Tuning the Composition and Structure of Amorphous Molybdenum Sulfide/Carbon Black Nanocomposites by Radiation Technique for Highly Efficient Hydrogen Evolution.

Amorphous molybdenum sulfide/carbon black (MoS/C) nanocomposites are synthesized by a facile one-step γ-ray radiation induced reduction process. Amorphous MoS shows better intrinsic activity than crystalline MoS. And the composition and amorphous structure of MoS could be expediently tuned by absorbed dose for excellent catalytic activity. Meanwhile, the addition of carbon black leads to a significant decrease of charge transfer resistance and increase of active sites of MoS/C composite. Consequently, MoS/C nanocomposite shows Pt-like catalytic activity towards hydrogen evolution reaction (HER), which requires an onset over potential of 40 mV and over potential of 76 mV to achieve a current density of 10 mA cm, and the corresponding Tafel slope is 48 mV decade. After 6000 CV cycles, the catalytic activity of MoS/C shows no obvious decrease. However, when platinum (Pt) foil is used as counter electrode, MoS/C composite show better catalytic activity abnormally after long-term cycling tests. The dissolution of Pt was observed in HER and the Pt dissolution mechanism is elucidated by further analyzing the surface composition of after-cycling electrodes, which offers highly valuable guidelines for using Pt electrode in HER.