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

Here we demonstrate the effect of the concentration of hydrogen peroxide solution on the generation of various kinds of oxygen ions, mainly peroxide (O-2(2-)) and superoxide (O-2(-)) ions, on the surface of molybdenum trioxide (MoO3) nanobelts. Due to O-2(2-) and O-2(-) 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 (O-2(-), O-2(2-), Mo5+ and Mo6+) that are available to interact with the electrolyte ions. By altering the concentration of the surface species (I-O2(-)/I-O2(2-), I-Mo(5+)/I-Mo(6+)), a specific capacitance as high as 210 Fg(-1) is achieved for MoO3 nanobelts at an applied current density of 0.5 Ag-1, with relatively good cycling stability (approximate to 85%) after 2000 cycles