Electrochemically active hydroquinone-based redox mediator for flexible energy storage system with improved charge storing ability

A Redox-Mediator-Integrated Flexible Micro-Supercapacitor with Improved Energy Storage Capability and Suppressed Self-Discharge Rate

“…The CV of the HQ-MSCs exhibited a pair of peaks at 0.15 V, which is a significant characteristic of the electrochemical multiple Faradaic redox reaction of the HQ-RMs during the charge/discharge cycles. The expected redox reactions of the HQ-RMs during the charge/discharge cycles are as follows (Figure 3b) [23,41,43,45]: hydroquinone (HQ) → benzoquinone (BQ) 2H + + 2e − (charge process) benzoquinone (BQ) 2H + + 2e − → hydroquinone (HQ) (discharge process) Furthermore, the CV curves of the HQ-MSCs showed similar shapes with increasing scan rates from 10 to 100 mV s −1 , indicating that the HQ-MSCs have good energy-storing kinetics and reversible capacitive behavior (Figure 3c). Especially, as indicated in Figure S3, at slow scan rates, all the possible ion adsorption and electrochemical reactions are maxi-mized on the surface within the given sweeping window (the clear redox pairs are detected).…”

“…Thus, it is expected that the HQ-MSCs will exhibit improved energy-storing properties owing to their unique structural/electrochemical features as follows: (1) the well-designed graphite-like carbon-based interdigitated electrodes with good electrical conductivity, which supports the fast electron pathway; (2) the large surface area by porous structures, which provide large electrolyte contact areas; and (3) the induction of additional Faradaic redox reactions using HQ-RMs, which induce improved energy storage properties, as shown in Figure 1e. There is synergistic electrochemical contribution on the surface of the carbon electrodes (both electrical double-layer capacitance and Faradaic redox reactions by the HQ-RMs) [42][43][44].…”

“…The CV of the HQ-MSCs exhibited a pair of peaks at 0.15 V, which is a significant characteristic of the electrochemical multiple Faradaic redox reaction of the HQ-RMs during the charge/discharge cycles. The expected redox reactions of the HQ-RMs during the charge/discharge cycles are as follows (Figure 3b) [23,41,43,45]: hydroquinone (HQ) → benzoquinone (BQ) 2H + + 2e − (charge process) benzoquinone (BQ) 2H + + 2e − → hydroquinone (HQ) (discharge process)…”

Surface Engineering of Carbon via Coupled Porosity Tuning and Heteroatom‐Doping for High‐Performance Flexible Fibrous Supercapacitors

“…In particular, the presence of oxygen-containing © 2021 Wiley-VCH GmbH functional groups can lead to the pseudocapacitive Faradaic reaction and, thus, enhance the specific capacitance. [14,18,20] The specific redox reaction is demonstrated by the cyclic voltammetry (CV) curves that were obtained using a threeelectrode system (Figure S4, Supporting Information), where the FFS-NFMCF exhibits the largest CV curve and the most distinct redox peak. Further, the CV curves obtained at scan rates of 0.5, 1.0, 3.0, and 5.0 mV s −1 (Figure 8b−d) clearly demonstrate the synergistic effects of porosity tuning and heteroatom codoping upon the overall energy storage mechanism.…”

“…In addition, the carbon fiber-based electrochemical double-layer capacitors (EDLCs) can better fulfill the requirements for a flexible energy storage system, including easy fabrication, high power density, and excellent long-term stability. [18][19][20] Moreover, the easy application of these advantages to wearable electronic devices makes the fibrous supercapacitor a desirable alternative to the conventional supercapacitor and LIB. Nevertheless, the fibrous supercapacitor suffers from severe problems due to the low specific surface area, limited electrical conductivity, and poor wettability of the carbon fiber electrode with the electrolyte, thus leading to a poor energy storage performance.…”