Electrochemically Activated Glassy Carbon Electrode And Its Application In Electroanalysis

Glassy carbon (GC) is the most frequently used carbon material electrode in electrochemistry. Its surface has diverse character varying with the experimental condition. Unfortunately, varieties effects of electrode itself on the research result often were neglected or not deeply explored in most of publications involving GC electrode. Consequently, it increases the possibility that misunderstanding might exist in the corresponding conclusion, which is one of the most important problems for the application of GC electrode in electrochemical study. The clear understanding of the relationship between the character and the electrode interface is not only the guarantee to obtain a correct research conclusion, but also is the precondition to extend the application of GC electrode.In this thesis, two electrochemical activation methods and two activation solution were used to obtain four types of the activated GC electrodes. Effects of electrochemical activation procedure on the structure, the size, the distribution and the type of electron transfer site on electrode surface have been investigated. Application of electrochemical activation GC electrode has been exploited in electroanalysis of metal ions. Meanwhile, the essence structure and character of electron transfer site of sp2 hybridized carbon material have been explored.The redox behaviors of copper species at electrochemically activated GC electrodes have been investigated in aqueous solutions containing chloride anions. Experimental results showed that the voltammetric responses of copper species were influenced by the electrochemical activation means employed. Abnormal copper stripping was observed at electrodes obtained by cyclic polarization. Experimental results demonstrated that abnormal copper stripping was caused by low distribution density of electron transfer sites for the early nucleation of metallic copper in the presence of chloride anion, and was not resulted from the new characters of adsorption and cation exchange. Electrochemical activation was an erosion process of the interwoven graphitic crystallites of glassy carbon. Cyclic polarization might cause changes in the surface structure of graphitic crystallites throughout, while polishing or potentiostatic polarization means did not. Cyclic polarization was considered a weak activation means not able to remove carbon oxide effectively when compared with potentiostatic activation. Oxygen-containing groups produced by cyclic polarization might accumulate at the whole graphitic crystallite surface and penetrate the crystallite to some extent with increasing extent of polarization. The accumulation of oxygen-containing functionalities might cause decreases in the distribution density of electron transfer sites. On the other hand, potentiostatic activation was an intense erosion means capable of removing the excrescent carbon oxide at the graphitic crystallite surface to create larger void space without changing the basic surface structure of graphitic crystalline.The surface characters of GC electrochemically activated glassy carbon electrode also were investigated on the base of Vitamin C (AA) and dopamine (DA) probe, and were compared with that of carbon nano tube and graphitic powder. Experimental results showed that the voltammetric response of AA species was more sensitively responded for the change of electrode surface than that of DA. It reflected that the electrode surface obtained by potentiostatic activation in H2SO4 was similar as that of single wall carbon tube (SWNT), but different from that of multi wall carbon tube (MWNT) and other three types of the activated electrode. Potentiostatic activation in H2SO4 might oxidize the graphitic crystallite of nanometer into smaller particle, so that produce some of oxide graphitic pieces close to monolayer scattering at the activated surface.The application of electrochemically activated GC has been primarily explored for in-situ preparing of bismuth film electrodes (BiFEs) to analyze Pb2+ and Cd2+. Experimental results showed that the presence of chloride ion would effectively improve the deposition of metal (bi, pb and cd), and largely increase the square wave anodic stropping peak height of metal depositing. Using of HCl solution substituting acetate buffer as analytical solution, not only would reproducibly renew the electrode surface with an electrochemical clear procedure, but also could eliminate effect of hydrolysis of bi species. At the same time, the square wave anodic stropping method of BiFEs could be extended to analyze sample containing chloride anion, such as sea water. Under a simple experimental conditions, the newly developed method involving the activated GC and HCl solution could more sensitively analyze Pb2+ and Cd2+ than tradition one, especially for Cd2+. 240 seconds of accumulation resulted in liner response range within 0.01-0.1μmol/L with response slope of 125 A?L/mol for Pb2+ and 98 A?L/mol for Cd2+. Detection limit was down to 1 and 3 nmol/L .