Highly atom-economic synthesis of graphene/Mn3O4 hybrid composites for electrochemical supercapacitors

Abstract

A highly atom-economic procedure for the preparation of reduced graphene oxide/Mn3O4 (rGO/Mn3O4) composites is reported. Pristine graphene oxide/manganese sulfate (GO/MnSO4) suspension produced by modified Hummers method is utilized with high efficiency, which has been in situ converted into GO/Mn3O4 hybrid composite by air oxidation, then into rGO/Mn3O4 composite by means of dielectric barrier discharge (DBD) plasma-assisted deoxygenation. The Mn3O4 content of the rGO/Mn3O4 composites can be readily tailored. It is observed that Mn3O4 nanoparticles of 15-24 nm are well-dispersed on graphene sheets with Mn3O4 loading as high as 90%. The specific capacitance of the as-prepared rGO/Mn3O4 hybrids with 90% Mn3O4 reaches 193 F g(-1) when employed as the electrode material in neutral Na2SO4 electrolyte solutions (76 F g(-1) for pristine graphene and 95 F g(-1) for pure Mn3O4), which indicates the positive synergetic effects from both graphene and attached Mn3O4. The method developed in this study should offer a new technique for the large scale and highly atom-economic production of graphene/MnOx composites for many applications.

Strongly coupled graphene/Mn 3 O 4 composite with enhanced electrochemical performance for supercapacitor electrode

“…There are abundant functional groups such as carboxyl, hydroxyl and epoxy groups on GO sheets, which have been confirmed by the Fourier transform infrared spectroscopy (FT-IR) technique in previous literature [8,16,30], as illustrated in Fig. 1A.…”

“…A refluent process is carried out. Because of the existence of the large amount of functional groups, the Mn 2+ ions will be well coordinated via an electrostatic force [16]. With the reaction going on, the nucleation and growth of Mn-glycolate will preferentially take place on both sides of the GO sheets derived The Raman scattering spectrum can be used to probe the vibration modes of both crystalline and amorphous materials, providing a complementary structural information to X-ray diffraction [31].…”

“…During the past few decades, the manganese oxides have received much attention as suitable electrode materials for SCs [16]. Among these manganese oxides, hausmannite (Mn 3 O 4 ) has been considered as one of the promising electrode materials for SCs owing to its natural abundance, low cost, environmental compatibility, satisfactory energy storage performance [17,18], and relatively broad work potential window in aqueous solution [8].…”

“…For example, one effective way to solve the inherent defects of Mn 3 O 4 is to synthesize hybrid nanostructures by electrically wiring them up with a highly conductive underlying substrate such as carbon cloth or carbon nanotubes (CNTs) [16].…”

“…These indicate that the capacitance performance of GM composites is greatly enhanced due to the synergetic effects between RGO and Mn3 O 4 NPs. On the one hand, the well-dispersed Mn 3 O 4 nanoparticles can effectively prevent the stacking of graphene sheets, to boost the available surface areas for the storage of charge; On the other hand, graphene, as conductive substrate, not only furnishes the effective electron transfer channels for Mn 3 O 4 , but also devotes double-layer capacitance to the overall energy storage[16,40,41]. Furthermore, the effective reduction of GO by an annealing can further improve the electrochemical conductivity[42], according to the XPS spectrum shown inFig 4b.…”