Abstract:

Amorphous materials have recently gained much attention as electrode materials in supercapacitor application due to the presence of larger amount active sites which can efficiently increase the storage capacity of the materials. Nano engineering is an elegant approach to fully utilize the advantages of the amorphous structure. Moreover, large surface area and high conductivity of reduced graphene oxide (RGO) can efficiently increase the storage capacity of the system. Exploiting this idea, in the present work, we have successfully synthesized amorphous MoS₂ of two different sizes on reduced graphene oxide and thoroughly investigated the supercapacitor behavior of the system. The specific capacitance of the composite structures has been found to be largely increased with decreasing size of the amorphous nano particle. The specific capacitance of amorphous MoS₂-RGO composite containing nearly 50 nm of MoS₂ found to be 270 F/g whereas when the particle size is reduced to 5-7 nm, value of specific capacitance increases to 460 F/g. The large increase in specific capacitance with the tuning of the size of amorphous nano particle has been explained by the presence of a large number of active sulfur edges of ultra-small MoS₂ nano structure along with the better charge transport which can effectively increase the storage capacity of the overall system. The retention in the capacitance of the material has been found to be 90 % after 5000 cycles.

Key words: Supercapacitor, Ultrasmall amorphous MoS₂ nanoparticles, Sulfur edge sites, Reduced graphene oxide (RGO), Specific capacitance