Disclosure of charge storage mechanisms in molybdenum oxide nanobelts with enhanced supercapacitive performance induced by oxygen deficiency

Molybdenum oxide(MoO_(3)), with superior features of multi-electrochemical states, high theoretical capacitance, and low cost, is a desirable supercapacitor electrode material but suffers from low conductivity and insufficient active sites. The MoO_(3) capacitance can be largely amplified by introducing oxygen(O) vacancies, but the mechanisms at the atomic scale are still ambiguous.Herein, O vacancies are created at the O2 and O3 sites in the MoO_(3) nanobelts by carbonization to maximize the supercapacitance in the MoO_(2.39). The supercapacitive storage is mainly ascribed to the proton adsorption at the O1 sites to create Mo–OH, leading to an expansion of the interlayer spacing along the lattice B-axis. Roughly 98% of the initial supercapacitance is retained after 1000 cycles,due to the reversible change in the interlayer spacing. Our results provide an insight into the oxygen deficiency-related mechanisms of the supercapacitive performance at the atomic scale and devise a facile method to enhance the supercapacitance for energy storage and conversion.