Font Size: a A A

Electrochemical Surface Processes Investigated By Using In Situ Vibrational Spectroscopies And Scanning Tunneling Microscope

Posted on:2001-12-29Degree:DoctorType:Dissertation
Country:ChinaCandidate:X Y XiaoFull Text:PDF
GTID:1101360062475600Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
The introduction of in situ surface techniques enables the interpretation of electrochemical surface processes at a molecular or atomic level. Among them in situ Fourier transform infrared spectroscopy (FTIRS) and in situ electrochemical scanning tunneling microscope (EC-STM) have found many advantages in disclosing the nature and kinetics of the adsorption processes through the identification of the molecular structure and the surface structure in real space, respectively.In this work, some fundamental surface processes were investigated as follows: (1) Studies of interaction between amino acids and Pt, Au polycrystalline and single crystal electrodes. These studies can provide fundamental information of the adsorption properties of biochemical molecules such as peptide, protein, etc., and on the other hand, these molecules can be used as model molecules in studying the characteristics among the several selected functional groups. (2) Study of potential dependent orientation of adsorbed p-nitrobenzoic acid on Au surface, which is essential in understanding the surface process and the coordination properties of adsorption of PNBA. (3) copper deposition on Pt single crystal electrodes. By using copper deposition as a model, the influence of the adsorbed anions, the deposition processes, and the internal structure of the deposits were investigated. (4) fabrication of nanostructures by STM tip induced surface alloying process. To obtain a clear and understandable results, in situ surface techniques such as FTIRS, STM, SERS, EQCM, were employed.Ph.D. Dissertation of Xiamen University Abstract in English The main results and conclusions are summarized as follows:[1] In chapter 3, we presented studies of CO and CIST adsorption and oxidation in alkaline solution electrochemically and spectroelectrochemically. The "bridge" (CO)s is well identified by using AIREs, which shows abnormal IR effects of adsorbed species on the nm-Pt/GC electrode. The coadsorption of "linear" (CO) L and "bridge" (CO)s, was observed in the potential region of CO adsorption from -0.9 to -0.5 V. Upon CO oxidation, the total CO coverage decreases together with the increase of the ratio of (CO) L /(CO)B, indicating that on one hand (CO)e is more active than (CO) L, and on the other hand the phase transition from "linear" (CO) L to "bridge" (CO)s exits at a low reaction rate. The CO oxidation is significantly influenced by the potential dependent electrochemical formation of adsorbed Pt-OH. However, it is also sensitive to the solution species OH" because the oxidation already starts in the hydrogen adsorption region.Cyanide is very strongly adsorbed on the Pt surface in the potential region of -0.9 to 0.0 V. The potential dependence of the frequency of adsorbed CN" is in a good agreement with the electrochemical Stark effect, however, yielding three different values of Stark effect upon different potential regions. The intensity of CN" decreases with the increase of potential. The characteristic potentials of -0.7 and -0.4 V are corresponding to the potential of hydrogen desorption and the potential of zero charge of Pt surface, as well as the beginning of adsorption of oxygenated species. The variation of IR spectral features can be interpreted as a phase transition of adsorbed CN" together with a lateral influence by co-adsorbed hydrogen and oxygenated species (normally, Pt-OH).Ph.D. Dissertation of Xiamen University Abstract in English[2] In chapter. 4 and chapter 5, the adsorption and electrochemical oxidation of amino acids ( glycine (CH2(NH2)COOH), serine (CH2(OH)CH(NH2)COOH) and threonine( CH3CH(OH)CH(NH2)COOH )) on platinum and gold poly- or single crystal (111) electrodes were investigated by combining cyclic voltammetry and in situ vibrational spectroscopies (FTIRS and Raman spectroscopy). It can be concluded that the electrochemical oxidation of these amino acids leads to the formation of adsorbed cyanide. The inhibition of hydrogen adsorption and self-inh...
Keywords/Search Tags:Pt,Au Poly, Single Crystal Electrodes, Amino Acids, Adsorption, Copper Deposition, in situ Vibrational Spectroscopies, Electrochemical Scanning Tunneling Microscope
PDF Full Text Request
Related items