One-Step Surface-Plasma-Induced Exfoliation of the Graphite/WS₂ Bilayer into Homogeneous Two-Dimensional Graphene/WS₂ Nanosheet Composites as Catalysts for the Hydrogen Evolution Reaction

In this paper, a unique method for one-step surface-plasma-induced exfoliation of a graphite/bulk transitional-metal dichalcogenide (TMD) bilayer for the preparation of graphene (Gs)/TMD nanosheet composites is presented, using Gs–tungsten disulfide (WS2) nanocomposites that functioned as electrocatalysts for the hydrogen evolution reaction (HER) as our case study. This approach of producing nanocomposites is universal for all TMD materials with a graphite substrate layer that generates surface plasma when serving as the cathode under 65 V in a 1 M H2SO4 or KOH electrolyte at 90 °C for 50 min. After characterizing the resultant binary nanocomposites, we found that the optimal HER performance occurred for the resultant binary nanocomposites (GW3–H2SO4) that is produced from a graphite/bulk WS2 bilayer (thickness ratio 0.13:0.03 mm) with 1 M H2SO4 as the electrolyte; it has a low overpotential of 180 mV at a current density of 10 mA cm–2 with a low Tafel slope of 76 mV dec–1 and with high stability up to 30 h. This cost-effective and scalable one-step technique—combining two dissimilar two-dimensional nanostructured composites—for electrocatalytic applications appears to be an efficient means of fabricating Gs/TMD nanosheet composites suitable for use as HER electrocatalysts.