Oxygen deficiency and single-crystalline MoO3−x nanobelt as advanced supercapacitor negative electrode and dye adsorbent

Molybdenum trioxide (MoO3) is known as a promising pseudocapacitive material, which can provide large capacitance through reversible redox reactions. However, the low conductivity, deficient surface-active sites and sluggish ion diffusion limit its practical capability. Herein, single crystal and oxygen vacancy-enriched α-MoO3−x nanobelt is established via a facile one-pot hydrothermal approach. The transmission electron microscope and the electron paramagnetic resonance confirm the single-crystalline nature and rich oxygen vacancy of α-MoO3−x nanobelt. The electrochemical experiments reveal that α-MoO3−x displays an enhanced specific capacitance (912.5 F g−1 at 1 A g−1) than stoichiometric MoO3, which is among the top value and next to the theoretical capacitance (1256 F g−1). Such increased electrochemical capability is derived from the oxygen vacancy and single crystal structure with more exposed active sites and increased conductivity. Moreover, the adsorption experiments also show the superiority of MoO3−x over stoichiometric MoO3 in adsorbing capacity and adsorption rate. Structural analysis reveals that the enlarged interlayer spacing could weak the Van der Waals force, providing more adsorption sites and enhancing the adhesive of molecules. This work paves the way for fabricating advanced materials with specific architecture for promising high-capacitance electrode and adsorbent.