Electrode parasitic anodic reaction

Electrochemical Reaction/Transport. Electrochemical reactions occur at the electrode/electrolyte interface when gas is brought to the electrode surface using a small pump. Gas diffuses through the electrode structure to the electrode/electrolyte interface, where it is electrochemically reacted. Some parasitic chemical reactions can also occur on the electrocatalytic surface between the reactant gas and air. To achieve maximum response and reproducibility, the chemical combination must be minimized and controlled by proper selection of catalyst sensor potential and cell configuration. For CO, water is required to complete the anodic reaction at the sensing electrode according to the following reaction ... 

For undivided cells, a valid alternative is provided by the stirred tank reactor (STR), which is characterized by a high flexibility in the use of different electrode structures and shapes. The adoption of a sacrificial anode (Gennaro et al. 2004) and/or specific fluidodynamic conditions (He et al. 2004a) avoids most of the drawbacks connected with parasitic electrode reactions. 

If ambient air is used, the presence of water vapor leads to a side reaction forming LiOH (2Li + 2H2O 2LiOH + H2, theoretical potential 2.08 V). This reaction may lead to irreversible processes in the anode and a decreasing performance of the system. Hence, attempts have been made in order to exclude water vapor from the electrode. By using a non-aqueous electrol3 e, the parasitic reactions can be avoided and alleviate the safety concerns. 

In a fuel cell, the difference in reactant gas compositions at the two electrodes leads to the formation of a difference in Galvani potential between anode and cathode, as discussed in the section Electromotive Force. Thereby, the Gibbs energy AG of the net fuel cell reaction is transformed directly into electrical work. Under ideal operation, with no parasitic heat loss of kinetic and transport processes involved, the reaction Gibbs energy can be converted completely into electrical energy, leading to the theoretical thermodynamic efficiency of the cell. 

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