Enhancing the storage capacity of tungsten oxides by gaseous nitriding

Tungsten nitride (WN) is a compelling candidate for high-performance supercapacitors, yet its practical application is often hindered by morphological limitations and precursor aggregation. This study presents a targeted synthesis strategy to overcome these challenges by engineering the morphology of the tungsten oxide (WOx) precursor prior to ammonia nitridation. By systematically tuning the molar ratio of potassium sulfate and the concentration of hydrochloric acid during hydrothermal synthesis, we achieved a highly uniform, flower-like precursor architecture composed of interconnected nanorods. We demonstrate that this specific precursor morphology is critical; unlike irregular granular structures, the flower-like nanorods undergo controlled lattice contraction and delamination during nitridation, evolving into a highly porous, conductive cubic WN network. This structural evolution creates abundant channels for electrolyte infiltration, thereby significantly enhancing ion-diffusion kinetics. Consequently, the optimized WN electrode exhibits a superior specific capacitance of 191.95 F/g (at 5 mV/s) and robust electrochemical stability. These findings underscore the importance of precursor design in nitride synthesis, offering a reproducible pathway to unlock the full potential of transition-metal nitrides in energy storage applications.