Adsorption behavior of thiophene on MoS2 under a microwave electric field via DFT and MD studies

Surface structural probing and photoelectrochemical characterization of electrodeposited MoS2 nanostructured thin film

Molybdenum disulfide (MoS2) has advantageous traits and characteristics that make it suitable for a diverse array of practical applications, such as optoelectronics and gas sensing. Enhancing the surface area of the adsorbent leads to a proportional increase in its performance. Hence, the synthesized two-electrode electrodeposited MoS2 (ED-MoS2) thin films were microstructurally characterized to investigate its surface modulation for suitable enhancement in its applicative properties. The characterization shows that the surface properties of the deposited film can easily be modulated to favor its needs and can be done by simply varying its electrodeposition parameters, such as growth period and voltage supplied. In addition, persistent n-type conductivity of intrinsic MoS2 makes it challenging to achieve p-type conductivity. By simply varying the cathodic potential, the challenge of obtaining p-type MoS2 thin films was solved. The photoelectrochemical cell measurements revealed that lower cathodic potentials (1.15-1.35 V) favored the growth of p-type MoS2 layers while the growth of n-type MoS layers was achieved at the higher cathodic potential.

Dissipative Particle Dynamics Using Conductor-Like Screening Model for Real Solvents-Based Interaction Parameters for Classical Simulations of Dibenzothiophene Adsorption on Molybdenum Disulfide Nanoparticles

The previous step before the catalytic activity of MoS2 nanoparticles for the hydrodesulfurization of dibenzothiophene (DBT), i.e., the DBT adsorption, is studied through dissipative-particle-dynamics (DPD) simulations. Density-functional-theory (DFT) calculations reveal that although DBT is chemisorbed, and, therefore, there is an intermolecular electronic exchange leading to the weakening of the DBT's C-S bonds, the formed individual linking bonds among DBT and MoS2 are noncovalent, fact that allows the application of DPD in order to at least qualitatively estimate the fraction of the content of DBT molecules within an oleic solvent that can be adsorbed by the MoS2 nanoparticles. With the sake of getting realistic insights, we calculated the classical-DPD interaction parameters through the quantum-statistical approach conductor-like screening model for real solvents. A comparison between DFT calculations and the DPD simulations reveals that the quantum spontaneous attraction of DBT by MoS2 nanoparticles begins at the distance where the DBT's volumetric density in the neighborhood of a MoS2 nanoparticle is maximum, as well as that the alkylic chain of the oleic solvent has an important influence on the performance of the catalyst since the chain length increases the probability that DBT will find MoS2. These results suggest the combined DFT and DPD study can be useful for the design of HDS catalysts.

Enhanced Uranium Extraction via Charge Dynamics and Interfacial Polarization in MoS2/GO Heterojunction Electrodes

The removal of uranyl ions (UO2 2+) from water is challenging due to their chemical stability, low concentrations, complex water matrix, and technical limitations in extraction and separation. Herein, a novel molybdenum disulfide/graphene oxide heterojunction (MoS2/GO-H) is developed, serving as an effective electrode for capacitive deionization (CDI). By combining the inherent advantages of electroadsorption and electrocatalysis, an innovative electroadsorption-electrocatalysis system (EES) strategy is introduced. This system utilizes interface polarization at the MoS2 and GO interface, creating an additional electric field that significantly influences carrier behavior. The MoS2/GO-H electrode, with its extraordinary adsorption capacity of 805.57 mg g-1 under optimal conditions, effectively treated uranium-laden wastewater from a mine, achieving over 90% removal efficiency despite the presence of numerous competing ions at concentrations significantly higher than UO2 2+. Employing density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations, it is found that the MoS2/GO-H total charge density at the Fermi level, enhanced by interfacial polarization, surpasses that of separate MoS2 and GO, markedly boosting conductivity and electrocatalytic effectiveness.

Influence of Inorganic Anions on the Chemical Stability of Molybdenum Disulfide Nanosheets in the Aqueous Environment

Chemical stability is closely associated with the transformations and bioavailabilities of engineered nanomaterials and is a key factor that governs broader and long-term application. With the growing utilization of molybdenum disulfide (MoS2) nanosheets in water treatment and purification processes, it is crucial to evaluate the stability of MoS2 nanosheets in aquatic environments. Nonetheless, the effects of anionic species on MoS2 remain largely unexplored. Herein, the stability of chemically exfoliated MoS2 nanosheets (ceMoS2) was assessed in the presence of inorganic anions. The results showed that the chemical stability of ceMoS2 was regulated by the nucleophilicities and the resultant charging effects of the anions in aquatic systems. The anions promote the dissolution of ceMoS2 by triggering a shift in the chemical potential of the ceMoS2 surface as a function of the anion nucleophilicity (i.e., charging effect). Fast charging with HCO3- and HPO42-/H2PO4- was validated by a phase transition from 1T to 2H and the emergence of MoV, and it promoted oxidative dissolution of the ceMoS2. Additionally, under sunlight, ceMoS2 dissolution was accelerated by NO3-. These findings provide insight into the ion-induced fate of ceMoS2 and the durability and risks of MoS2 nanosheets in environmental applications.

Recovering valuable metals from spent hydrodesulfurization catalyst via blank roasting and alkaline leaching

Spent hydrodesulfurization (HDS) catalysts, containing considerable amount of pollutants and metals including vanadium (V), molybdenum (Mo), aluminum (Al), and nickel (Ni), are considered as hazardous wastes which will result in not only ecosystem damage but also squandering resource. Herein, a process featuring blank roasting-alkaline leaching is proposed to recover spent HDS catalyst. During roasting, low-valence compounds convert to high-valence oxides which can be leached out by NaOH solution. Afterwards, leaching solution is subjected to crystallization to separate metals. The results show that for samples roasted at 650 °C, 97% V, 96% Mo, and 88% Al are leached out at optimal condition; for samples roasted at 1000 °C, selective leaching of 91% V and 96% Mo respectively, are realized, with negligible Al being dissolved. NiO is insoluble in strong alkali leaving in residue. The advantages of this process are that first, the leaching of V, Mo, and Al can be manipulated by controlling roasting conditions, providing flexible process design. Second, leaching solution can be fully recycled. Finally, mild leaching condition and clean separation of V, Mo, and Al is achieved, proving fundamental information for peer researches to facilitate their future research on the development of more efficient and cleaner technologies.

Study of the microscopic mechanism of lauryl glucoside wetting coal dust: Environmental pollution prevention and control

Molecular dynamics simulation combined with experimental methods were used to investigate the adsorption and wetting process of 25 lauryl glucoside (APG-12) molecules on coal molecules and in turn study the dust suppression mechanism by APG-12 at the molecular level. Through wetting experiments, our preliminary findings showed that APG-12 does have a certain wetting effect on coal dust. According to density functional theory in molecular dynamics simulations, the electrostatic potential and surface charge of the APG-12 and coal molecular models were analyzed to identify their nucleophilic and electrophilic regions, and illustrate the hydrogen bond adsorption mechanism. The dynamics simulation results showed that APG-12 molecules can be easily adsorbed on the surface of coal molecules and then adsorb water molecules around them under the action of hydrogen bonds. This was consistent with the results of an analysis of the system's radial distribution function and the relative concentration distribution of each component in the Z-axis direction. The results are in good agreement with the experimental results from scanning electron microscopy and energy dispersive spectrometer analysis. These data provide further evidence that APG-12 can clearly improve the wettability and suppression of coal dust, which is of great importance for controlling coal dust pollution.

The Role of Nanodispersed Catalysts in Microwave Application during the Development of Unconventional Hydrocarbon Reserves: A Review of Potential Applications

Electromagnetic impact on oil reservoir manifests itself in various physical and chemical phenomena and attracts a significant scientific and technological interest. Microwave (MW) radiation heating can be more efficient for the oil recovery than heat transfer by convection or by thermal conduction. MW influence can also lead to significant changes in the physicochemical and rheological properties of oil caused by chemical processes of transformation of the oil high-molecular components such as resins and asphaltenes. The efficiency of transition-metal catalysts applied for the in-situ conversion of hydrocarbons directly in the reservoir might be significantly increased by exposing the oil formation to MW radiation. Actually, transition metals nanoparticles and their oxides are considered as active absorbers of MW radiation and; therefore, they can be used to intensify MW impact on the reservoir. Catalyst particles dispersed in the formation provide enhanced MW sweep. Taken together, the functioning of the catalysts and the effect of microwave radiation provide deep conversion of resins and asphaltenes, a decrease in the viscosity of the produced oil and an increase in oil recovery factor, along with a decrease in water cut of the well production. The present review analyzes the latest works on the combined application of microwave exposure and dispersed catalysts. In addition, this review discusses the prospects and perspectives of practical application of electromagnetic heating to enhance heavy oil recovery in the presence of nanoparticles.

Synthesis of a BiPO4/Bi4O5I2 heterostructure for efficient degradation of oil field pollutants

In this research, composite photocatalysts were found to have a superior photocatalytic performance.