Low-temperature synthesis of molybdenum sulfides, tungsten sulfides, and composites thereof as efficient electrocatalysts for hydrogen evolution reaction

Abstract

In this work, we report a one-step approach for synthesizing molybdenum sulfides and tungsten sulfides, using (N2H5)2MS4 (M = Mo, W) as highly energetic self-catalytic redox precursors and inducing a thermolysis process at various temperatures. These materials’ thermodynamic advantages facilitate the formation of molybdenum/tungsten sulfides at low temperatures. As expected, MoSx-100 °C (which features the [Mo3S13]2− active site model) exhibits the highest catalytic activity of the reported molybdenum sulfides. In addition, an optimized sample of crystalline WS2 was reported to produce hydrogen at 400 °C. Furthermore, the combination of carbon materials significantly enhanced the hydrogen production performance. The optimal sample of reduced graphite oxide (rGO)/MoSx-100 °C required an overpotential of only 125 mV to achieve a current density of 10 mA cm−2 and a shallow Tafel slope of 48.8 mV dec−1; this was attributed to the increased charge transfer from rGO. Furthermore, the catalyst exhibited good stability after 2000 cycles and 12 h of testing. This work may provide an alternative approach for the large-scale synthesis of transition metal dichalcogenides in high-performance catalyst applications.