Morphological Effect of Graphene Nanosheets on Ultrathin CoS Nanosheets and Their Applications for High-Performance Li-Ion Batteries and Photocatalysis

A unique CoS-graphene sheet-on-sheet nanocomposite has been successfully prepared by anchoring CoS nanosheets on the surface of graphene nanosheets (GNS) with the assistance of the structure-directing agent of ethylenediamine. The shape and size of the introduced CoS nanosheets can be further adjusted by varying the amount of GNS. The unprecedented sheet-like CoS structure is believed to be matched well with GNS basically due to their similar two-dimensional structure with maximum contact areas between two components. The strong interaction between CoS and the underlying highly conductive graphene can facilitate fast electron and ion transport and improve structure stability of the composite. The composite with 26.2% GNS displays excellent electrochemical performance when evaluated as an anode for rechargeable lithium-ion battery. A larger-than-theoretical reversible capacity of 898 mAh/g can be delivered after 80 cycles at 0.1 C along with excellent high-rate cycling performance. The CoS-graphene sheet-on-sheet composite is also used for the first time as a photocatalyst with promising properties for the degradation of methylene blue.