Electrochemical performance of magnetic nanoparticle-decorated reduced graphene oxide (MRGO) in various aqueous electrolyte solutions

The objective of this work is twofold: (1) to improve the electrochemical performance of reduced graphene oxide (RGO) by decorating RGO sheets with magnetic nanoparticles (MNPs) and (2) to evaluate the electrochemical performance of RGO and MNP-decorated RGO (MRGO) in various aqueous electrolyte solutions (phosphate buffer solution (PBS) containing ferricyanide, PBS containing ferricyanide and KCl, Na2SO4, and KOH). The morphological and structural characteristics of solvothermal synthesized RGO and MRGO revealed the decoration of phase pure Fe3O4 nanoparticles on RGO sheets. In FC-PBS-KCl electrolyte solution, MRGO showed higher redox peak current (83.89 mu A) and lower peak potential separation (0.11 V) at 50 mV s(-1) scan rate compared with that in FC-PBS electrolyte solution. MRGO showed 15.5% higher peak current than that for the RGO in FC-PBS-KCl electrolyte solution. Moreover, the peak current for MRGO in FC-PBS-KCl was increased by 30% when compared with that in FC-PBS electrolyte solution. These results suggest that MRGO in FC-PBS-KCl electrolyte solution can be a good electron pathway between electrode and electrolyte solution for sensing applications. On the other hand, in both Na2SO4 and KOH electrolyte solution, RGO and MRGO showed supercapacitive behavior. In KOH, MRGO exhibited higher specific capacitance (180 Fg(-1) at 3 A g(-1)) and superior cyclic stability (87% after 2000 cycles) compared with that in Na2SO4. MRGO showed 219% increase in specific capacitance than that of the RGO in KOH electrolyte solution. The superior electrochemical performance of MRGO compared with that of RGO is attributed to the synergistic effect of conductivity of RGO and redox activity of MNPs.