Supercapacitor Performance of Expanded Magnetic Graphene Composites

• Main Authors: Mahmoud Mohamed Mahmoud Ahmed, 馬哈茂德
• Other Authors: Toyoko Imae
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/11290550924679329074

博士 === 國立臺灣科技大學 === 應用科技研究所 === 104 === Magnetic graphene (MGC) composite derived from stage-1 FeCl3–graphite intercalation compounds (GIC) was thermally treated up to 75 min at 400 °C and for 2 min at 900 °C in air. The heat treatments of the composite induced the cubical expansion of graphene with the enlargement of inter-graphene distances. Heating played a considerable role in the increase in surface area that reached 17.2 m2 g−1 during the nondefective inter-graphene exfoliation. Accordingly, the specific capacitance of MGC composite increased up to 840% of its initial value upon heating of pristine MGC composite in comparison with its value before heat treatment. Moreover, MGC heated at 900 °C (MGC-900) was hybridized with polyaniline through in situ polymerization of aniline to achieve a specific capacitance of 253 F g−1 at 5 mV s−1. Heat treatment and hybridization with a conductive polymer can effectively produce an efficient-expanded MGC composite with enhanced electrochemical activity and relatively high energy density. Separately, MGC-900 was heated at 2000 °C in vacuum atmosphere, yielding a massive expansion with well-separated layers. This exfoliation produced very thin layers including single and few-layer graphene with a surface area of 53 m2g-1. The exfoliated composite (MGC-900-2000) showed boosted electrochemical performance, with capacitive performance increasing 18 times the original value prior to heating. Additionally, the electrochemical performance of MGC under the effect of magnetic field was investigated. Various magnetic field gradients were thoroughly examined, and the effective DC power was 105 W. Capacitive performance was 40 times higher than the original value. Furthermore, when MGC-900-PANI was investigated, the capacitive routine reached 521 Fg-1 at the same scan rate. These results clearly showed the synergistic effect of the applied magnetic field on graphene exfoliation by improving its electrochemical performance. These three different experiments showed various methods of defect-less graphene exfoliation to promote its synthesis procedure as well as electrochemical performance. Moreover, the electrochemical performance under magnetic field could inaugurate a plethora of the magnetic field in energy science and technology applications.