Cathodic electron acceptance

The underlying theory may be simplified as follows. Polarography is concerned with electrode reactions at the indicator or micro-electrode, i.e. with reactions involving a transfer of electrons between the electrode and the components of the solution. These components are called oxidants when they can accept electrons, and reductants when they can lose electrons. The electrode is a cathode when a reduction can take place at its surface, and an anode when oxidation occurs at its surface. During the reduction of an oxidant at the cathode, electrons leave the electrode with the formation of an equivalent amount of the reductant in solution ... 

For redox electron transfer reactions, the transfer of electrons from an electrode to an oxidfmt particle to form a reductant particle is the cathodic reaction (the electron-accepting reduction of oxidants) and the transfer of electrons from a reductant particle to an electrode to form an oxidant particle is the anodic reaction... 

What happens when the moving ions reach an electrode surface If the electrodes are inert, which means that they don t react chemically with the ions in the solution, then only electron transfer will take place at the electrodes. Electrons are being pumped from the battery toward the cathode, where reduction will occur. At the cathode, the ion that reacts is the one that most readily reacts with electrons. In Figure 17.3, Na and Cl are both present in the liquid near the surface of the cathode. Na+ accepts electrons more readily, so each Na cation gains one electron, being reduced to the metal. 

Electrons are delivered (cathode) or accepted (anode) by the electrode. At electrodes with a small area (<0.1 cm ) the electrolysis can be conducted on a microscale. From the current/voltage curves obtained, valuable information can be obtained with regard to the reaction conditions for carrying out preparative scale electrolysis. The electrolysis is conducted in a cell, which is equipped with three electrodes ... 

Logically, the ionic current that flows through the soil has to be converted to an electronic current carried by the electrons through the electrodes and the external wires that connect this electrical circuit to the power supply. This change occurs at the electrode/electrolyte interface in the electrode wells. An electrochemical reduction reaction takes place at the cathode, which accepts electrons from the external... 

For case 2, the rate of the overall reactions will be controlled by electron acceptance at the cathode site, which is small due to the covering of scales. Thus, the electron flow will be slow, and the current density at the anode will be very low. Hence, there will be low corrosion penetration at the anode. This shows the safety in the use of cathodic inhibitors. 

The syntheses and properties of different polymers containing high electron affinity CF3 and oxadiazole groups have been reviewed. It has been shown that when CF3 groups are incorporated into conjugated polymers, such as poly(phenylene vinylene) derivatives, the polymers with CF3 substituents show better electron accepting properties. This makes it possible to use stable aluminum in place of air sensitive calcium as metal cathode in polymer LEDs. 

The carboxylate substituents on the phenylene in 162 (Scheme 77) produce a red shift in the PL (A-max = 443 nm) but a drop in PL efficiency (20% versus 78-81% for 156) [259]. Jen and coworkers have prepared the copolymers 163 (kmax = 447 nm) and 164 (kmax = 477 nm) with electron-accepting dicyanobenzene units by Suzuki polycondensations [267]. The alternating copolymer 163 shows only marginally higher EL efficiency than the PDAF homopolymer 85 (0.057% versus 0.044%), but the other copolymer 164 with only 25% of dicyanobenzene units (m = n) shows an EL efficiency over 10 times higher (0.50%) in double-layer devices with a PEDOT holetransporting layer and calcium cathodes [267]. 

In essence, all that is required for electrochemistry is two electrodes, the oxidizing electron-accepting anode and the reducing electron-donating cathode. 

Electrodes coated with 26 dispersed in the interior of poly(V-vinylcarbazole) exhibit very similar stable cyclic voltammograms (Fig. 22b, c) The 26 forms conducting pathways in the polymer and is not molecularly dispersed. Additionally, films of polymeric Pcs 12 (prepared by method B 2) exhibit a similar electrochemical behaviour i2ib, c. 248) jjjg peak potentials shift in the cathodic direction (Fig. 22). The outstanding electrochemical properties of the films of 12 and 26 appear to be due to a combination of the high conductivity, also in the neutral state (Table 4), and the electron-accepting... 

The interpretation of the above equations indicate that an anodic reaction, which is equivalent to what is known as oxidation, loses ze metal electrons and the cathodic reaction accepts or gains ze electrons for reducing pertinent ions. Consequently, both anodic and cathodic reactions are coupled in a corrosion process. Adding eqs. (1.1a) and (1.1b) yields eq. (1.1c). Thus, REDOX (RED = reduction and OX = oxidation) is the resultant reaction equation, eq. (1.1c), and represents the overall reaction at equUibiium where the anodic and cathodic reaction rates are equal. Observe that the anodic reaction is also referred to as an oxidation reaction since it has lost ze electrons, which has been gained by the cathodic reaction for producing sulfuric acid H SOa)- Thus, a cathodic reaction is equivalent to a reduction reaction. Furthermore, The arrows in eq. (1.1) indicate the reaction directions as written and they represent irreversible reactions. On the other hand, a reversible reaction is represented with an equal sign. Thus, the metal reaction can proceed to the right for oxidation or to the left for reduction as indicated by eq. (1.2)... 

The sodium and hydrogen ions At the cathode, hydrogen ions are attracted to the cathode. The accept electrons more readily chloride and hydroxide ions are than sodium ions do. They attracted to the anode. become atoms, then form... 

The electrolyte thus formed can conduct electric current by the movement of ions under the influence of an electric field. A cell using an electrolyte as a conductor and a positive and a negative electrode is called an electrolysis cell. If a direct-current voltage is appHed to a cell having inert electrode material such as platinum, the hydrogen ions (cations) migrate to the cathode where they first accept an electron and then form molecular hydrogen. The ions... 

Batteries are rated by ampere-hours, which is the total amount of charge that can be delivered. More specifically, it is a measure of the number of electrons that can be released at the anode and accepted at the cathode. It is also related to the energy content or capacity of the batteiy. If a battery has a capacity of 90 A-h, it can supply a current of 90 A for one hour, 30 A for three hours, or 1 A for 90 hours. The gi eater the current, the shorter the period the battery can supply It likewise, the less the current, the longer the period the battery can supply it. 

Electron Acceptor a species in solution that accepts one or more electrons from a cathode for each act of the cathodic reaction and is thus reduced to a lower valence state. 

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