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

2D transition metal nitrides, especially nitrogen-rich tungsten nitrides (WxNy, y > x), such as W3N4 and W2N3, 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-W2N3 (h-W2N3) flakes are synthesized at atmospheric pressure via a salt-templated method. The formation energy of h-W2N3 can be dramatically decreased owing to the strong interaction and domain matching epitaxy between KCl and h-W2N3. 2D h-W2N3 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).