Size-selected molybdenum sulfide (MoSx) nanoclusters obtained by magnetron sputtering and gas condensation on glassy carbon substrates are typically sulfur-deficient (x = 1.6 ± 0.1), which limits their crystallinity and electrocatalytic properties. Here we demonstrate that a sulfur-enriching method, comprising sulfur evaporation and cluster annealing under vacuum conditions, significantly enhances their activity towards the hydrogen evolution reaction (HER). The S-richness (x = 4.9 ± 0.1) and extended crystalline order obtained in the sulfur-treated MoSx nanoclusters lead to consistent 200 mV shifts to lower HER onset potentials, along with two-fold and more-than 30-fold increases in turnover frequency and exchange current density values respectively. The high mass activities (∼111 mA mg−1 @ 400 mV) obtained at ultra-low loadings (∼100 ng cm-2, 5% surface coverage) are comparable to the best reported MoS2 catalysts in the literature.
- Hydrogen evolution
- Magnetron sputtering deposition
- Molybdenum sulfide
ASJC Scopus subject areas
- Environmental Science(all)
- Process Chemistry and Technology