Amorphous MoS x O y / h -BN x O y Nanohybrids: Synthesis and Dye Photodegradation.

Molybdenum sulfide is a very promising catalyst for the photodegradation of organic pollutants in water. Its photocatalytic activity arises from unsaturated sulfur bonds, and it increases with the introduction of structural defects and/or oxygen substitutions. Amorphous molybdenum sulfide ( a -MoS x O y ) with oxygen substitutions has many active sites, which create favorable conditions for enhanced catalytic activity. Here we present a new approach to the synthesis of a -MoS x O y and demonstrate its high activity in the photodegradation of the dye methylene blue (MB). The MoS x O y was deposited on hexagonal boron oxynitride ( h -BNO) nanoflakes by reacting h -BNO, MoCl 5 , and H 2 S in dimethylformamide (DMF) at 250 °C. Both X-ray diffraction analysis and high-resolution TEM show the absence of crystalline order in a -MoS x O y . Based on the results of Raman and X-ray photoelectron spectroscopy, as well as analysis by the density functional theory (DFT) method, a chain structure of a -MoS x O y was proposed, consisting of MoS 3 clusters with partial substitution of sulfur by oxygen. When a third of the sulfur atoms are replaced with oxygen, the band gap of a -MoS x O y is approximately 1.36 eV, and the valence and conduction bands are 0.74 eV and -0.62 eV, respectively (relative to a standard hydrogen electrode), which satisfies the conditions of photoinduced splitting of water. When illuminated with a mercury lamp, a -MoS x O y / h -BN x O y nanohybrids have a specific mass activity in MB photodegradation of approximately 5.51 mmol g -1 h -1 , which is at least four times higher than so far reported values for nonmetal catalysts. The photocatalyst has been shown to be very stable and can be reused.