Twinned Tungsten Carbonitride Nanocrystals Boost Hydrogen Evolution Activity and Stability.

Synergistic integration of two active metal-based compounds can lead to much higher electrocatalytic activity than either of the two individually, due to the interfacial effects. Herein, a proof-of-concept strategy is creatively developed for the successful fabrication of twinned tungsten carbonitride (WCN) nanocrystals, where W2 C and WN are chemically bonded at the molecule level. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) spectroscopy analyses demonstrate that the intergrowth of W2 C and WN in the WCN nanocrystals produces abundant N-W-C interfaces, leading to a significant enhancement in catalytic activity and stability for hydrogen evolution reaction (HER). Indeed, it shows 14.2 times higher and 140 mV lower in the respective turn-over frequency (TOF) and overpotential at 10 mA cm-2 compared to W2 C alone. To complement the experimental observation, the theoretical calculations demonstrate that the WCN endows more favorable hydrogen evolution reaction than the single W2 C or WN crystals due to abundant interfaces, beneficial electronic states, lower work function, and more active W sites at the N-W-C interfaces.