[Mo3S13]2– clusters have become known as one of the most efficient catalysts for the hydrogen evolution reaction (HER) because most of the sulfur (S) atoms in the cluster are exposed, resulting in many active sites. However, the origin of the cluster formation and active S sites in the cluster is unknown, hindering the development of efficient catalysts. Herein, the mechanism of the transition from amorphous MoS3 to [Mo3S13]2– clusters is systematically investigated. In addition, the active S sites have been identified by the selective removal of S atoms via low-temperature heat treatment. In summary, we believe that the clusters grow from amorphous MoS3 with apical S atoms, and bridging S atoms are the active HER sites in the [Mo3S13]2– clusters. The clusters deposited on carbon nanotubes exhibited good electrochemical HER activity with a low onset potential of −96 mV, a Tafel slope of 40 mV/decade, and stability for 1000 cycles.

A facile and efficient synthesis of a solution‐processable MoO3/MoS2 featuring uniformly decorated MoO3 nanoparticles onto exfoliated MoS2 nanosheets is realized via a one‐step oxidation and spontaneous exfoliation method using hydrogen peroxide. By using MoO3/MoS2 as a hole extraction layer in organic solar cells, high efficiencies, regardless of annealing conditions of the interfacial layer, and excellent long‐term stability are demonstrated.

The drying process of graphene-polymer composites fabricated by solution-processing for excellent dispersion is time consuming and suffers from a restacking problem. Here, we have developed an innovative method to fabricate polymer composites with well dispersed graphene particles in the matrix resin by using solvent free powder mixing and in-situ polymerization of a low viscosity oligomer resin. We also prepared composites filled with up to 20 wt% of graphene particles by the solvent free process while maintaining a high degree of dispersion. The electrical conductivity of the composite, one of the most significant properties affected by the dispersion, was consistent with the theoretically obtained effective electrical conductivity based on the mean field micromechanical analysis with the Mori-Tanaka model assuming ideal dispersion. It can be confirmed by looking at the statistical results of the filler-to-filler distance obtained from the digital processing of the fracture surface images that the various oxygenated functional groups of graphene oxide can help improve the dispersion of the filler and that the introduction of large phenyl groups to the graphene basal plane has a positive effect on the dispersion.

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