Separable magnetic MoS2@Fe3O4 nanocomposites with multi-exposed active edge facets toward enhanced adsorption and catalytic activities

We synthesized fluffy MoS2 material stacked by ultrathin nanosheets through adjusting different mass ratios of starting materials via a facile hydrothermal method. Surprisingly, XRD characterization results demonstrated that the intensity ratio of (100) to (002) of ultrathin MoS2 nanosheets was 0.90 with a 4:5 (CH3CSNH2: Na2MoO4·2H2O) mass ratio (M4-5). To the best of our knowledge, this value should be high, implying that the obtained MoS2 nanosheets exposed considerable (100) facets. Because the noncentrosymmetric Mo-2S on edges terminated by dangling bonds exhibits rich defects, high active MoS2 edge planes (100) prevail over inert MoS2 basal planes (002). To overcome its easy suspension and difficult recovery, the magnetic Fe3O4 was selected for in situ doping with ultrathin M4-5, and a unique structure of stable MoS2@Fe3O4 (M@F) nanocomposites-like randomly stacked rose petals-wrapped spherical chocolate beans was obtained for the first time. The introduction of Fe3O4 has to sacrifice some edge active sites, but after balancing the magnetic and active sites, (100)/(002) of MoS2 in M@F can also reach 0.56, showing that edges of MoS2 nanosheets are still multi-exposed. Abundant exposed edges of M@F provide numerous active centers, so M@F nanocomposites exhibited excellent performance for both the 4-nitrophenol (4-NP) reduction and dye adsorption. Therefore, it has great application prospects in wastewater treatment and reduction reaction and is also worth exploring in other applications.