Silicon nanowires (SiNWs) are widely used as photocathodes because of their large electrochemically available surface-area density and inherent ability to decouple light absorption from the transport of minority carriers. In order to minimize overpotential for solar-driven hydrogen (H) production, a combination of an ultrathin molybdenum disulfide (MoS) layer with SiNWs as photocathode has attracted much attention. Herein, for the first time, this study presents the synthesis of a composite photocathode via direct growth of ultrathin MoS nanosheets on SiNWs (referred to as SiNWs/MoS) by one-step chemical vapor deposition (CVD). Due to the high surface-area density of the arrays of SiNWs, the discontinuous MoS nanosheets grown on the SiNWs achieved a much higher density of active sites. Moreover, the coating of MoS on the SiNWs was found to protect the photocathode during the photoelectrochemical (PEC) reaction. A high efficiency with photocurrent j of 16.5 mA cm (at 0 V vs. reversible hydrogen electrode) and an excellent stability over 48 h of PEC operation were achieved under a simulated 1 sun irradiation.

Water disinfection is of great importance for human health and daily life. Photocatalysts with high efficiency, environmental protection, and narrow bandgaps are critical for practical water treatment. Here, a general approach is reported for the direct growth of pyramid-type MoS (pyramid MoS) on transparent glass by chemical vapor deposition (CVD). The pyramid MoS exhibits a smaller bandgap and higher bactericidal activity than most TiO-based photocatalysts. The adjustable-bandgap nature of two-dimensional (2-D) MoS can harvest a wide spectrum of sunlight and provide more active sites with which to generate reactive oxygen species (ROS) for bacterial death in water. Furthermore, silver (Ag) with several nanometers thicknesses is thermally evaporated on the pyramid MoS, which can greatly facilitate electron-hole pair separation to generate more ROS and has a certain bactericidal effect. With our established approach, under simulated visible light, more than 99.99% of Escherichia coli can be successfully deactivated in 40 min, with an effective mass per unit of less than 0.7 mg L in a 0.9 wt % NaCl solution. Besides, for the first time, the generation of ROS is confirmed with in situ Raman spectroscopy on pyramid MoS@Ag glass, and the related bactericidal mechanism is present as well.

Nanostructured molybdenum disulfide (MoS) has been considered as one of the most promising catalysts in the hydrogen evolution reaction (HER), for its approximately intermediate hydrogen binding free energy to noble metals and much lower cost. The catalytically active sites of MoS are along the edges, whereas thermodynamically MoS favors the presence of a two-dimensional (2-D) basal plane and the catalytically active atoms only constitute a small portion of the material. The lack of catalytically active sites and low catalytic efficiency impede its massive application. To address the issue, we have activated the basal plane of monolayer 2H MoS through an ultrathin alumina mask (UTAM)-assisted nanopore arrays patterning, creating a high edge density. The introduced catalytically active sites are identified by Cu electrochemical deposition, and the hydrogen generation properties are assessed in detail. We demonstrate a remarkably improved HER performance as well as the identical catalysis of the artificial edges and the pristine metallic edges of monolayer MoS. Such a porous monolayer nanostructure can achieve a much higher edge atom ratio than the pristine monolayer MoS flakes, which can lead to a much improved catalytic efficiency. This controllable edge engineering can also be extended to the basal plane modifications of other 2-D materials, for improving their edge-related properties.

COMMUNICATION 1801663 (1 of 7)

The intrinsic magnetism of MoS2 has been extensively investigated via simulations, but few reliable experimental results have been explored. Herein, we develop zigzag-edge rich layered structural MoS2 pyramids via chemical vapor deposition, triggering exceptional ferromagnetism. The magnetic measurements revealed the robust ferromagnetism of MoS2 pyramids compared with MoS2 flakes. The existence of ferromagnetism was mostly attributed to the presence of abundant zigzag-edges in the layered pyramids, confirmed by transmission electron microscopy, vibrating sample magnetometry, and magnetic force microscopy. Moreover, a clearly identified remnant and switchable magnetic moment was revealed for the first time in the MoS2 pyramid. This study provides sound evidence with the zigzag-edge induced ferromagnetism of the MoS2 materials, promising potential magnetic and spintronic applications.

Photocatalysis is one of the most promising technologies in wastewater treatment. However, the inactivity to visible light and the inconvenience to recycle severely limit its practical application. In this work, via a facile hydrothermal method, Fe3O4 NPs were integrated onto the surfaces of 3D ball-flower-like MoS2 microspheres as efficiently visible light responsive and magnetically recyclable photocatalysts. Experimental results indicate that, an optimal loading amount (20 wt %) of Fe3O4 NPs can not only effectively enhance the photocatalytic ability of the MoS2/Fe3O4 (MF) hybrid composite with approximately 2 times better than pure MoS2, but also make it conveniently recycle from water by an external magnetic field. The photoelectrochemical studies also reveal that the incorporation of Fe3O4 NPs can effectively enhance the charge transfer rate and accelerate separation of photoinduced charge carriers. The surface catalytic mechanism of MF hybrid composite was also explored through XPS spectra. With both the excellent photocatalytic performance and magnetical recyclability, the 20 wt %-MF hybrid composite is considered to be a promising and competitive photocatalyst for wastewater treatment utilizing solar energy.

Due to the thickness-independent vertical conductivity and high density of active edge sites, MoS2 pyramids demonstrate a highly enhanced HER performance compared to that of MoS2 triangular flakes.

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