Investigation of Charge Transfer Kinetics at Carbon/Hydroquinone Interfaces for Redox-Active-Electrolyte Supercapacitors

Abstract

The redox-active electrolyte supercapacitor (RAES) is a relatively new type of energy storage device. Simple addition of selected redox species in the electrolyte can greatly enhance the energy density of supercapacitors relative to traditional electric double layer capacitors (EDLCs) owing to redox reactions. Studies on the kinetics at the interface of the electrode and redox mediator are important when developing RAESs. In this work, we employ highly accurate scanning electrochemical microscopy (SECM) to extract the kinetic constants at carbon/hydroquinone interfaces. The charge transfer rate constants are 1.2 × 10 and 1.3 × 10 cm s for the carbon nanotube/hydroquinone and reduced graphene oxide/hydroquinone interfaces, respectively. These values are higher than those obtained by the conventional cyclic voltammetry method, approximately by an order of magnitude. The evaluation of heterogeneous rate constants with SECM would be the cornerstone for understanding and developing high performance RAESs.

Improved performance of a CoTe//AC asymmetric supercapacitor using a redox additive aqueous electrolyte

“…The capacitance retention rate of ASC containing redox additive was distinctly lower than those without K 4 Fe(CN) 6 , which could be attributed to the reduction of the activity of the redox additive in the redox process. 25,26 This could be veried by rate capability of ASCs with different electrolyte at different current densities. Fig.…”

Electrochemical Supercapacitors: From Mechanism Understanding to Multifunctional Applications

“…[ 13 ] Similarly, we have investigated the k eff values of carbon nanotubes/hydroquinone and reduced graphene oxide/hydroquinone interfaces as quantified by SECM in feedback mode, providing further understanding for redox‐active electrolyte SCs. [ 52 ] Through SECM mapping, Sapati et al. also verified the facilitated charge transfer to UME tip (biased at 0.4 V) when the electrochemically deposited MnO 2 is biased at −0.2 V. [ 35 ]…”

Development of a Novel Bio‐based Redox Electrolyte using Pivalic Acid and Ascorbic Acid for the Activated Carbon‐based Supercapacitor Fabrication

“…To achieve high energy density supercapacitors, redox‐active electrolytes containing a redox pair in a supporting electrolyte can be considered very promising. Recently, the introduction of redox mediators into electrolytes has become an effective method to improve the overall performance of supercapacitors [24–28] . Several redox couples, such as potassium iodide, [29] hydroquinone, [30] cupric chloride, [31] and potassium ferricyanide [32] incorporated in aqueous electrolytes, have resulted in a significant improvement in the performance of supercapacitors.…”

“…Recently, the introduction of redox mediators into electrolytes has become an effective method to improve the overall performance of supercapacitors. [24][25][26][27][28] Several redox couples, such as potassium iodide, [29] hydroquinone, [30] cupric chloride, [31] and potassium ferricyanide [32] incorporated in aqueous electrolytes, have resulted in a significant improvement in the performance of supercapacitors. Additionally, redox couples can easily penetrate the micro-and mesopores of an electrode material because they have a very small ionic size.…”