Synthesis of non-planar graphene-wrapped copper nanoparticles with iron(III) oxide decoration for high performance supercapacitors.

The performance of supercapacitors strongly depends on the electrochemical characterizations of electrode materials. Herein, a composite material consisted of iron(III) oxide (Fe2O3) and multilayer graphene-wrapped copper nanoparticles (Fe2O3/MLG-Cu NPs) is fabricated on a flexible carbon cloth (CC) substrate via two-step synthesis process for supercapacitor application. Where, MLG-Cu NPs are prepared on CC by one-step chemical vapor deposition (CVD) synthesis approach; thereafter, the Fe2O3 is further deposited on the MLG-Cu NPs/CC via successive ionic layer adsorption and reaction (SILAR) method. The related material characterizations of Fe2O3/MLG-Cu NPs are well investigated by scanning electron microscopic (SEM), high resolution transmission electron microscopy (HR-TEM), Raman spectrometer and X-ray photoelectron spectroscopy (XPS); the electrochemical behaviors of the pertinent electrodes are studied by cyclic voltammogram (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements. The flexible electrode with Fe2O3/MLG-Cu NPs composites exhibits the best specific capacitance of 1092.6 mF cm-2 at 1 A g-1, which is much higher than those of electrodes with Fe2O3 (863.7 mF cm-2), MLG-Cu NPs (257.4 mF cm-2), multilayer graphene hollow balls (MLGHBs, 14.4 mF cm-2) and Fe2O3/MLGHBs (287.2 mF cm-2). Fe2O3/MLG-Cu NPs electrode also exhibits an excellent GCD durability, and its capacitance remains 90% of its original value after 1200 cycles of the GCD process.　Finally, a supercapacitor system consisted of four Fe2O3/MLG-Cu NPs/CC electrodes can efficiently power various light-emitting diodes (i.e., red, yellow, green, and blue lights), demonstrating the practical application of Fe2O3/MLG-Cu NPs/CC electrode.