Effect of microstructure on HER catalytic properties of MoS₂ vertically standing nanosheets

MoS₂ vertically standing nanosheets were prepared by metal-organic chemical vapor deposition using molybdenum hexacarbonyl (Mo(CO)₆) and 1,2-ethanedithiol (C₂H₆S₂) as precursors. The sulfur source was chosen as a less toxic alternative to the well-established hydrogen sulfide (H₂S). These films were deposited between 500 and 800 °C resulting in different surface morphologies, from nanoparticles to vertically standing nanosheets. A highly (002) oriented 2H-MoS₂ film was obtained at 700 °C. The effect of the microstructure on the catalytic performance of hydrogen evolution reaction (HER) of the MoS₂ films was investigated. The Tafel slope varied from 68 to 94 mV/dec, showing that the microstructure of the films had an influence on their final electrochemical performance. Water contact angle analysis was used to study the surface wettability of the films, obtaining values from 60 to 121.2°. These results exhibited a quite consistent trend with the Tafel slope, indicating a significant effect of wettability and nanosheets edge exposure on the HER performance.