Techniques Used in Electrocatalytic O2 Reduction Reactions

The most frequently used techniques for ORR catalysis studies are steady-state polarization, cyclic voltammetry, rotating disk electrode (RDE), and rotating ring-disk electrode (RRDE). 

Polarization means that the potential of the electrode surface shifts away from its equilibrium value, leading to an electrochemical reaction. In general, for an elementary electrochemical reaction, O + e - R, the polarization follows the Butler-Volmer equation [3]  

MEA active area 4.4 cm. Hj/Air gases with 100% relative humidity, adapted from [4], (Reprinted from Electrochimica Acta, 52(7), Song C, Tang Y, Zhang J, Zhang J, Wang H, Shen J, et al, PEM fuel ceU reaction kinetics in the temperature range of 23-120 °C, 2552-61. 2007, with permission from Elsevier.) 

Cyclic voltammetry is the most useful technique in electrochemistry. It can quickly provide qualitative information about catalysts and electrochemical reactions, such as the electrochemical response of catalysts and flic catalytic activity of the catalysts wifli respect to some electrochemical reactions. The principles of this technique have been discussed in detail in other chapters. Here, we simply look at the application of the technique in ORR catalyzed by surface adsorbed catalysts. 

The peak currents of the wave of Fe(III)/Fe(II) increase linearly with the potential scan rate, which is a typical feature of the reaction of an electrode surface adsorbed redox couple. From the slope, the electron number can be calculated according to the following equation [3, 9]  

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