Twinned Tungsten Carbonitride Nanocrystals Boost Hydrogen Evolution Activity and Stability

Abstract 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 W₂C 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 W₂C 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 W₂C alone. To complement the experimental observation, the theoretical calculations demonstrate that the WCN endows more favorable hydrogen evolution reaction than the single W₂C or WN crystals due to abundant interfaces, beneficial electronic states, lower work function, and more active W sites at the N–W–C interfaces.