Alternative synthesis of structurally defective MoS2 nanoflakes for efficient hydrogen evolution reaction

[Display omitted] •MoS2 was prepared by hydrothermal method using excessive oxalic acid concentration.•Nature of synthesis creates a defective MoS2 structure.•Structurally defective MoS2 is highly active towards HER in acidic solution. Two-dimensional layered molybdenum sulfide (MoS2) is highly attractive as electrocatalyst for high purity hydrogen production because of its intrinsic properties and favorable cost-benefit ratio. Notably, electrocatalytic activity of MoS2 strongly depends on exposed edges and density of defect sites. Here, we report the preparation of MoS2 nanoflakes through an oxalic acid assisted-hydrothermal method. A comparatively excessive amount of oxalic acid was used as an alternative strategy for the preparation of MoS2. XRD, TEM, RAMAN, and XPS results revealed that as-prepared MoS2 is highly defective with presence of unsaturated S and abundant exposed edges. As a result, structurally defective MoS2 nanoflakes exhibit high activity for HER with low overpotential of 214 mV at 10 mA/cm2, a small Tafel slope of 52 mV/decade and excellent stability.