Electrocatalytic And Analytical Applications Of Chemically Modified Platinum Electrode Coated With The Hybrid-metallic Cyano-Bridged Mixed Coordination Polymer Containing Europium Or Neodymium Element

In the doctoral thesis, two kinds of platinum electrodes which were chemically modified with the hybrid-metallic cyano-bridged mixed coordination polymers containing the composition of the europium-glycine complex (Eu(Ⅲ)Gly)x) and the neodymium-phthalic acid complex (Nd(Ⅲ)(o-phth)x) were prepared respectively by electrodeposition methods. Furthermore, the electrocatalytic behavior of such a modified electrode was investigated and their characteristics in applications of analytical chemistry were explored. The main content of the paper is as follows:1. A platinum electrode modified with the Eu(Ⅲ)Gly)x-Fe-CrO42-coordination polymer was prepared successfully by electrodeposition methods. The scanning electron microscope (SEM), FT-IR, FT-Raman, and solid surface reflect fluorescence techniques were used to characterize properties of the modified material. The electrocatalytic oxidation behavior of tris(2,2'-bipyridyl)-ruthenium(II)(Ru(bpy)32+) was investigated in detail on the modified platinum electrode (Eu(Ⅲ)(Gly)x-Fe-CrO42-/Pt) by cyclic voltammetry (CV) and square wave voltammetry (SWV). In the electrolyte containing0.45mol/L potassium nitrate, Ru(bpy)32+exhibited the stable and good electrocatalytic oxidation characteristic on the Eu(Ⅲ)(Gly)x-Fe-CrO42-/Pt, and a linear relationship between the square wave peak current and Ru(bpy)32+concentration was shown in the range of0.001～1.0mmol/L. The catalytic oxidation efficiency of Ru(bpy)32+increased to3.5times on the modified platinum electrode comparing with its values on the bare platinum electrode. In addition, it was discovered that because of the enhancement of catalytic oxidation efficiency on the modified electrode surface, the total electrochemiluminescence intensity of Ru(bpy)32+system also increased under the same experimental condition. Based on the above evidences, a novel mechanism model was proposed to interpret the ECL behavior of Ru(bpy)32+system on the modified platinum electrode. As a possible analytical application for capillary electrophoresis coupled with end-column electrochemiluminescence detection, it was testified that when modified platinum electrode was used as a detector's working electrode, the sensitivity of CE-ECL for determining the probe samples containing tripropylamine (TrPA) and triethylamine (TEA) was positively improved by about one order of magnitude.2. A novel modified platinum electrode (Nd(Ⅲ)(o-phth)x-Fe-MoO42-/Pt) was prepared by electrodeposition methods. The scanning electron microscope (SEM), FT-IR, FT-Raman, and X-ray powder diffraction (XRD) techniques were used to characterize properties of the modified material. The electrocatalytic activity and CO-poisoning tolerance of the modified electrode had been studied on the decorated polycrystalline platinum surface for ethanol electrooxidation. In addition, the electrocatalytic oxidation of ethanol was studied in detail by using cyclic voltammetry (CV) and chronoamperometry (CA) in a weakly acidic condition, and the presence of five distinct current peaks related to the ethanol electrooxidation process was observed. From the voltammetric data analysis, the kinetic behavior of backward oxidation peak in negative-going sweep was considered to be a diffusion-controlled electrochemical process. Therefore, the nature of backward oxidation peak was reasonably attributed to the plentiful products of acetaldehyde via a one-step concerted dehydrogenation pathway of ethanol. These results implied that the electrooxidation of ethanol possibly had different dehydrogenation pathways on the decorated platinum electrode comparing with normal ones. Based on the particular experimental evidences, a new dehydrogenation model was proposed to explain preliminarily the mechanism of ethanol electrooxidation.3. A composite modified platinum electrode (Pt-particles/Nd(Ⅲ)(o-phth)x-Fe-MoO42-/Pt) was successfully prepared by the two-step electrodeposition method. The voltammetric behavior of methanol on the Pt-particle/Nd(Ⅲ)(o-phth)x-Fe-MoO42-/Pt composite modified electrode was studied by cyclic voltammetry (CV) and chronoamperometry (CA). The experimental results showed that because of the good dispersive uniformity and the feasible carrying capacity of Pt-particles on the modified electrode substrate, the high efficient electrocatalytic activity for methanol oxidation was available at the composite modified electrode. Under a weakly acidic condition, the current density of main oxidation peak in positive-going sweep for0.25mol/L methanol could achieve up to120mA/cm2. Furthermore, from the analysis to voltammetric data, the nature of four voltammetric peaks relating to the oxidation reaction of methanol was revealed respectively with a reasonable explanation. Therefore, it was inferred that the dehydrogenation mechanism of methanol on Pt-particles/Nd(Ⅲ)(o-phth)x-Fe-MoO42-/Pt electrode would undergo a multi-step single electron transfer process which was promoted by PtOH active intermediates.