摘要
对碳毡表面HNO_3化学改性引起电极性能的变化进行较详细研究。物理分析数据表明,由于HNO_3氧化处理,碳毡表面亲水性含氧官能团含量增加及HNO_3分子易嵌入并吸引高温碳毡石墨层状结构中的电子使空穴增多,电极表面浸润性和导电性明显提高。碳毡比表面也因HNO_3腐蚀作用有所增加。另外,循环伏安分析结果指出,在表面改性电极上Cr^(3+)/Cr^(2+)及Fe^(3+)/Fe^(2+)反应电化学活性增强,不仅峰值电流I_(pa)、I_(pa)随HNO_3氧化时间增长明显加大,而且峰电位差△Ep(=E_(pa)-E_(pc))变小,反应更趋可逆。还因为催化剂Pb沉积量增加而提高了其催化活性,经HNO_3氧化处理后的碳毡表面更利于Cr^(3+)/Cr_(2+)反应进行,其I_(pa)、I_(pc)值的增加明显高于Fe^(3+)/Fe^(2+)反应。
Carbon felt is a preferable electrode material in new type electrochemical energy storage systems because of its large physical strength and surface area, high conductivity, and good heat and corrosion resistance. To improve the properties of carbon felt electrodes by chemisorption of oxygen and formation of surface functional groups on carbon surfaces is an interesting subject. In this study chemical oxidation by HNO3 is used to modify the carbon felt surface. The physical and chemical consequences of HNO3 treatment were investigated in detail.
Experimental results indicated that formation of large amount of hydrophilic oxygen-containing functional groups ( - COOH and C -OH)due to HNO3 treatment leads to great improvement in the wettability of carbon felt surface, especially dramatic decrease of the surface contact angle with water (from 76. 5°to 39. 5°). Since high temperature processing carbon felt (≥1700℃) has graphite layer structure and weak Van Der Waals combination between layers, HNO3 molecules are easy to be introduced into layers and draw electrons of graphite to increase the carbon felt's conductivity. The corrosion of HNO3 also causes the increase of BET surface area of carbon felt.
In a redox flow cell, Cr3+/Cr2+ and Fe3+/Fe2+ redox reaction are carried out on negative and positive carbon felt electrodes, respectively. Au-Pb was found to be a suitable catalyst for reaction. It was prepared by the thermal decomposition of a Au salt followed by electrodeposition of Pb on the carbon felt electrode. The cyclic voltammetric results indicated that the peak currents, Ipa and Ipc of both Cr3+/Cr2+and Fe3+/Fe2+reaction are enhanced afttr HNO3 treatment. The peak potential difference ΔEp(=Epa-Epc) decreases after HNO3 treatment, implying the better reaction reversibility. Moreover, as the amount of deposited Pb and its catalytic activity increase, modified carbon felt surface is more beneficial for Cr3+/Cr2+ reaction. Therefore, increment value of Ipa and Ipc for Cr3+/ Cr2+reaction is higher than that for Fe3+/Fe2+reaction. It is concluded that HNO3 chemical modification can enhance the electrochemical activities of carbon, felt electrodes greatly.
出处
《分子催化》
EI
CAS
CSCD
1992年第4期297-302,共6页
Journal of Molecular Catalysis(China)
基金
国家自然科学基金资助课题
关键词
碳毡
电极
硝酸
电催化
Carbon felt electrodes, Carbon felt surface, NHO3, Electro-catalysis.
