Facile synthesis of WS2 hollow spheres and their hydrogen evolution reaction performance

We introduced a facile method for the fabrication of WS2 hollow spheres and used the spheres as efficient catalysts for hydrogen evolution reaction. First, thioacetamide nanocrystals were crystallized from a saturated solution as the temperature was reduced from 40 to 25 degrees C. These nanocrystals acted as initial cores for inducing WS2 hollow spheres. Next, thioacetamide-WCl6 core-shells were formed upon adding WCl6 into the prepared precursor. Through hydrolysis, the thioacetamide nanocrystals were decomposed to generate H2S and NH3 gases, which in turn caused the expansion and sulfurization of WCl6 simultaneously, giving rise in WS2 hollow spheres. The diameters of the as-prepared WS2 hollow spheres were in the range of 300 nm to 2 mu m. The performance of WS2 hollow spheres as catalysts for hydrogen evolution reactions was evaluated and compared with that of WS2 nanoflowers. Interestingly, WS2 hollow structures exhibited an onset potential of 125 mV and a Tafel slope of 60 mV dec(-1), which was lower than that of WS2 nanoflowers (82.3 mV dec(-1)). Furthermore, the conductivity of WS2 hollow structures was higher than that of WS2 nanoflowers, as confirmed by impedance spectroscopy. These results indicate that the WS2 hollow spheres are promising candidates for energy conversion and storage applications.