Humic acids as pseudocapacitive electrolyte additive for electrochemical double layer capacitors

• Humic acids (HA) were applied for the first time as electrolyte additive for EDLC.
• Capacitances consistently rise with HA addition to 6 M KOH with maximum at 5 wt.%.
• Positive effect of humic acids has been ascribed to pseudocapacitive phenomena.
• Humic acids are described as low-cost, non-toxic and “green” electrolyte component.

Novel electrolyte additive for electrochemical capacitors has been reported. It has been demonstrated for the first time that addition of humic acids (HA) to KOH-based electrolyte significantly increases capacitance of symmetrical capacitors with electrodes made of activated carbon. Specific capacitances determined by means of galvanostatic charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy consistently showed increases for HA concentrations ranging from 2% w/w up to saturated solution with maximum positive effect observed for 5% w/w of the additive. The capacitance increase has been attributed to complex faradaic processes involving oxygen-containing groups of HA molecules. Due to abundant resources, low cost and easy processability the reported solution can find application in electrochemical capacitor technologies.

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