Facile Synthesis of Tungsten Diboride (WB<sub>2</sub>‑191) in Molten Salt and Its Hydrogen Evolution Performance\nin Acidic and Alkaline Media

The\nAlB<sub>2</sub>-type WB<sub>2</sub>-191 with only graphene-like\nflat boron layers is deemed to be an ideal electrocatalyst for hydrogen\nevolution. However, such investigation is severely hindered by the\nlack of facile synthesis methods for this type of WB<sub>2</sub>-191.\nHerein, we report the successful synthesis of AlB<sub>2</sub>-type\nWB<sub>2</sub>-191 by a one-step molten salt method via the reaction\nof WCl<sub>6</sub> and NaBH<sub>4</sub> in LiCl–KCl molten\nsalt at 800 °C under atmospheric pressure. The as-synthesized\nWB<sub>2</sub>-191 presents a nanosheet structure, as demonstrated\nby the scanning electron microscope and transmission electron microscopy\nresults with a large BET surface area of 63 m<sup>2</sup>/g. Such\nWB<sub>2</sub>-191 nanosheets exhibit remarkable hydrogen evolution\nreaction activity, delivering low overpotentials of 121 in 0.5 H<sub>2</sub>SO<sub>4</sub> and 147 mV in 1.0 M KOH to drive 10 mA/cm<sup>2</sup>, which is superior to any previously reported binary tungsten\nborides. Furthermore, an outstanding stability was shown over 70 h\nof potentiostatic operations in both acidic and alkaline electrolytes.