Papers by Keyword: Electrocatalysis

Abstract: Nano-particles of platinum were prepared using Metal Organic Chemical Vapor Deposition (MOCVD) technique and supported in a carbon nano-tube (CNT) matrix in order to obtain different atomic relationship: Pt (1%)/CNT, Pt (5%)/CNT and Pt (15%)/CNT. The as-prepared Pt/CNT was deposited on a glassy carbon (GC) electrode. Nitrate electro-reduction reaction (NER) was used as a probe to evaluate their catalytic activity. According to XRD analysis the particle size was determined as 15, 13 and 12 nm for Pt (15%)/CNT, Pt (5%)/CNT and Pt (1%)/CNT, respectively. Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) confirmed the presence of nano-tubes and the platinum atomic ratio in each sample. The adsorption-desorption region related to the Hydrogen Evolution Reaction (HER) was evaluated. The charge obtained (Q/μC) followed the order Pt(15%)/CNT>Pt(5%)/CNT>Pt(1%)/CNT, in agreement with platinum content. The i-E profiles at nitrate-containing solutions showed a redox process corresponding to the NO₃^- reduction. Cyclic voltammetry (CV) coupled with rotating disk electrode (RDE) technique revealed that the NER is affected by the rotation rate, an indication of a strong competition of nitrate ion and protons at the electrode interface. Studies as a function of NO₃^- concentration (0.001, 0.01, 0.1 and 1.0M) were also carried out. The electrical current attributed to nitrate reduction increased, for all samples, as a function of concentration. Nevertheless, this current magnitude is not severely affected by the content of platinum-nanoparticles. These results have been discussed in terms of local disorders due to particles size-distribution as well as the support matrix geometry (SMG).

Abstract: A new electrochemical biosensor based on the immobilization of horseradish peroxidase(HRP) on TiO₂ nanoneedles modified electrodes has been fabricated. The direct electrochemical response of HRP immobilized on the modified electrode was dramatically enhanced. The immobilized HRP displayed a couple of stable and well-defined redox peaks with a formal potential of -0.379 V (vs. SCE). The HRP/TiO₂ nanoneedles modified electrode exhibited a remarkable electrocatalytic activity toward the oxidation of H₂O₂. The amperometric response to H₂O₂ showed a linear range of 4–700μmol/L, with the calculated detection limit of 0.78 μmol/L at a signal-to-noise ratio of three. The modified electrode displayed an acceptable reproducibility and good stability. The new HRP/TiO₂ nanoneedles matrix is expected to have wide applications for enzymes and proteins immobilization and direct electron transfer study and opened a way for low conductivity electrode biosensors.

Abstract: A facile electrochemical approach was developed for controllable synthesis of ytterbium hexacyanoferrate(II) (YbHCF(II)) carambolalike microparticles. The prepared samples were characterized by XRD, EDS and SEM techniques. The composition of YbHCF(II) sample could be assigned to be KYb[Fe(CN)₆]∙xH₂O. By controlling the synthetic conditions, such as applied potential and deposition time, the size and surface morphology of the synthesized materials could be well controlled. The modified Au electrode by YbHCF(II) carambolalike microparticles possesses prominent electrocatalytic activity toward the reduction of hydrogen peroxide.

Abstract: A novel method of cellulose degradation is investigated in this paper. In this work, a three-electrode system, which contains a Pb/PbO₂ anode, two copper cathodes and a reference saturated calomel electrode (SCE), is applied to electrocatalytic degradation of cellulose. The composition of the products in filtrate is characterized by phenol-sulfuric acid method, NMR and GC-MS. In addition, the solid sample is analyzed via Ubbelohde capillary viscometer and FT-IR spectra. The results suggest that it is effective to convert cellulose to soluble sugar, 5-hydroxymethylfurfural (5-HMF) and other products by electrocatalytic method. The reaction mechanism of cellulose degradation is also discussed.

Abstract: With mixed rare earth (La, Ce, Nd) doping Ti/TiO₂ electrode for the anode, degradation situation of oilfield wastewater was studied. The results showed that electrocatalysis technology excels at treating oilfield wastewater. Electrocatalytic oxidation reaction kinetic equation: A_t=A₀exp(-7.02×10^-7D^-1.42M^-1.66U^3.40t).

Abstract: The novel electrochemical membrane reactor for wastewater treatment was designed and introduced. As the key part of the electromembrane reactor, the tubular membrane electrode was prepared and researched. The tubular inorganic ceramic membrane was endowed with electroconductivity by the deposition of pyrolytic carbon from propylene by chemical vapor deposition. The electrocatalytic property of the membrane electrode was realized through dip-coating with chloroplatinic acid solution, drying and hydrogen reduction in order that the electrocatalyst of reduced platinum can be supported. The SEM characterization and water flux test of the membrane electrode show that membrane separation and electrocatalysis can be integrated together.

Abstract: The anodic electrodeposition of polyaniline (PANI) on Pb substrate was performed by both potentiostatic and galvanostatic method. Influences of the applied potential and current density on the formation of PANI were investigated. The electrocatalytic effect of Pb electrode modified by PANI on the oxygen evolution reaction (OER) in sulfuric acid was examined via anodic polarization measurements. The results indicated that a significantly enhanced catalytic activity was obtained on Pb electrodes modified by PANI. The overpotential for OER drops 0.14V~0.42V and the exchange current density rises by one to three orders of magnitude compared to the blank Pb electrode. As a new kind of OER anodes in acidic electrolytes, the Pb electrode coated by PANI shows a potential application prospect in the electrowinning of non-ferrous metals.

Abstract: Pt/rare-earth cathode catalysts were synthesized by the alcohol-reduction process and its structure was investigated by transmission electron microscopy (TEM), energy dispersive analyses (EDS), X-ray Diffraction (XRD). The electrochemical behavior of the cathode catalyst was analyzed by cyclic voltammetry (CV) chronoamperommetry (CA).

Abstract: Potentiodynamic polarization of a mechanically polished titanium electrode in a diluted solution of Rhodium(III) chloride in 0.1 M perchloric acid was performed, resulting in simultaneous formation of both Rh and TiO2 films. The morphology of obtained Rh/TiO2 composite film followed the morphology of titanium support, as evidenced by SEM technique. This composite surface was examined by cyclic voltammetry in both acidic and alkaline solutions, in the potential region of both hydrogen and oxygen underpotential deposition. The charge related to hydrogen underpotential deposition corresponded to a surface roughness of 43. As a consequence of high surface roughness, the diffusion current of oxygen reduction in an oxygen saturated 0.1 M NaOH solution, measured by voltammetry on rotating disc electrode, was found to be comparable to the current of hydrogen underpotential deposition.

Abstract: Spontaneously-deposited Pd-black films were prepared on a Ni mesh. Characterization of the films morphology was performed by Scanning Electron Microscopy. Cyclic voltammetry in 0.1 M NaOH was used to characterize the voltammetric profile in the H-adsorption/absorption region. Contrasting to smooth Pd, the results revealed that the H-adsorption peak can be detected using this electrode. It was found that the displacement metal reaction leads to codeposition of Ni during the Pd-black film preparation. The ability of these electrodes to be used on the electrohydrogenation of organic molecules was evaluated using 3-buten-1-ol as a test molecule. It was also analysed the stability of the electrodes upon reusing the same electrode in repetitive electrolysis. It was concluded that the films present a very good catalytic activity to electrohydrogenation but show poor adherence to the substrate when are re-used.