Carbothermal-reduction-assisted CVD synthesis of layered MoS2 nanosheets on activated carbon support: Implication for photocatalysis

Abstract

The photocatalytic activity of MoS2-based heterostructures largely depends on the thickness and orientation of the MoS2 components. We report a new facile two-step carbothermal-reduction-assisted CVD synthesis protocol to produce horizontally and vertically aligned MoS2 nanosheets (NSs) on activated carbon (AC) granules. MoO3/AC pellets were first prepared by sonicating MoO3 and AC powders and then used as a substrate and Mo source to obtain MoS2/AC composites. A feature of the process is that MoO3 particles, prior to interaction with sulfur, undergo carbothermal reduction with the formation of Mo suboxides favorable for MoS2 growth. The thickness and orientation of MoS2 NSs strongly depend on the synthesis temperature. At 600 °C, horizontally oriented triangular MoS2 NSs are formed on the surface of molybdenum oxide particles, and at 700 °C, thin vertically oriented MoS2 NSs with a high aspect ratio (with a thickness and a lateral size of 20 × 5000 nm2) are grown. The high photocatalytic activity of MoS2/AC composites during the decompositions of organic dyes under UV radiation is associated with the thickness and orientation of MoS2 NSs. The vertical arrangement of the active edges intensifies the chemical interaction with the reagents, and the small NS thickness prevents the recombination of charge carriers and facilitates their transfer to the surface. The obtained results open up new possibilities for the development of cost-effective and scalable MoS2-based photocatalysts with tunable thickness and orientation of MoS2 NSs on commercially available AC substrates using a carbothermal-reduction-assisted CVD approach.