Three dimensional (3D) nanostructured assembly of MoS₂-WS₂/Graphene as high performance electrocatalysts

A promising electrocatalyst material composed of 2D layered MoS₂-WS₂ heterostructure hierarchically assembled into a 3D highly interconnected macroporous network of graphene was facilely fabricated. This in-situ synthesis method involves hydrothermal reaction followed by moderate thermal annealing which guarantees the uniform distribution of the MoS₂-WS₂ heterojunctions within graphene matrix. The presence of 3D conductive and porous graphene network and the combined merits of MoS₂ and WS₂ endow the resulting 3D MoS₂-WS₂/graphene nanohybrids with unique conductivity pathways and channels for electrons and with outstanding electrocatalytic performance towards enhanced hydrogen evolution reaction (HER). This 3D nanohybrid delivered the small overpotential of 110 mV, and the small Tafel slope of 41 mV per dec, demonstrating high HER activity. Furthermore, the resulting nanohybrids exhibit excellent stability as very trivial drop in the current density was noticed even after 2000 cycles. The superior electrocatalytic performance of 3D MoS₂-WS₂/graphene over other non-precious metal electrocatalysts is accredited to the robust synergism of 2D MoS₂-WS₂ with 3D graphene that offer ample active sites and improved conductivity for HER. The proposed approach can be further extended to modify other layered transition metal dichalcogenides with hierarchical 3D porous structure as a competent electrocatalysts for HER.