Tuning oxygen-containing functional groups of graphene for supercapacitors with high stability

To investigate the relationship between the oxygen-containing functional groups of graphene and the stability of supercapacitors, reduced graphene oxide (rGO) containing different oxygenic functional groups was prepared by varying the reduction time of GO using hydrazine as the reducing agent. TEM, XRD, Raman, and XPS characterizations revealed that, as the reduction time increased, the sp(2) structure in the rGO sheet was restored and the obtained rGO had good crystallinity accompanied by removal of the oxygenic functional groups. The analysis of the content of the different functional groups also suggested that the reduction rate of the oxygenic functional group was C-O > C=O > O=CO. The supercapacitive performance of rGO showed that the oxygenic functional groups contributed to some pseudocapacitance and resulted in a larger specific capacitance. At the same time, however, it is also accompanied by poorer rate performance and durability, which will be improved by removing the oxygenic functional groups by extending the reduction time. With an optimized reaction condition of a reduction time of 24 h, the obtained rGO exhibited excellent stability in floating tests at 3.0 V and 45 & DEG;C for 60 days. These findings pave the way for the development of high quality graphene materials for cost-effective and practical graphene supercapacitors.

Automated summary

The relationship between oxygen-containing functional groups in graphene and supercapacitor stability was investigated. Different oxygenic functional groups were introduced in reduced graphene oxide (rGO) by varying the reduction time. The study revealed that longer reduction time resulted in restoration of the sp(2) structure in the rGO sheet, increased crystallinity, and removal of oxygenic functional groups. The presence of oxygenic functional groups contributed to pseudocapacitance and larger specific capacitance, but also led to poorer rate performance and durability. By extending the reduction time, the oxygenic functional groups can be effectively removed and the stability of rGO can be improved.