Microwave-assisted Synthesis of rGO/CeO2 Supercapacitor Electrode Materials with Excellent Electrochemical Properties

CeO2 possesses excellent pseudocapacitance, nevertheless the electrochemical properties of carbon/CeO(2 )composites need to be improved. In this paper, reduced graphene oxide (rGO)/CeO2 composite is prepared via a simple microwave-assisted synthesis method. The typical synthesis process is as follows. Firstly, 60 mg of graphene oxide was dissolved into 50 mL of deionized water. Then 20 mL of 0.17 mol.L-1 Ce(NO3)3.6H(2)O solution was added wider ultrasonic conditions. The electrostatic assembly led to the combination of the graphene oxide and Ce(NO3)(3). Afterwards, 10 mL of 1.5 mol.L-1 KOH was added dropwise into the mixed solution until the pH value up to 10. The rGO/CeO(2 )was synthesized in the above-mentioned mixed solution by using the microwave heating method. The heating time was set for 45 s. Repeated the microwave heating process for five times after the solution cooled down to the room temperature. Finally, the rGO/CeO2 was harvested by centrifugation, washing and freeze-drying. The CeO2, in the form of particles, distributes uniformly and conformally on the surface of the corrugated rGO by the morphology observation. The existence of the tiny gaps is displayed between the nano-scaled CeO2 particles. N-2 adsorption/desorption analysis suggests that the rGO/CeO2 has large specific area and pores in the mesoporous size, which is helpful to the sufficient contact with the electrolyte. By the electrochemical measurements, the specific capacitance of the rGO/CeO(2)is as high as 468 F.g(-1) and the capacity retention is up to 107.3% after 10000 charge/discharge cycles. The excellent cycling stability is attributed to the good synergistic effect between the rGO with large specific area and the CeO(2 )with uniform and thin layer, which decreases the resistance of ion transport, and the tiny gaps between CeO(2 )particles, which mitigates the lattice expansion during the transformation from Ce4+ to Ce3+. The energy density of the assembled symmetrical supercapacitor rGO/CeO2 parallel to rGO/CeO(2)reaches 18.16 Wh.kg(-1). As a supercapacitor electrode material, the rGO/CeO(2 )has wide prospect.