Electrode service life

The electrode service life is strongly dependent on the current density used. A simple model relating the service fife to the current density (i) has been obtained (Chen et al. 2001) ... 

To achieve a catalytic layer on base materials is the core process for DSA-electrode fabrication. To ensure the layer stability, it is important to try to make the layer better adhesion with the base surface. We have tried several methods in the electrode preparation, including pretreatment, pyrolysis technologies, and electrodeposition. Till now, our research revealed that the electrode service life and the behaviors have been influenced by the electrode preparation methods and technological factors. 

Development of new accelerated tests for the estimation of electrode service life for the wastewater under investigation. 

As an example. Fig. 20-7 shows potential and protection currents of two parallel-connected 750-liter tanks as a function of service life. The protection equipment consists of a potential-controlled protection current rectifier, a 0.4-m long impressed current anode built into the manhole cover, and an Ag-AgCl electrode built into the same manhole [10,11]. A second reference electrode serves to control the tank potential this is attached separately to the opposite wall of the tank. During the whole of the control period, cathodic protection is ensured on the basis of the potential measurement. The sharp decrease in protection current in the first few months is due to the formation of calcareous deposits. 

The network of lead wires must provide optimum mechanical support to the pellets of active material that fill the void space. Sufficient conductivity has also to be provided by the grid. Grids for positive and negative electrodes are usually similar. In batteries designed for extended service life, the positive grid is made heavier to provide a corrosion reserve. For very thin electrodes, a lead foil is used as the substrate and current conductor. 

Figure 9 illustrates the consequences for battery practice. The above penetration rate would reduce the cross—section of a grid spine in a tubular electrode by about 50% within the usual service life of 15 years. This result is confirmed by field experience and shows that long-life batteries must have a corresponding "corrosion reserve" in their positive grids. 

We consider that the practical electrode s efficiency at operation under high current density conditions and during service life is determined by the state of the particles of conductive additive s surface. With reference to this, we can point out two main factors effecting fundamentally reliable operation of the NiOx electrode. 

It can be clearly seen from the curves presented for TEG (Figure 1) that there is not any evidence for the electrode surface oxidation, at least during the first Nstabie =190 cycles, whereas the oxygen evolution rate is quite high under these conditions. After 190 cycles a gradual decrease of peak currents can be noticed (see curves corresponding to 200 and 250 cycles, respectively). The service life of the electrode composed of TEG under these conditions is Nmax=250 cycles. 

When cycling a NGF electrode under the same conditions (Figure 2), the deintercalation peak current values are much higher. At the same time, under comparable conditions, a noticeable surface oxidation of NGF starts to be observed significantly earlier, after Nstable = 50-60 cycles. The service life of the NGF electrode is Nmax =100 cycles. 

Sputter-ion pumps of the triode type excel in contrast to the diode-type pumps in high-noble gas stability. Argon is pumped stably even at an inlet pressure of 1 10 mbar. The pumps can be started w/ithout difficulties at pressures higher than 1 10 mbar and can operate continuously at an air inlet producing a constant air pressure of 5 10 mbar. A new kind of design for the electrodes extends the service life of the cathodes by 50 %. 

Electrolyzers with membranes jtennitting an easy passage of current had an advantage over the bell-type electrolyzers because the electrodes could be set closer together so that a somewhat higher current density could be used. Apart from this, the electrolyzer v as of simple design attendance and operational control was easy so that one mail per shift could be left in charge of the whole plant. One drawback, however, was the short service life of the membrane. 

Ways of improving these anodes are now being investigated in many laboratories and it has been demonstrated that the service life of Sb-doped Sn02 electrodes... 

Cardarelli, E, Taxil, P., Savall, A., Comninellis, C., Manoli, G. and Leclerc, O. (1998), Preparation of oxygen evolving electrodes with long service life under extreme conditions. J. Appl. Electrochem., 28(3) 245-250. 

Mraz, R. and Krysa, J. (1994) Long service life Ir02/Ta205 electrodes for electroflotation. J. Appl. Electrochem. 24, 1262-1266. 

Content of Sb in the crystals of Sn02. Proper doping of Sb can increase the conductivity and also the electrocatalytic ability of the Sn02 electrodes. Usually the behavior of the electrode do not vary much more when Sb content lies in 3-6%. But higher or smaller doping can decrease the service life of the electrode. 

Although Sn02 electrode possesses better electrocatalytic ability for organic degradation, a most important problem for the Sn02 electrode is its shorter service life... 

The service life is defined as the time the electrode can be used without eletrocat-alytic ability descending. The value can be got by an intensive experiment at larger electric current with the formula below... 

The radius of Ru atom is in the middle of that of Sn atom and Ti atom. The three elements can form stabilized solid solution during thermal oxidation and it can resist the formation of nonconductive Ti02. That is the reason why Sn02 electrode with interlayer processes longer service life. Ru02 coating has low oxygen evolution potential, which will result in low electrocatalytic... 

SEM or TEM is a useful tool to investigate the micrograph of the electrodes surfaces. The image of the electrode can give us some information about the coating quality and implied some service-life information. For those nanometers, they also can imply some information about the crystal sizes. 

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