关键词: 电化学改性石墨电极, 铁离子, 电催化, 电化学电容, 准电容

Abstract: The electrocatalytic performance and pseudocapacitive characteristics of a modified graphite electrode (MGE) with Fe³⁺/Fe²⁺ in H₂SO₄ solution were studied by cyclic voltammetry (CV), constant current charge-discharge measurements, and electrochemical impedance spectroscopy (EIS). The results showed that the MGE had high electrocatalytic activity and good reversible characteristics for the redox reaction of Fe³⁺/Fe²⁺ because of a large quantity of oxygen-containing functional groups on the MGE surface. The apparent area-specific capacitance of the MGE in 2.0 mol·L^-1 H₂SO₄ solution containing 0.5 mol·L^-1 Fe³⁺ and 0.5 mol·L^-1 Fe²⁺ reached 2.157 F·cm^-2, which was almost double that in 2.0 mol·L^-1 H₂SO₄ without Fe³⁺/ Fe²⁺ . Meanwhile, increasing the concentration of iron ions increased the capacitance of the MGE. The addition of Fe³⁺/Fe²⁺ made the charge-discharge curves more symmetric and change more slowly, which increases the charge-discharge time, and effectively improves the capacitive energy storage and high power performance for an electrochemical capacitor (EC). The obvious capacitive characteristics were confirmed by EIS, and are attributed to the oxygen-containing functional groups on the MGE and the Faraday redox reaction of Fe³⁺/Fe²⁺ in the thin electrolyte layer. Therefore, the oxygen-containing functional groups on the MGE surface and redox reaction of Fe³⁺/Fe²⁺ can be used together for energy storage and release.

Key words: Modified graphite electrode, Iron ion, Electrocatalysis, Electrochemical capacitor, Pseudo-capacitance