Study Of Adsorption And Oxidation Of Serine On Pt And Pt Single Crystal Electrodes In Neutral Solutions Using CV And In Situ FTIRS

The adsorption and oxidation of serine on Pt poly and single crystal electrodes in neutral solutions were studied using cyclic voltammetry (CV) and in situ FTIR spectroscopy (in situ FTIRS). The main results are summarized below.1. The FTIRS results demonstrated that the dissociative adsorption of serine on Pt surface can occur in low potential region. The chemisorbed species were identified as adsorbed CO(CO_L,CO_B)and CN^- species. IR band at 2343 cm^-1 is ascribed to CO₂, which implies the cleavage of the C-C bond of serine during its dissociative adsorption. It has determined that the cyanide was strongly adsorbed on electrode surface in a wide potential region below 0.7V (vs.SCE) and inhibited the oxidation of serine. At higher potentials, the serine molecules could be oxidized directly to yield the main product CO₂ species. As the pH decreased in the spectroelectrochemical cell during serine reactions, the acidic serine species also detected. The present study revealed the interaction of serine with Pt electrode surface, and suggested a possible reaction mechanism of serine on Pt electrode in neutral solutions.2. It has demonstrated that the electrochemical reactivity of serine depends strongly on the concentration of H⁺ cation. The oxidation of oxidative dissociation adsorbates (ODA) yielded large current density in solution of higher pH value. This phenomenon could be ascribed the existence of different forms of serine molecule in different pH solutions, and also to concentration of OH^- anion.3. In neutral solutions, the oxidative dissociation of serine produced ODA that consisted of CO_L, CO_Må’ŒCN_ad^- on Pt(111) surface, while CO_L,CO_M and CN_ad^- on Pt(110) and Pt(100) surface as determined by in situ FTIR analysis. The CN_ad^- species are stable on Pt(111) and Pt(110) electrodes ,but can be oxidized successively when E_S>0.4V into cyanate (OCN^-) and CO₂ on the Pt(100) electrodes.4. The surface structure effects of Pt single crystal electrodes in oxidation of serine were studied. The adsorption and oxidative dissociation of serine are revealed to be surface structure sensitive in neutral solutions. The results of serine oxidation and adsorption on three low index and on a series of high index planes of Pt single crystal electrodes demonstrated that: larger peak current densities of ODA oxidation were observed on surfaces that contain mainly (100) and (111) surface sites, while smaller current densities were observed on surfaces of mainly (110) structure ; The oxidation of the ODA yielded sharp and narrow peak at high potentials on surfaces with (100) and (111) symmetry, however, on the surfaces containing mainly (110) structure the oxidation of the ODA was occurred in at relatively low potentials , illustrating a broad peak.The results obtained in this thesis have revealed the surface structure effects of Pt single crystal electrodes , and have thrown a light on elucidating the reaction mechanism of serine molecule on Pt surfaces at molecule level. The current studies are also of importance in applications of electrocatalysis, and bio-sensors.