Synthesis of MnO_2-graphene composites with enhanced supercapacitive performance via pulse electrodeposition under supergravity field

摘要

A method of pulse electrodeposition under supergravity field was proposed to synthesize MnO_2- graphene composites. Supergravity is very efficient for promoting mass transfer and decreasing concentration polarization during the electrodeposition process. The synthesis was conducted on our homemade supergravity equipment. The strength of supergravity field depended on the rotating speed of the ring electrode. 3D flower like MnO_2 spheres composed of nanoflakes were acquired when the rotating speed was 3000 rpm. Graphene nanosheets play as a role of conductive substrates for MnO_2 growing. The composites are evaluated as electrode materials for supercapacitors. Electrochemical results show that the maximum specific capacitance of the MnO_2-graphene composite is 595.7 F g~(-1) at a current density of 0.5 Ag~(-1). In addition, the composite exhibits excellent cycle stability with no capacitance attenuation after 1000 cycles. The approach provides new ideas for developing super- capacitor electrode materials with high performance.