MSE GT-PKU Joint PhD Proposal – Zhenkun Wu

Date: Friday, November 28, 2014

Time: 2:30 PM

Location: Peking University

Committee:

Dr. Ching-Ping Wong, co-advisor (GT)

Dr. Shulin Bai, co-advisor (PKU)

Dr. Pingchou Han (PKU)

Dr. Zhong Lin Wang (GT)

Dr. Anyuan Cao (PKU)

Title: benzene-derivatives/graphene based supercapacitors and metal-reduced graphene ac line-filters

Abstract: Various aromatic molecules have been used to improve the performance of reduced graphene oxide (rGO) based supercapacitors. However, the underlying mechanism for the improvement is unclear. In our case, we carefully design a facile approach that not only increases the specific capacitance dramatically but also clearly identifies the main reason for the enhancement. We find that the capacitance increase mainly arises from the pseudocapacitance of specific benzene derivative molecules rather than their spacing effect. Moreover, the para and ortho substituted benzene derivatives contribute much more than the meta substituted ones. With the addition of PPD, we achieve a specific capacitance of 273 F/g that is much higher than that of pure rGO electrodes (113 F/g).  The hybrid electrode also shows great stability with a capacitance retention of up to 86% after 10000 charge-discharge cycles. The conformal reduction and assemble of rGO on metal electrodes makes it suitable for scalable production of solid flexible micro-supercapacitors. The as-prepared MSC shows a specific areal capacitance of 0.95 mF/cm2 and maintains 98.3% after 11000 times of charge/discharge cycles. In addition, extremely small relaxation time constant of 4.8 ms is achieved in gelled electrolyte, which indicates high ion transfer mobility within the structure. The device also exhibits great flexibility which retains 93.5% of the capacitance after 5000 times of bending and twisting. The device exhibits a phase of -75.4º at 120 Hz with a specific areal capacitance much larger than that of commercial aluminum electrolytic capacitors (316 µF/cm2).  These properties make the as-fabricated MSC promising for energy storage as well as line-filtering in wearable electronics.