Mechanism and Photocatalytic Activities

Efficient removal of cytotoxic drugs from wastewater by single-stage combined photocatalysis-algae treatment process

In this study, the efficiency of a single-stage combined photocatalysis-algae treatment process in the removal of the anticancer drug, flutamide (FLU), from aqueous solution has been evaluated. The removal abilities of the individual blue-green alga (Anabaena sp.), nano-sized MoS₂ photocatalyst under visible light irradiation, and combined photocatalysis-algal treatment process were investigated. Using response surface optimization technique, 85.1% of the FLU removal was achieved at the optimum conditions of pH 7.0, nanophotocatalyst dose of 15.23 mg and 12.12 mL of the alga in 30 min. Compared to the individual biological and chemical treatment methods, a higher FLU removal efficiency was obtained at a shorter reaction time by using the combined treatment system. Kinetics study showed that FLU removal by the algal treatment, photocatalysis, and the combined processes followed the modified Freundlich, pseudo-first-order, and nonlinear sigmoidal kinetic models, respectively. The results indicate that a synergistic effect appears when algal treatment process and photocatalysis are performed simultaneously. The novel combined system is a low-cost and efficient microalgae-based technology for the removal of cytotoxic compounds from wastewaters.

Oxidation of NO x Using Hydrogen Peroxide Vapor over Mo/TiO2

xMo/TiO₂ catalysts (x = 1, 2, 3, and 4%) were prepared using the coprecipitation method in the present study. The coprecipitation method was used in the thermal catalytic decomposition of H₂O₂ steam to treat NO _x at a low temperature range (80-160 °C). Several characterization techniques have been employed, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller measurements, transmission electron microscopy (TEM), scanning electron microscopy and energy-dispersive X-ray spectrometry (SEM-EDXS), and Fourier transform infrared spectroscopy. The activity tests showed that the incorporation of molybdenum into TiO₂ led to a significant increase in the catalytic oxidation of NO, and under the condition of H₂O₂/NO = 6:1 (molar ratio), the NO _x removal rate of 2% Mo/TiO₂ is the highest, reaching 92.56%. XRD, TEM, and SEM-EDXS analyses showed that Mo was well dispersed on the surface of an anatase-phase TiO₂. XPS analysis indicated that Mo mixed with slag mainly existed in the form of Mo⁶⁺. Moreover, in comparison with the mostly reported SCO catalysts, used for the elimination of NO, the prepared Mo/TiO₂ catalyst showed excellent stability and sulfur resistance.

Facile Synthesis of a Z-Scheme ZnIn2S4/MoO3 Heterojunction with Enhanced Photocatalytic Activity under Visible Light Irradiation

Employing a visible-light-driven direct Z-scheme photocatalytic system for the abatement of organic pollutants has become the key scientific approach in the area of photocatalysis. In this study, a highly efficient Z-scheme ZnIn2S4/MoO3 heterojunction was prepared through the hydrothermal method, followed by the impregnation technique that facilitates the formation of an interface between the two phases for efficient photocatalysis. The structural, optical, and surface elemental composition and morphology of the prepared samples were characterized in detail through X-ray diffraction, UV-vis diffuse reflectance spectra, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results indicate that the composite materials have a strong intimate contact between the two phases, which is beneficial for the effective separation of photoinduced charge carriers. The visible-light-mediated photocatalytic activity of the samples was tested by studying the degradation of methyl orange (MO), rhodamine B (RhB), and paracetamol in aqueous suspension. An optimum loading content of 40 wt % ZnIn2S4/MoO3 exhibits the best degradation efficiency toward the above pollutants compared to bare MoO3 and ZnIn2S4. The improved photocatalytic activity could be ascribed to the efficient light-harvesting property and prolonged charge separation ability of the Z-scheme ZnIn2S4/MoO3 catalyst. Based on reactive species determination results, the Z-scheme charge transfer mechanism of ZnIn2S4/MoO3 was discussed and proposed. This study paves the way toward the development of highly efficient direct Z-scheme structures for a multitude of applications.

Colloidal Template Synthesis of Nanomaterials by Using Microporous Organic Nanoparticles: The Case of C@MoS2 Nanoadsorbents

The so-called colloidal template synthesis has been applied to the preparation of surface-engineered nanoadsorbents. Colloidal microporous organic network nanotemplates (C-MONs), which showed a high surface area (611 m²  g^-1 ) and enhanced microporosity, were prepared through the networking of organic building blocks in the presence of poly(vinylpyrrolidone) (PVP). Owing to entrapment of the PVP in networks, the C-MONs showed good colloidal dispersion in EtOH. MoS₂ precursors were incorporated into the C-MONs and heat treatment afforded core-shell-type C@MoS₂ nanoparticles with a diameter of 80 nm, a negative zeta potential (-39.5 mV), a high surface area (508 m²  g^-1 ), and excellent adsorption performance towards cationic dyes (q_max =343.6 and 421.9 mg g^-1 for methylene blue and rhodamine B, respectively).

Reversible Modulated Upconversion Luminescence of MoO3:Yb3+,Er3+ Thermochromic Phosphor for Switching Devices

Reversible modulation of upconversion luminescence induced by the external field stimuli exhibits potential applications in various fields, such as photoswitches, optical sensing, and optical memory devices. Herein, a new MoO₃:Yb³⁺,Er³⁺ thermochromic phosphor was synthesized via a high-temperature solid-state method, and the reversible color modification of the MoO₃:Yb³⁺,Er³⁺ phosphor was obtained by alternating the sintering conditions either in a reducing atmosphere or in air. The color of the MoO₃:Yb³⁺,Er³⁺ phosphor changed from light-yellow to blue under sintering in the reducing atmosphere and returned back after sintering again in air. The influence of reversible thermochromism on the upconversion luminescence of MoO₃:Yb³⁺,Er³⁺ phosphor was investigated. The MoO₃:Yb³⁺,Er³⁺ phosphor prepared in air exhibited visible upconversion luminescence, while the MoO₃:Yb³⁺,Er³⁺ phosphor has no upconversion luminescence after sintering in the reducing atmosphere. This up-conversion luminescence modulation shows excellent reproducibility after several cycles. The thermochromic MoO₃:Yb³⁺,Er³⁺ phosphor with reversible modulated upconversion luminescence shows great potential for practical applications in optical switches and optoelectronic multifunctional devices.

Rational inert-basal-plane activating design of ultrathin 1T' phase MoS2 with a MoO3 heterostructure for enhancing hydrogen evolution performances

Activating both the inert basal plane and edge sites of molybdenum-disulphide (MoS2) is a significant yet challenging step in boosting their performance for the hydrogen evolution reaction (HER). In this study, the density functional theory calculation results show that the incorporation of MoO3 fragments leads to a slight out-of-plane distortion of the 1T-MoS2 phase of the resultant O-Mo-S framework, giving rise to a 1T'-MoS2/MoO3 heterostructure, where gap states around the Fermi level allow hydrogen evolution over both its basal plane (Mo-site) and edges (S-sites). Under the guidance of density functional theory, conducted via an efficient one-step solvothermal route, ultrathin metallic-phase 1T'-MoS2/MoO3 heterojunction nanosheets with 3D hollow structures and a very small size (d = ∼120 nm) were precisely designed and constructed. The electrochemical measurements show that such a material possesses a low overpotential at 10 mA cm-2 (η10, 109 mV) and a Tafel slope (42 mV dec-1). In addition, the HMHSs also led to excellent H2 production up to 22.108 mmol g-1 h-1 and good durability under the photocatalytic process. To the best of our knowledge, the performance of this catalyst is better than that of most previously reported Mo-based non-noble catalysts for the HER. The excellent HER activity of this catalyst is highlighted by its unique synergistic effect between 1T'-MoS2 and MoO3 with an activated inert basal plane and fantastic hollow structure with a large surface area and high content of edge sites.

Two-Dimensional Transition Metal Oxide and Chalcogenide-Based Photocatalysts

Two-dimensional (2D) transition metal oxide and chalcogenide (TMO&C)-based photocatalysts have recently attracted significant attention for addressing the current worldwide challenges of energy shortage and environmental pollution. The ultrahigh surface area and unconventional physiochemical, electronic and optical properties of 2D TMO&Cs have been demonstrated to facilitate photocatalytic applications. This review provides a concise overview of properties, synthesis methods and applications of 2D TMO&C-based photocatalysts. Particular attention is paid on the emerging strategies to improve the abilities of light harvesting and photoinduced charge separation for enhancing photocatalytic performances, which include elemental doping, surface functionalization as well as heterojunctions with semiconducting and conductive materials. The future opportunities regarding the research pathways of 2D TMO&C-based photocatalysts are also presented.

Enhanced photocatalytic hydrogen evolution from in situ formation of few-layered MoS2/CdS nanosheet-based van der Waals heterostructures

Here we report for the first time that the H₂ bubbles generated by photocatalytic water splitting are effective in the layer-by-layer exfoliation of MoS₂ nanocrystals (NCs) into few layers. The as-obtained few layers can be in situ assembled with CdS nanosheets (NSs) into van der Waals heterostructures (vdWHs) of few-layered MoS₂/CdS NSs which, in turn, are effective in charge separation and transfer, leading to enhanced photocatalytic H₂ production activity. The few-layered MoS₂/CdS vdWHs exhibited a H₂ evolution rate of 140 mmol g_(CdS)^-1 h^-1 and achieved an apparent quantum yield of 66% at 420 nm.

Modification of Ag3VO4 with graphene-like MoS2 for enhanced visible-light photocatalytic property and stability

Graphene-like MoS₂/Ag₃VO₄ composites exhibited remarkably enhanced photocatalytic activities for the photodegradation of dyes within a short time compared to pure Ag₃VO₄.