MoS2-coated vertical graphene nanosheet for high-performance rechargeable lithium-ion batteries and hydrogen production

Hybrid nanostructures composed of vertical graphene nanosheet (VGNS) and MoS2 nano-leaves are synthesized by the chemical vapor deposition method followed by a solvothermal process. The unique three-dimensional nanostructures of MoS2/VGNS arranged in a vertically aligned manner can be easily constructed on various substrates, including Ni foam and graphite paper. Compared with MoS2/carbon black, MoS2/VGNS nanocomposites grown on Ni foam exhibit enhanced electrochemical performance as the anode material of lithium-ion batteries, delivering a specific capacity of 1277 mAh g−1 at a current density of 100 mA g−1 and a high first-cycle coulombic efficiency of 76.6%. Moreover, the MoS2/VGNS nanostructures also retain a capacity of 1109 mAh g−1 after 100 cycles at a current density of 200 mA g−1, suggesting excellent cycling stability. In addition, when the MoS2/VGNS nanocomposites grown on graphite paper are applied in the hydrogen evolution reaction, a small Tafel slope of 41.3 mV dec−1 and a large double-layer capacitance of 7.96 mF cm−2 are obtained, which are among the best values achievable by MoS2-based hybrid structures. These results demonstrate the potential applications of MoS2/VGNS hybrid materials for energy conversion and storage and may open up a new avenue for the development of vertically aligned, multifunctional nanoarchitectures. Transforming normally flat graphene into vertical structures makes it easier to enhance energy devices using nanostructured semiconductors. Recent studies have revealed that graphene can be produced from surprising sources — for example, butter molecules can be turned into few-layered graphene sheets that align perpendicular to surfaces using a combination of plasma radiation and chemical vapor deposition. Hui Ying Yang and co-workers from Singapore University of Technology and Design have discovered that butter-derived vertical graphene nanosheets (VGNS) can also act as platforms for growing molybdenum disulfide (MoS2), an inorganic material with potent electrochemical activity. The team used a solvothermal reaction to sprout ‘nanoleaves’ of MoS2 onto VGNS without needing polymeric binders. The MoS2/VGNS hybrid proved adept at improving lithium-ion battery capacity and rate capability, as well as boosting the production of hydrogen gas in water electrolysis. MoS2-coated vertical graphene nanosheet nanocomposites are successfully designed and synthesized as high-performance electrode materials for both lithium-ion batteries and hydrogen production. The unique three-dimensional hybrid structure is the key to the high performance for energy storage and conversion.