Research On 3D Graphene Supercapacitors And Flexible Sonic Sensors

Graphene possesses many extraordinary properties, such as high mechanical strength, excellent transmittance, superb thermal conductivity, high electrical conductivity and huge specific surface area, which have led to many kinds of applications in energy storages and sensors. Graphene can be used as Supercapacitor electrodes with good performance, which could be ascribed to two aspects:(1) the EDLC effects between graphene and electrolyte;(2) the pseudo capacitance from graphene composited with other materials. Besides, because of the excellent Young’s modulus and conductive properties, graphene also has potential application in mechanical sensors.In this master thesis, to improve the conductivity of supercapacitors electrodes and shorten ion transport distance, the effect of different materials of 3D graphene, which was prepared by CVD methods using ethanol as carbon source and nickel foam as templet, composited with Ni(OH)2 and V2O5 on the performance of supercapacitor is described. On the other hand, the performance of materials of PDMS filled in 3D graphene is also described as a flexible sonic sensor.(1) 3D graphene/Ni(OH)2 composites with the different morphologies were respectively synthesized by in-situ electrodeposition in the presence of different surfactants(SDBS, PTSA, ethanol). The electrochemical analysis results reveals that 3D graphene/Ni(OH)2 material with morphology of nanoflowers exhibit high specific capacitance 718.2 F/g at 6.7A/g and good cycling performance with 84.2% capacitance retention after 500 cycles compared to other 3D graphene/Ni(OH)2 materials.(2) The complex precursor of 3D graphene and V2O5 was prepared using hydrothermal method with the surfactant of polyvinylpyrrolidone(PVP). After annealing in air, the 3D graphene/ V2O5 composite with morphology of nano-silice arrays was obtained. Three-electrode electrochemical measurement shows that the capacitance value of this composite can reach 96.3 F/g at 0.1 A/g and capacitance retention is 112.3% at 2 A/g after 1000 cycles.(3) The sonic sensor was synthesized by 3D graphene filled with PDMS(polydimethylsiloxane). The tuning forks under three different frequencys and the vibration signals of PZT(Piezoelectric Ceramic Transducer) were measured with the prepared sonic sensor, and the excellent signal waveform was obtained. The results show that the sensor can produce large amplitude of output signal for the mechanical deformation with long response time; on the other hand, for the signal vibration coupled into the sensor, the amplitude of output signal is small and the response time is short, even less than 10-6 s.