Oxidation at anodes

It is basically irrelevant in steady-state measurements in which direction the polarization curves are recorded that is, whether the potential is moved in the direction of more positive (anodic scan) or more negative (cathodic scan) values. But sometimes the shape of the curves is seen to depend on scan direction that is, the curve recorded in the anodic direction does not coincide with that recorded in the cathodic direction (Eig. 12.3). This is due to changes occurring during the measurements in the properties of the electrode surface (e.g., surface oxidation at anodic potentials) and producing changes in the kinetic parameters. 

Liquid mercury is quite easily oxidized at anodic potentials (when immersed in water) so most of the measured current would be due to the reaction Hg -> Mercury is electrochemically stable for a... 

The electrode behavior of silicon in nonaqueous solvents strongly depends on the presence of water. The presence of a very small amount of water will cause the formation of silicon oxide at anodic potentials and cause reduction of water at large cathodic potentials. The presence of a thin oxide layer due either to native oxide or to water presence affects the electrode behavior by acting as a physical barrier and source of interface states. It has been found that with 10 ppm water in organic electrolytes the silicon surface is oxidized slowly via formation of oxide islands which grow to 0.6 nm thick and cover about 60% of the surface after 1 week of immersion. 

Synthesis of conductive polymers can be realized either by addition of oxidizing agents or by electrochemical oxidation at anodic potentials. To distinguish from electrochemical polymerization, polymerization by external oxidizer is often marked in literature as a chemical polymerization. Many types of conductive polymers formed by this way have a strong trend to adsorb on the surfaces... 

Any type of fuel cell is based on a redox reaction in which a fuel is oxidized at anode side by an oxidant which is reduced at the cathode side. The result is the production of an electronic flow through an external circuit, together with chemicals and heat, while the presence of the electrolyte permits the electric circuit to be closed inside the cell. Several types of fuel cells can be today used for many applications, and they differ in dependence of the nature of the electrolyte, which determines the operative range of the cell, and then the type of used fuel. In particular, the most used fuel is hydrogen thanks to its high reactivity also at... 

Only weakly electropositive metals can, obviously, be purified by electrorefining, since the concerned metal must not react with water and must be easily oxidized (at anode) and reduced (at cathode) relative to hydrogen. Beside copper, some other metals for which electrorefining has been employed are Silver, gold, tin and lead. In the electrolytic purification of these metals the relevant electrolyte is the one listed below against each metal ... 

Bhardwaj et al. [2] studied by in-situ real-time STM imaging the passivation of polycrystalline iron in borate buffer. They proceeded by alternating oxidation steps at increasing anodic potentials and reduction steps at cathodic potential. After reduction of the natural oxide at ftie cathodic potential, relatively flat surfaces were produced supposedly corresponding to the metal substrate. Upon oxidation at anodic potential, rougher surfaces were at first produced, with patches or clusters of nanometer dimensions. These patches were observed in the first image after the oxidation step. 

PT conducting films can be generated through electrochemical polymerization of thiophene, where the monomer is oxidized at anodic potentials. Thiophene shows an oxidation potential peak of Eqx = 1.6 V ca. vs SCE (CH3CN + 10 M N(Bu)4C104 + 10 M thiophene sweep rate 20 mV/s H2O 10 mol 1 ) [38] this means that poly(thiophene) can be oxidized to anodic potentials and deposited on an electrode. 

Direct methanol fuel cell is an electrochemical device that converts the chemical energy of a reaction directly into electrical energy. The principle and schematic diagram of a DMFC is shown in Figure 9.1. In a typical DMFC, methanol and water molecules are simultaneously electro-oxidized at anode to produce CO2, electrons, and protons through the reaction (methanol oxidation reaction, MOR) ... 

Eiectrodeposition runs parallel with the process of electrolysis. Redox reactions taking place in the bath solution simultaneously result in the metal deposition on the cathode, also known as the working electrode. Various steps involved in the eiectrodeposition include (i] oxidation at anode on the application of external current, (ii] dissolution of metal ions in electrolyte solution, (iii] metal ion transportation from electrolytic solution to the cathode surface, (iv] reduction of ions at the cathode, and (v] continuous metal layer formation on the cathode surface. The amount of metal deposition depends on deposition time and other parameters determined by Faraday s law, described by the following equation ... 

Table 2. Electrode-catalyst fabrication for methanol electro-oxidation at anode in alkaline condition and techniques used for the analyses of the system... 

The comparison of various techniques used for the analyses of methanol and ethanol electro-oxidation at anode and the results are given in Tables 2 to 3 for methanol and ethanol, respectively. The most commonly used technique in electrochemical studies of fuel cell reactions has been cyclic voltammetry. The cyclic voltammetry is used to study the redox behavior of electrodes in fuel-electrolyte solutions (Bard et al. 2001). The cyclic voltammogram helps to identify the reaction intermediates, poisoning species, reaction mechanism, suitable combination of electrode material and electrolyte/fuel mixtures, such that the formation of poisoning species is prevented. Prabhuram et al. (1998) investigated methanol oxidation on unsupported platinum electrodes in alkaline condition (Table 2). The cyclic voltammograms (CVs) were recorded in... 

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