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.