Introducing Electrochemically Active Oxygen Species to Boost the Pseudocapacitance of Carbon‐based Supercapacitor

Abstract Low energy density is the main bottleneck for carbon‐based supercapacitors, which can be addressed by introducing extra faradaic pseudocapacitance. Herein, a cyclic voltammetry oxidation method in 1 M H 2 SO 4 electrolyte was employed for carbon electrode to produce electrochemically active oxygen functional groups that are in contact with the conductive substrates, which facilitates the implementation of the pseudocapacitance. Moreover, the influence of potential window and sweep rate on the components and performances of oxidized electrodes in the cyclic voltammetry oxidation process was systematically investigated. The results reveal that a broad potential window of −0.65∼2 V can enhance the oxygen content to 16.4 wt.% (vs. 7.6 wt.% within −0.65∼1.5 V). Additionally, a selective oxygen component dominated with redox active C−OH and C=O groups was achieved by a rapid potentiodynamic sweep at 20 mV s −1 , simultaneously suppressing the ‐COOH groups with inferior conductivity. The oxidized AC electrodes could substantially improve the specific capacitance (534 vs. 150.3 F g −1 at 1 A g −1 ) without sacrifice of rate performance (retained 418 F g −1 at 20 A g −1 ), accompanying excellent cycling stability of 94 % of initial capacitance after 10000 cycles. Such finding would provide some reference for tailoring oxygen species to fabricate advanced carbon‐based supercapacitor electrodes.