Papers by Keyword: Electro-Catalysis

Abstract: In order to enhance catalytic properties of palladium or gold/palladium alloy on polyaniline surface, highly pure PANI nanofibers doped with phosphoric acid were synthesized via chemical self-assembled method. Its general morphology was observed by scanning electron microscopy analysis. The deposition of palladium or gold/palladium alloy on PANI nanofibers was accomplished through reducing reaction of PdCl₂ or PdCl₂/HAuCl₄ in aqueous solution by NaBH₄. Pd/PANI nanofibers or Au/Pd/PANI nanofibers have been evaluated for catalytic activity toward formic acid oxidation reaction. Palladium/PANI nanofibers or palladium/gold/PANI nanofibers on glass carbon electrodes exhibit effective electro-catalytic activity since the PANI nanofibers play excellent promoting role.

Abstract: The field of application of electrochemical analysis has been significantly widened after modified electrodes appeared. Metallic nanoparticles are ones of the most common used modifiers of the electrode surface to increase the sensitivity and selectivity of the analysis. Increasing of selectivity is extremely important in cases when two or more analyts have electro-chemical signals at nearly the same values of electrode potential. Dopamine and ascorbic acid are an example of such case. In present work Au, Pt, Pd, and Ni “pure” nanoparticles obtained by laser ablation without stabilizing agents were used to modify the surface of a glassy carbon electrode. Modified electrodes were tested in solutions of ascorbic acid and dopamine at their simultaneous electro-oxidation. It was shown that Au, Pt, and Ni nanoparticles on the electrode surface increase the selectivity of analysis giving two separate peaks of analyts.

Abstract: In this paper nanotube TiO₂ coating as an interlayer was produced on Ti substrate and the performances of the Ti/nanotube TiO₂/Sb-SnO₂ electrodes were investigated. It is shown that the microstructure of the nanotubes changes with the anodic oxidation voltage and time, and the introduction of the nanotube TiO₂ in the electrodes gives rise to both the oxygen evolution potential and the accelerated life of the electrodes.

Abstract: Oxidation of nitenpyram in aqueous media by electro-Fenton process using carbon/polytetrafluoroethylene (C/PTFE) O2-fed cathode has been studied in this article. ABO3 perovskite was used in electrode as catalyst of improving Fenton reaction efficiency. And the parameters for nitenpyram degradation with the electrode were determined by Central Composite Design-Response Surface Methodology. Current intensity 0.35A and pH 3.34 provided the optimum catalytic degradation. Furthermore, the main degradation intermediates formed during electro-Fenton oxidation treatment were studied with liquid chromatography and mass spectroscopy (LC-MS) method. The main aromatic intermediates of electro-Fenton reaction were allowed to compose a complete mineralization pathway.

Abstract: The Ti/SnO₂-Sb electrode with/without Er were manufactured by Pechini’s method. The electrodes were characterized using SEM, EDS, XRD, FT-IR, the oxygen evolution potential test and their electro-catalytic abilities were evaluated though nitenpyram degradation. XRD and FT-IR results showed that the structure of the electrodes were Sn-base sosoloid without Er and Sb phases. The Er³⁺ iron entering the unit cell of SnO₂ (Sn⁴⁺) could cause the grain refinement, the surface enrichment of Sb and Er, stronger water absorbability, and higher anode potential. These consequently generated more active sites and less oxygen vacancies on the anode surface, leading the improving of the electro-catalytic performance. The grain refinement mechanism for Er doping may be ascribed to the increase of the surface composition supercooling, the acceleration of the SnO₂ generation rate, and the restrain of its growth rate.

Abstract: In this work, F-Sb codoped SnO₂ film electrode material has been prepared and used as an anode on titanium (Ti) substrate for degradation of methyl orange. The emphasis is laid on the effect of univalent cations fluoride doped during preparation of F-Sn codoped SnO₂ composites by sol gel method. The facts show that univalent cations fluoride could affects the electro-catalytic degradation rate of methyl orange by F-Sb codoped composite film on the Ti electrode. A promotion to the degradation rates of methyl orange could be observed when KF or NH₄F was used as codopant but other fluoride codopant such as LiF, NaF or HF could slow the methyl orange degradation. X-ray diffraction (XRD) and x-ray photo-electron spectroscopy (XPS) were used to study structures and composition of the anode surface.

Abstract: Nanocristalline TiO₂ obtained by a facile and environment-friendly sonochemical method was subjected to thermal treatment in the temperature range of 400-900 °C in order to produce variable anatase-rutile phases ratio. The relationship between the optical bandgap and the electrochemical behavior was studied. All the stages of phase transformation of the as-prepared sample such as: nucleation, growth and coarsening were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that phase transformation mechanism stems from the redistribution of energy in the system and a critical particle size. On the other hand, the samples were characterized by UV-vis spectroscopy for the bandgap studies. The optical band gap of as-prepared sample increases to 3.31 eV with respect to 3.20 eV for bulk-anatase. This expansion could be attributed to quantum size effect. The i-E characteristics of samples with variable anatase-rutile ratio were obtained using cyclic voltammetry technique in a 0.5 M H₂SO₄ solution at room temperature. The foremost charge magnitude was obtained when anatase had a critical size of 17 nm. Analyzing both particle size for anatase and rutile, we observed that when rutile is the dominating phase and its size difference larger in 35% than anatase, the current reaches its minimum values. Based on electrochemical results, the optimal particle size and content phases control are important in order to obtain an increase in the electrochemical performance in the Hydrogen Evolution Reaction (HER) zone

Abstract: The Ru/C nanocomposites with loading of 20wt% were prepared by ethylene glycol in the presence of XC-72. Carbon-supported Ru nanoparticles were decorated with Pt by spontaneous deposition method after Ru surface oxides were reduced in the hydrogen atmosphere at 180 for 2h. TEM indicated that the average particle size of catalyst was about 4nm with excellent dispersion and the XRD analyzing results showed that Pt had decorated on surface of Ru. The anti-poisoning ability was studied by pre-adsorbing CO striping voltammetric curves in 0.1M HClO4. Catalytic activities of the prepared Pt/Ru/C were studied by cyclic voltammetry in a solution of 0.5 mol/L CH3OH + 0.1 mol/L HClO4. The results showed that the oxidation current density was far more than 60wt% RuPt/C (E-TEK) and 20wt% Pt/C (Johnson Matthey). At the same time, the study also showed that the prepared catalyst not only had a higher catalytic activity to methanol, but also had lower Pt loading.

Abstract: The Platinum catalysts on the carbon nanotubes(CNTs) supports of various diameters were prepared by wet impregnation method using H2PtCl6 precursor. The samples using 100nm, 15~20nm, 10~15nm and 5~10nm diameters of CNTs and carbon nanofibers(CNFs) are named Pt/t- CNFs, Pt/MWNTs20, Pt/MWNTs10 and Pt/MWNTs5, respectively. The effects of CNTs diameter on the Pt particle size and distribution were investigated by the means of powder XRD and TEM observation. In addition, the electro-catalytic characteristics for methanol electro-oxidation were estimated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The average size of Pt particles increases as follows; Pt/MWNTs10 < Pt/MWNTs5 < Pt/MWNTs20 < Pt/t-CNFs. The electro-catalytic characteristics of Pt/MWNTs10 and Pt/MWNTs20 are found to be superior in comparison with the others. For preparation of the most effective supported Pt catalyst, the optimum diameter of CNTs support in the range of 10-20nm, is needed.