Facile Synthesis of Tungsten Diboride (WB2-191) in Molten Salt and Its Hydrogen Evolution Performance in Acidic and Alkaline Media

The AlB₂-type WB₂-191 with only graphene-like flat boron layers is deemed to be an ideal electrocatalyst for hydrogen evolution. However, such investigation is severely hindered by the lack of facile synthesis methods for this type of WB₂-191. Herein, we report the successful synthesis of AlB₂-type WB₂-191 by a one-step molten salt method via the reaction of WCl₆ and NaBH₄ in LiCl–KCl molten salt at 800 °C under atmospheric pressure. The as-synthesized WB₂-191 presents a nanosheet structure, as demonstrated by the scanning electron microscope and transmission electron microscopy results with a large BET surface area of 63 m²/g. Such WB₂-191 nanosheets exhibit remarkable hydrogen evolution reaction activity, delivering low overpotentials of 121 in 0.5 H₂SO₄ and 147 mV in 1.0 M KOH to drive 10 mA/cm², which is superior to any previously reported binary tungsten borides. Furthermore, an outstanding stability was shown over 70 h of potentiostatic operations in both acidic and alkaline electrolytes.