Pseudo-Capacitive and Electrocatalytic Properties of Electrochemically Modified Graphite Electrode in Different Solutions

Abstract

A graphite electrode (GE) was electrochemically modified by recurrent galvanic pulses. The pseudo-capacitive behavior in acidic and neutral solutions and the electrocatalytic property in HCl and HNO3 solutions of the modified graphite electrode (MGE) were evaluated by cyclic voltammetry (CV). We found that the MGE exhibited a considerable pseudo-capacitance (the specific capacitance was high up to 1.730 F·cm - 2 ) in H2SO4 solution and excellent pseudo-capacitive behavior was obtained in HCl solution as well except for a narrow potential window. This was due to the excellent electrocatalytic activity of the MGE toward the chlorine evolution reaction (the onset potential of chlorine evolution was negatively shifted 238 mV). However, the MGE showed no pseudo-capacitive behavior in HNO3 solution but did show electrocatalytic activity toward the reduction of nitric acid. Compared with the pseudo-capacitive behavior in acidic solutions, the potential window of the MGE in neutral solution was substantially broadened and its energy density improved greatly eventually even though the corresponding peak current density decreased.