电化学改性石墨电极在不同溶液中的准电容及电催化性能

通过循环电流阶跃方法制备电化学改性石墨电极(MGE), 用循环伏安(CV)法评价了MGE在酸性和中性溶液中的准电容特性, 并研究了其在HCl和HNO₃溶液中的电催化作用. 结果表明: 在酸性条件下, MGE在H₂SO₄溶液中具有佷好的准电容特性, 比电容高达1.730 F·cm^-2; 在HCl溶液中也具有很好的准电容特性, 且MGE对析氯反应具有一定的电催化活性(起始析氯电位负移238 mV), 使其电位窗变窄; 在HNO₃溶液中没有准电容特性, 而MGE对NO₃^-离子的还原反应具有极强的电催化能力. 当电介质由酸性变为中性时, 虽然其峰电流密度有所降低, 但电位窗大幅度增宽, 意味着MGE在中性体系中的能量密度比酸性体系会有较大的提高.

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

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.