High Phase‐Purity 1T‐MoS 2 Ultrathin Nanosheets by a Spatially Confined Template

Effect of fluorine doping on the NO2-sensing properties of MoS2nanoflowers

The somewhat slow recovery kinetics of NO2sensing at low temperatures are still challenging to overcome. To enhance the gas sensing property, fluorine is doped to MoS2nanoflowers by facile hydrothermal method. Extensive characterization data demonstrate that F was effectively incorporated into the MoS2nanoflowers, and that the microstructure of the MoS2nanoflowers did not change upon F doping. The two MoS2doped with varying concentrations of fluorine were tested for their sensing property to NO2gas. Both of them show good repeatability and stability. A smaller recovery time was seen in the F-MoS2-1 sample with a little amount of F loading, which was three times quicker than that of pure MoS2. The key reason for the quicker recovery time of this material was found to be the fluorine ions that had been adsorbed on the surface of F-MoS2-1 would take up some of the NO2adsorption site. Additionally, the sample F-MoS2-2 with a higher F doping level demonstrated increased sensitivity. The F-MoS2-2 sensor's high sensitivity was mostly due to the lattice fluorine filled to the sulfur vacancy, which generated impurity levels and reduced the energy required for its electronic transition. This study might contribute to the development of new molybdenum sulfide based gas sensor.

1T/2H Mixed Phase MoS2 Nanosheets Integrated by a 3D Nitrogen-Doped Graphene Derivative for Enhanced Electrocatalytic Hydrogen Evolution

Molybdenum disulfide (MoS₂) has become one of the most promising non-platinum-based electrocatalysts for the hydrogen evolution reaction (HER) because of its unique layered structure. However, the catalytic performance of the thermodynamically stable MoS₂ is hindered by its poor conductivity and scarce active sites. We developed a 3D porous N-doped graphene derivative-integrated metal-semiconductor (1T-2H) mixed phase MoS₂ (MNG) using urea as a doping reagent. The highly exposed active sites were achieved by inducing the phase transition of MoS₂ from 2H phase to 1T phase and the inclusion of highly N-incorporated reduced graphene oxide, both of which were simultaneously realized by optimizing the concentration of the doping reagent. Moreover, the charge/proton transfer was enhanced by the well-designed porous architecture and hydrophilic 1T-MoS₂. With these advantages, the optimized MNG-40 catalyst has a small overpotential of 157 mV at a cathodic current density of 10 mA cm^-2, a relatively low Tafel slope of 45.8 mV dec^-1, and an excellent stability. This work represents a new strategy to design higher-performance HER catalysts and provides new insights into the structural regulation of metal composite transitions.

Nanoconfined Water-Molecule Channels for High-Yield Solar Vapor Generation under Weaker Sunlight

Solar vapor generation is a promising method to efficiently produce fresh water. However, the insufficient vapor yields under natural daylight restrict its practical applications, and the basic evaporation mechanisms are deficient for reasonable design of evaporator structure. Here, hydrophobic nano-confined water molecule channels (NCWMCs) are demonstrated, which can reduce the vaporization enthalpy for water evaporation and achieve a record vapor generation rate of 1.25 kg m^-2 h^-1 under 0.5 sun irradiation. Molecular dynamics simulations reveal the cluster-evaporation process in the NCWMC system. As a result, the evaporator with NCWMC system can effectively purify seawater and wastewater samples using this environmentally friendly strategy.