Efficiency and Thermodynamics
Electrocatalytic analyzes will often mention the current efficiency or faradaic efficiency of a given process determined by a bulk electrolysis experiment. For example if one molecule of hydrogen results from every two electrons inserted into an acidic solution then the faradaic efficiency would be 100%. This indicates that the electrons did not ended up performing some other reaction. For example the oxidation of water will often produce oxygen as well as hydrogen peroxide at the anode. Each of these products is related to its own faradaic efficiency which is tied to the experimental arrangement.
Nor is current efficiency the same as thermodynamic efficiency, since it never address the how much energy (potential in volts) is in the electrons added or removed. The voltage efficiency determined by the reactions overpotential is more directly related to the thermodynamics of the electrochemical reaction. In fact the extent to which a reaction goes to completion is related to how much greater the applied potential is than the reduction potential of interest. In the case where multiple reduction potentials are of interest, it is often difficult to set an electrolysis potential a "safe" distance (such as 200 mV) past a redox event. The result is incomplete conversion of the substrate, or else conversion of some of the substrate to the more reduced form. This factor must be considered when analyzing the current passed and when attempting to do further analysis/isolation/experiments with the substrate solution.
Read more about this topic: Bulk Electrolysis
Famous quotes containing the words efficiency and and/or efficiency:
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