Degradation cyclic voltammetry measurements

On the basis of theoretical calculations Chance et al. [203] have interpreted electrochemical measurements using a scheme similar to that of MacDiarmid et al. [181] and Wnek [169] in which the first oxidation peak seen in cyclic voltammetry (at approx. + 0.2 V vs. SCE) represents the oxidation of the leucoemeraldine (1 A)x form of the polymer to produce an increasing number of quinoid repeat units, with the eventual formation of the (1 A-2S")x/2 polyemeraldine form by the end of the first cyclic voltammetric peak. The second peak (attributed by Kobayashi to degradation of the material) is attributed to the conversion of the (1 A-2S")x/2 form to the pernigraniline form (2A)X and the cathodic peaks to the reverse processes. The first process involves only electron transfer, whereas the second also involves the loss of protons and thus might be expected to show pH dependence (whereas the first should not), and this is apparently the case. Thus the second peak would represent the production of the diprotonated (2S )X form at low pH and the (2A)X form at higher pH with these two forms effectively in equilibrium mediated by the H+ concentration. This model is in conflict with the results of Kobayashi et al. [196] who found pH dependence of the position of the first peak. 

Cell degradation results in performance loss of the fuel cell. Appropriate measurement techniques are required in order to characterize the cell and determine the prevaihng degradation process. Cyclic voltammetry (CV) is a common diagnostic tool for the characterization of electrochemical cells [18, 58). With respect to PEM-FCs, it provides information about the electrochemical active area, the double-layer characteristics, and the hydrogen fuel crossover through the membrane. 

Surface area loss of eathode platinum due to catalyst agglomeration was also detected by transmission electron microscopy (TEM) analysis and cyclic voltammetry. The behaviors of both eleetrodes were measured and anode degradation eould be attributed to the high anode potential. Fuel starvation eaused severe and permanent damage to the eleetroeatalysts of the PEMFC. 

Organic compounds were added to 0.05mol dm at 1, 10, and lOOmmol dm , and the change of the ORR current was evaluated as the measure of the ORR degradation in the presence of organic impurities. Cyclic voltammetry was performed to obtain the platinum active surface from the hydrogen adsorption/ desorption peaks. 

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