Activation of nitrogen species mixed with Ar and H2S plasma for directly N-doped TMD films synthesis

Among the transition metal dichalcogenides (TMD), tungsten disulfide (WS2) and molybdenum disulfide (MoS2) are promising sulfides for replacing noble metals in the hydrogen evolution reaction (HER) owing to their abundance and good catalytic activity. However, the catalytic activity is derived from the edge sites of WS2 and MoS2, while their basal planes are inert. We propose a novel process for N-doped TMD synthesis for advanced HER using N-2 + Ar + H2S plasma. The high ionization energy of Ar gas enabled nitrogen species activation results in efficient N-doping of TMD (named In situ-MoS2 and In situ-WS2). In situ-MoS2 and WS2 were characterized by various techniques (Raman spectroscopy, XPS, HR-TEM, TOF-SIMS, and OES), confirming nanocrystalline and N-doping. The N-doped TMD were used as electrocatalysts for the HER, with overpotentials of 294 mV (In situ-MoS2) and 298 mV (In situ-WS2) at a current density of 10 mA cm(-2), which are lower than those of pristine MoS2 and WS2, respectively. Density functional theory (DFT) calculations were conducted for the hydrogen Gibbs energy ( increment G(H)) to investigate the effect of N doping on the HER activity. Mixed gas plasma proposes a facile and novel fabrication process for direct N doping on TMD as a suitable HER electrocatalyst.

Automated summary

Among transition metal dichalcogenides (TMD), tungsten disulfide (WS2) and molybdenum disulfide (MoS2) show promise as sulfides for replacing noble metals in the hydrogen evolution reaction (HER) due to their abundance and good catalytic activity. This research proposes a novel process for N-doped TMD synthesis using N-2 + Ar + H2S plasma, resulting in efficient N-doping of WS2 and MoS2. The N-doped TMD exhibit lower overpotentials in the HER compared to pristine MoS2 and WS2, making them suitable electrocatalysts.