Quantitative assessment of hysteresis in voltammetric curves of electrochemical capacitors

Abstract

A family of coefficients for quantitative assessment of hysteresis in cyclic voltammetric (CV) curves of electrochemical capacitors and of electrodes for electrochemical capacitors has been defined. Hysteresis index 1 (HI1) is based on the maximum in the difference in current measured at the same potential in ascending and descending branch of CV curve, and HI2 is based on the average difference in current measured at the same potential in ascending and descending branch of CV curve. The values of HI1 and HI2 range from 0 (no hysteresis) to 1 for an ideal capacitor. CV curves of two commercially available electrochemical capacitors over a potential range 0-1500 mV at scan rate of 5 mV/s showed HI1 of 0.94 and 0.97 and HI2 of 0.77 and 0.83, respectively. At the same experimental conditions, a series of 52 home made electrochemical capacitors showed HI1 up to 0.7 and HI2 up to 0.55. HI1 and HI2 measured at constant scan rate (5, 20 or 50 mV/s) in that series of capacitors showed a correlation coefficient >0.98 while HI1 and HI2 measured at different scan rates showed limited correlation. 98 CV curves of electrochemical capacitors and of electrodes for electrochemical capacitors from literature, obtained at various conditions show HI1 from 0.42 to 1, HI2 from 0.27 to 0.97, and a correlation coefficient of 0.90 between HI1 and HI2.

Tuning of Capacitance Behavior of NiO Using Anionic, Cationic, and Nonionic Surfactants by Hydrothermal Synthesis

“…Figure shows a set of cyclic voltammograms (CVs) recorded at a scan rate of 5 mV s −1 for NiO electrodes prepared with different surfactants. The shapes of the CV curves reveal that the charge-storage mechanism is very different from that of the electric double-layer capacitance, which is normally close to an ideal rectangular shape. , For all three NiO systems, the electrochemical redox peaks have been observed in the potential range of 0.25−0.55 V versus Hg/HgO. These peaks are attributable to quasi-reversible redox processes occurring on the surface of the NiO electrodes during the potential sweep according to the equation , Ni O + OH − ⇄ discharge charge Ni O O H + e − …”

“…The shapes of the CV curves reveal that the charge-storage mechanism is very different from that of the electric double-layer capacitance, which is normally close to an ideal rectangular shape. 1,47 For all three NiO systems, the electrochemical redox peaks have been observed in the potential range of 0.25-0.55 V versus Hg/HgO. These peaks are attributable to quasi-reversible redox processes occurring on the surface of the NiO electrodes during the potential sweep according to the equation 13,35 The anodic peak A (positive current density) (Figure 5) is due to the oxidation of NiO to NiOOH, and the cathodic peak C (negative current density) is for the reverse process, which is a signature of pseudocapacitance.…”

Effects of Carbon Nanotube Grafting on the Performance of Electric Double Layer Capacitors

“…Although the growth of CNTs does not change the surface areas, some of surface functionalities were removed during the growth at 800 °C. Also, the removal is more severe when there was no NH 3 addition. , The removal of the surface functionalities results in reduced capacitances, as shown in Figure a. This is attributed to the disappearance of and reduced pseudocapacitance for the ACC/CNT-0 and the ACC/CNT-1 EDLCs, respectively, at the lower scan rates.…”

Hysteretic behavior of bladder afferent neurons in response to changes in bladder pressure

“…Furthermore, if both Hmax and Hmean are large and the ratio of Hmax/Hmean is close to 1, this in general reflects more hysteresis in the system and larger, more uniform loops. Higher ratios of Hmax/Hmean indicate more peculiar loops [ 32 ] and more variability in the loops between cycles.…”

“…Hysteresis in the bladder pressure-firing rate relationship was calculated during bladder contractions using a method derived from Kosmulski et al [ 32 ] for electrochemical capacitors. Sets of three contractions (pressure change ≥ 10 cmH 2 O, stratified by 25 % intervals of the leak volume for slow fill trials) were used for hysteresis calculations (Fig.…”