Enhancing the storage capacity of tungsten oxides by gaseous nitriding

Abstract

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 (WO_x) 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.