Cathodic potential, disadvantage

When a poised potential is used, energy is put into the system. For example, if the working potential for the anode was -0.3 V but the potential was poised at 0.2 V, then the input power would be P = 0.5 /, where I is the current achieved in the experiment. Thus, power is input into this system directly in a non-sustainable manner, as opposed to indirectly using the chemical energy of catholytes such as ferricyanide. Another potential disadvantage of this set up is that H2 gas produced in the cathode chamber. If this gas diffuses back into the anode chamber, it can become another substrate for the bacteria which can artificially raise the Coulombic efficiency or power production. 

The Zinc-air battery is more expensive than the dry cell and deteriorates relatively quickly once it is exposed to air. High capacity and a cell potential that does not vary with use offset these disadvantages. Like the dry cell, a zinc-air battery uses zinc for the anode reaction. Uniquely among batteries in common use, this battery relies on molecular oxygen from the atmosphere for its cathode reaction. 

For recycling to improve the performance of an MCFC network, it must provide benefits that outweigh its inherent disadvantages. If carbon dioxide is not separated from the anode-anode recycle, the concentration of carbon dioxide in the anode is increased. This reduces the Nemst potential. The Nemst potential is similarly reduced by the anode-cathode recycle if steam is not condensed out, since recycled steam dilutes reactant concentrations in the oxidant. In addition, part of the power generated by the network is consumed by the equipment necessary to circulate the recycle streams. Such circulation equipment, along with the additional ducting required by recycling, also increases the capital cost of the MCFC network. 

An important aspect of cathodic protection is the means to monitor the effectiveness and the criteria for protection. Criteria recommended by NACE (RP0169-96) for the CP of steel and cast iron piping are given in Table 4 [24]. Although several criteria are described for CP of steel structures, the most commonly used criterion is that the steel structure to be protected should be maintained at a potential more negative than —0.85 V versus Cu/CuSOr reference electrode. The primary disadvantages of this criterion are no connection of the potential of the steel to the corrosion rate, and a large difference in protective... 

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