Oxygen‐Ions‐Mediated Pseudocapacitive Charge Storage in Molybdenum Trioxide Nanobelts

Abstract Here we demonstrate the effect of the concentration of hydrogen peroxide solution on the generation of various kinds of oxygen ions, mainly peroxide (O₂²⁻) and superoxide (O₂⁻) ions, on the surface of molybdenum trioxide (MoO₃) nanobelts. Due to O₂²⁻ and O₂⁻ ions, the mechanism of charge storage shows an interplay between surface‐controlled and diffusion‐controlled redox reactions. The concentration of H₂O₂ is indicative of the strength of hydrogen bonding, which significantly affects the concentration or coordination of the surface species (O₂⁻, O₂²⁻, Mo⁵⁺ and Mo⁶⁺) that are available to interact with the electrolyte ions. By altering the concentration of the surface species (I_O2⁻/I_O2²⁻, I_Mo⁵⁺/I_Mo⁶⁺), a specific capacitance as high as 210 F g⁻¹ is achieved for MoO₃ nanobelts at an applied current density of 0.5 A g⁻¹, with relatively good cycling stability (≈85 %) after 2000 cycles.