Facile hydrothermal synthesis of MoS2 nano-sheets with controllable structures and enhanced catalytic performance for anthracene hydrogenation

Abstract

MoS₂ nano-sheets with controllable structures were prepared using a hydrothermal method. Effects of crystallization time, temperature and pH of the precursor solution on the structures, components and morphologies of MoS₂ nano-sheets were investigated. MoS₂ nano-sheets were characterized using XRD, Raman, elemental analysis, TG/DTG, SEM, and HRTEM. The characterization results show that intercalated MoS₂, intermediate MoS₂ with intercalated and semi-crystallized structures, and well crystallized hexagonal MoS₂ (denoted as 2H-MoS₂) were prepared by varying crystallization conditions, especially crystallization time. Intercalated MoS₂ possesses rich active sites and poor crystallinity. 2H-MoS₂ demonstrates high crystallinity but few active sites. As a transition structure during the crystallization process from intercalated MoS₂ to 2H-MoS₂, intermediate MoS₂ simultaneously possesses rich active sites and good crystallinity. The possible growth mechanism of MoS₂ nano-sheets in the hydrothermal process was proposed. The catalytic activities of MoS₂ nano-sheets with various structures were evaluated by anthracene hydrogenation. The evaluation results show that intermediate MoS₂ exhibits optimized catalytic activities of anthracene hydrogenation, which can be ascribed to the abundant active sites and desired stability of intermediate MoS₂. This work may provide theoretic guidance for creating active sites and tuning catalyst structure for the controllable synthesis of layered transition metal sulfides with high catalytic activities.