Atmospheric-Pressure Synthesis of 2D Nitrogen-Rich Tungsten Nitride

2D transition metal nitrides, especially nitrogen-rich tungsten nitrides (W_x N_y , y > x), such as W₃ N₄ and W₂ N₃ , have a great potential for the hydrogen evolution reaction (HER) since the catalytic activity is largely enhanced by the abundant WN bonding. However, the rational synthesis of 2D nitrogen-rich tungsten nitrides is challenging due to the large formation energy of WN bonding. Herein, ultrathin 2D hexagonal-W₂ N₃ (h-W₂ N₃ ) flakes are synthesized at atmospheric pressure via a salt-templated method. The formation energy of h-W₂ N₃ can be dramatically decreased owing to the strong interaction and domain matching epitaxy between KCl and h-W₂ N₃ . 2D h-W₂ N₃ demonstrates an excellent catalytic activity for cathodic HER with an onset potential of -30.8 mV as well as an overpotential of -98.2 mV for 10 mA cm^-2 .