Activation of the MoS2 Basal Plane to Enhance CO Hydrogenation to Methane Activity Through Increasing S Vacancies

Effect of DBD Plasma Treatment on Activity of Mo-Based Sulfur-Resistant Methanation Catalyst

By combining the advantages of dielectric barrier discharge (DBD) low temperature plasma and fluidized bed, the effect of plasma on the performance of supported Mo-based catalyst was studied in this paper. The performance of the catalyst obtained by plasma treatment, calcined, plasma+calcined was compared, and the appropriate catalyst preparation scheme was explored. Comparing with the three catalysts, it was concluded that the catalyst average conversion after 30 W plasma treatment is 33.40 %, which was 8.94 % and 12.75 % higher than the other two, respectively. The structure and properties of the catalyst were characterized by N2-Physisorption, H2-chemisorption, XRD, TEM, XPS, Raman and NO-pulse adsorption. Then, by analyzing the characterization results, it can be seen that plasma can make the catalyst have a higher specific surface area and a more dispersed active metal with smaller grain size. Through the surface species identification characterization, it was found that plasma can produce more defective structures and expose more active sites, which is the main reason for the difference in conversion.

Nitrogen activation and surface charge regulation for enhancing the visible-light-driven N2 fixation over MoS2/UiO-66(SH)2

A series of dehydrated MoS2/UiO-66(SH)2 (MS/UiS) composites has been prepared as photocatalysts for N2 fixation. Typically, 10% MS/UiS exhibits the best performance with an NH4+ yield rate of 54.08 μmol∙g-1∙h-1. 15N isotope test confirmed that the sample 10% MS/UiS was most effective for reducing N2 to ammonia. Such enhanced activity was due to the presence of abundant unsaturated Zr and Mo sites which would synergistically promote the adsorption and activation of N2. The photogenerated electrons would transfer to the unsaturated Zr-O clusters while part of photogenerated electrons at the interface migrate to MS via MoVI-O interactions between MS and UiS. These two electron transfer pathways effectively promote the separation of photogenerated carriers. The activated N2 is reduced to ammonia by the synergistic effect of protonated hydrogen and photogenerated electrons. Finally, a possible N2 fixation mechanism is proposed which emphasizes the significant roles of nitrogen activation and interface interaction in composites photocatalyst for improving photocatalytic performance.

Study on the Performance of Ni-MoS2 Catalysts with Different MoS2 Structures for Dibenzothiophene Hydrodesulfurization

Hydrodesulfurization (HDS) is an important process for the production of clean fuel oil, and the development of a new environmentally friendly, low-cost sulfided catalyst is key research in hydrogenation technology. Herein, commercial bulk MoS2 and NiCO3·2NiOH2·4H2O were first hydrothermally treated and then calcined in a H2 or N2 atmosphere to obtain Ni-MoS2 HDS catalysts with different structures. Mechanisms of hydrothermal treatment and calcination on Ni-MoS2 catalyst structures were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS). The catalytic performance of Ni-MoS2 catalysts was evaluated by the HDS reaction of dibenzothiophene (DBT) on a fixed bed reactor, and the structure-activity relationship between the structures of the Ni-MoS2 catalyst and the HDS of DBT was discussed. The results showed that the lateral size, the number of stacked layers, and the S/Mo atomic ratio of MoS2 in the catalyst decreased and then increased with the increase of the hydrothermal treatment temperature, reaching the minimum at the hydrothermal treatment temperature of 150 °C, i.e., the lateral size of MoS2 in the catalyst was 20-36 nm, the number of stacked layers of MoS2 was 5.4, and the S/Mo ratio in the catalyst was 1.80. In addition, the effects of different calcination temperatures and calcination atmospheres on the catalyst structures were investigated at the optimum hydrothermal treatment temperature. The Ni-Mo-S and NixSy ratios of the catalysts increased and then decreased with the increasing calcination temperature under a H2 atmosphere, reaching a maximum at a calcination temperature of 400 °C. Therefore, DBT exhibited the best HDS activity over the H-NiMo-150-400 catalyst, and the desulfurization rate of DBT reached 94.7% at a reaction temperature of 320 °C.

Coupled Co-Doped MoS2 and CoS2 as the Dual-Active Site Catalyst for Chemoselective Hydrogenation

Catalytic hydrogenation plays an important role in the industrial production of fine chemicals. Herein, we report a Co-doped MoS₂ and CoS₂ composite with a coupling interface and successfully apply it for the chemoselective hydrogenation of p-chloronitrobenzene to p-chloroaniline. The target catalyst 0.5CoMoS has ∼100% conversion and ∼100% selectivity. Experiments and theoretical calculations reveal that CoS₂ is more favorable for adsorbing and activating H₂ and provides active hydrogen (H_a) to Co-doped MoS₂ by the coupling interface. By matching the production and consumption rates of H_a, the maximization of the reaction yield was achieved. This work may promote the study of MoS₂-based catalysts for chemoselective hydrogenation.

Experimental Realization and Computational Investigations of B2S2 as a New 2D Material with Potential Applications

A new two-dimensional material B₂S₂ has been successfully synthesized for the first time and validated using first-principles calculations, with fundamental properties analyzed in detail. B₂S₂ has a similar structure as transition-metal dichalcogenides (TMDs) such as MoS₂, and the experimentally prepared free-standing B₂S₂ nanosheets show a uniform height profile lower than 1 nm. A thickness-modulated and unique oxidation-level dependent band gap of B₂S₂ is revealed by theoretical calculations, and vibration signatures are determined to offer a practical scheme for the characterization of B₂S₂. It is shown that the functionalized B₂S₂ is able to provide favorable sites for lithium adsorption with low diffusion barriers, and the prepared B₂S₂ shows a wide band photoluminescence response. These findings offer a feasible new and lighter member for the TMD-like 2D material family with potential for various aspects of applications, such as an anode material for Li-ion batteries and electronic and optoelectronic devices.