One-Step Surface-Plasma-Induced Exfoliation of the Graphite/WS₂Bilayer into Homogeneous Two-Dimensional Graphene/WS₂Nanosheet 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.