Mo2C@NC@MoSx porous nanospheres with sandwich shell based on MoO42--polymer precursor for efficient hydrogen evolution in both acidic and alkaline media

Mo2C@NC@MoSx porous nanospheres with sandwich shell have been synthesized for efficient hydrogen evolution in both acidic and alkaline media. Firstly, porous MoO2-Mo2C@NC nanospheres have been obtained with ultrafine Mo2C nanocrystallines as core and ultrathin N-doped carbon (NC) as shell through the carbonization of MoO42--/aniline-pyrrole (MoO42--Polymer) as precursor. Secondly, Mo2C@NC@MoSx porous nanospheres with sandwich shell have been synthesized by hydrothermal sulfurization, which can be confirmed by XPS and HRTEM. The sandwich shell is composed of ultrathin MoSx, NC layer and Mo2C nanocrystallines, which may reduce the strong MoH bonding energy of pure Mo2C and lead to the suitable ΔGH* for HER. In addition, the ultrathin NC can prevent the aggregation of active sites and improve charge transfer rate due to rich N-doping. Mo2C@NC@MoSx exhibits enhanced performance and long-time durability in both acidic and alkaline solution. It requires a low onsetpotential of 119 mV, Tafel slope of 56 mV dec−1 in acidic solution and onsetpotential of 86 mV, Tafel slope of 90 mV dec−1 in alkaline solution. Therefore, designing sandwich nanostructure with better conductivity and optimized MoH bonding energy may be a promising strategy for excellent Mo-based HER electrocatalysts.

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