Oxygen reduction reaction characteristics

In this section, we summarize the kinetic behavior of the oxygen reduction reaction (ORR), mainly on platinum electrodes since this metal is the most active electrocatalyst for this reaction in an acidic medium. The discussion will, however, be restricted to the characteristics of this reaction in DMFCs because of the possible presence in the cathode compartment of methanol, which can cross over the proton exchange membrane. 

If a reaction path is predominant and one of its elementary step is rate determining, the Tafel slope will be characteristic of this step. Thus, electrochemical measurements performed on rotating disk electrode can provide a first solution to elucidate the mechanistic behavior of oxygen reduction reaction on a catalyst. Par-sons has demonstrated that, in a several step electrode process,... 

Wang W, Huang Q, Liu J, Zou Z, Zhao M, Vogel W, Yang H (2009) Surface and stmcture characteristics of carbon-supported Pd3Ptl bimetallic nanoparticles for methanol-tolerant oxygen reduction reaction. J Catal 266 156-163... 

Oxygen Reduction Reaction in Acid Solution, Table 2 Structural and electrochemical characteristics of the Pd/C and Pd-Fe/C electrocatalysts for ORR in 0.1 mol dm HClOa (From [33]) ... 

Two parts are treated one is the physical and chemical features of materials of molten carbonate fuel cells (MCFCs), and the other is performance analysis with a 100 cm class single cell. The characteristics of the fuel cell are determined by the electrolyte. The chemical and physical properties of the electrolyte with respect to gas solubility, ionic conductivity, dissolution of cathode material, corrosion, and electrolyte loss in the real cell are introduced. The reactirm characteristics of hydrogen oxidation in molten carbonates and materials for the anode of the MCFC are reviewed. The kinetics of the oxygen reduction reaction in the molten carbonates and state of the art of cathode materials are also described. Based on the reaction kinetics of electrodes, a performance analysis of MCFCs is introduced. The performance analysis has importance with respect to the increase in performance through material development and the extension of cell life by cell development. Conventional as well as relatively new analysis methods are introduced. 

Table 2 Characteristics of the oxygen reduction reaction (ORR) and film properties on Nafion -filmed platinum electrodes, in the presence of various kinds of impurity ions...

The activity of oxide catalysts in general declines as reduction proceeds. Characteristic of the processes that involve lattice oxygen is that the initial activity (i.e. that measured by the first pulse) approaches that in the presence of oxygen, while the selectivity is either identical in the presence or absence of oxygen, or higher in the latter case, because side reactions due to adsorbed oxygen are excluded. The rate at which the activity falls during reduction is dependent on both the nature of the catalyst and on the process studied. After a certain initial activity decrease, often a lower, but rather constant, activity level is reached. 

Combustion is an oxidation-reduction reaction between a nonmetallic material and molecular oxygen. Combustion reactions are characteristically exothermic (energy releasing). A violent combustion reaction is the formation of water from hydrogen and oxygen. As discussed in Section 9.5, the energy from this reaction is used to power rockets into space. More common examples of combustion include the burning of wood and fossil fuels. The combustion of these and other carbon-based chemicals forms carbon dioxide and water. Consider, for example, the combustion of methane, the major component of natural gas ... 

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