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

Abstract

Molybdenum oxide (MoO3), 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 MoO3 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 MoO3 nanobelts by carbonization to maximize the supercapacitance in the MoO2.39. 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.