MoS2 nanosheets decorated with ultrafine Co3O4 nanoparticles for high-performance electrochemical capacitors

Nanocomposites can be fabricated in such a way that they retain the advantages but overcome the limitations of each single-material component. Here, we report a convenient route to fabricate MoS2-Co3O4 composites via laser ablation in liquids (LAL) and aging-induced phase transformation. The reactive Co colloids obtained through LAL are used as a non-ion precursor to anchor Co3O4 nanoparticles (NPs) onto the surfaces of MoS2 nanosheets without using any stabilizers. In the fabricated composites, the MoS2 nanosheets serve as a flexible conducting substrate for the in situ phase transformation and crystalline growth of Co3O4 NPs and the network structure of the sheets prevents NPs from further aggregation. Co3O4 NPs not only function as a high-rate capability electrode material but also stabilize the composite structure, thereby generating accessible active surfaces on the MoS2 nanosheets for electrolyte penetration during charging/discharging. The structure and morphology of the as-constructed composites are investigated through scanning and transmission electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. As an active hybrid supercapacitor electrode material, the active composite materials exhibit higher electrochemical performance than either pure MoS2 or pure Co3O4. The superior performance can be attributed to the synergistic effects of the pseudocapacitive reactions from the MoS2 nanosheets and the Faradaic battery reactions of the anchored ultrafine Co3O4 NPs.