Layer-Controlled Synthesis of MoS₂ by Thermal Decomposition of Alkylammonium Thiomolybdates for 4-Methylphenol...

Layer-controlled synthesis of MoS₂ is of great importance to understanding the structure-performance relation in the hydrodeoxygenation (HDO) reaction. However, the traditional chemical exfoliation method suffers from the disadvantages of a low yield and complex operation. Herein, we report a simple strategy to achieve layer-controllable synthesis of MoS₂ by thermal decomposition of alkylammonium thiomolybdates. Through increasing the length of the alkyl chain, the layer number of MoS₂ is tuned from multilayer to monolayer due to the obstruction effect of amorphous carbon in the growth process. Adopting 4-methylphenol (4-MP) as a probe molecule, it is found that the intrinsic HDO activity and direct deoxygenation (DDO) selectivity are enhanced with the decrease of the stacking number of MoS₂ catalysts. Consequently, the monolayer MoS₂-Bu prepared by thermal decomposition of tetrabutylammonium thiomolybdate shows the highest 4-MP conversion and toluene selectivity. By further doping Co promoters to form Co-Mo-S active phase, the Co/MoS₂-Bu catalyst achieved 99.6% 4-MP conversion and 99.3% toluene selectivity at 220 °C and 3.0 MPa for steady running of 48 h. The excellent stability is attributed to the isolation and hydrophobic effect of carbon species, which prevent the monolayer MoS₂ particles from sintering and surface oxidation.