Surface Sulfur Vacancies Induced the Direct Growth of Mesoporous MnS Nanosheets on Three-Dimensional Reduced Graphene Oxide with Ultrahigh Capacity as Electrode Materials for Supercapacitors

Defect engineering is an effective strategy to modulate the electronic structure of electrochemically active materials, which may increase accessible active sites and shorten electrons and ions diffusion path, thus boosting the capacitive performance. In this article, we report the successful synthesis and application of mesoporous γ-MnS nanosheets with surface sulfur vacancies on three-dimensional reduction graphene oxide (3DrGO/MnS-SV) substrates, which exhibits significantly improved electrochemical capacitive performance, including ultrahigh specific capacitance of 27.98 F cm–3 at 0.03 A cm–3 as well as good rate capability and cycling stability. Furthermore, the combination of density functional theory (DFT) calculation and experimental techniques demonstrates that the surface sulfur vacancies not only increase the number of charge carriers adsorption sites but also accelerate the charge carriers transfer processes with low diffusion barrier between the active centers during charge–discharge processes, thus improving the electrochemical properties of the 3DrGO/MnS-SV hybrid nanostructures. In addition, a flexible asymmetric supercapacitor (ASC) based on the 3DrGO/MnS-SV as the positive electrode and N-doping reduction graphene oxide (N-3DrGO) as the negative electrode is successfully assembled. The as-prepared device achieves a high energy density of 2.783 Wh cm–3 at a power density of 0.057 W cm–3 and excellent electrochemical stability (88.5% capacitance retention after 5000 cycles at 5 A g–1). Moreover, the ASC cell shows high flexibility and stability. This work not only can offer a general, effective strategy to fabricate defect-rich electrode material but also can open a new window to rationally designing electrode materials for high-performance energy storage devices.