The anodic oxidation of copper in hydroxide solutions has been reexamined with the rotating ring and split‐ring disk techniques. A soluble Cu(III) species has been identified in the anodic region at the onset of oxygen evolution. This species has also been generated at gold rings from disk‐produced Cu(II). Passivation processes in the copper (I) and (II) oxidation regions have been analyzed by means of the corresponding ring currents.
Super-hydrophobic 3D SnO(2) flowers with nanoporous petals were produced from the 3D Sn nanoflowers using a controlled shape-preserving thermal oxidation process.
The influence of the iridium oxide thin film on the electrocatalytic properties of platinum nanoparticles was investigated using the electro-oxidation of methanol and CO as a probe. The presence of the IrO(2) thin film leads to the homogeneous dispersion of Pt nanoparticles. For comparison, polycrystalline platinum and Pt nanoparticles dispersed on a Ti substrate in the absence of an IrO(2) layer (Ti/Pt) were also investigated in this study. Inverted and enhanced CO bipolar peaks were observed using an in situ electrochemical Fourier transform infrared technique during the methanol oxidation on the Pt nanoparticles dispersed on a Ti substrate. Electrochemical impedance studies showed that the charge transfer resistance was significantly lower for the Ti/IrO(2)/Pt electrode compared with that of the massive Pt and Ti/Pt nanoparticles. The presence of the IrO(2) thin film not only greatly increases the active surface area but also promotes CO oxidation at a much lower electrode potential, thus, significantly enhancing the electrocatalytic activity of Pt nanoparticles toward methanol electro-oxidation.
The electrooxidation of sulfide on a microstructured oxide electrode Ti/Ta 2 O 5 -IrO 2 was studied using electrochemical methods such as cyclic voltammetry, differential capacity, galvanostatic measurements and electrochemical impedance spectroscopy (EIS). Sulfide and hydrosulfide can be oxidized to sulfur, polysulfides, and sulfate depending upon the electrode potential. Our surface analysis illustrates that the Ti/Ta 2 O 5 -IrO 2 electrode prepared in this study has a "cracked mud" structure with oxide particles sitting on the top of the electrode surface which have a particle size of around 100 nm. For the first time, two distinct galvanostatic potential oscillations, named as Oscillation A and Oscillation B, respectively, are observed during the electrooxidation of sulfide on an oxide electrode. The features of the potential oscillations strongly depend on the applied current densities. Oscillation A, located in the low current region, has larger amplitudes and much smaller frequencies than Oscillation B, which occurs in the high current region. Our EIS studies show that both Oscillation A and Oscillation B can be classified into HNDR (hidden negative differential resistance) oscillators with oxygen evolution involved. Oscillation A is caused by the variation of the S 2-/HSsurface concentration from the diffusion-limited depletion by oxidation and from the convection-induced replenishment by periodic oxygen evolution, while Oscillation B is due to the synergic effect of sulfur formation/removal and constant oxygen evolution.
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