Cathode oxygen pressure

From the measured cathodic oxygen pressures and decomposition potentials, metallic sodium cannot be formed. Consequently, the primary product is Na[W03]4-However, for the melt composition considered here the bronze NUjWOj obtained corresponds to an x value of 0.5 (see Fig. 1, 16.3.2.3.2). Although kinetic studies do not permit a complete interpretation subsequent loss of WO3 from Na[W03]4 is the probable mechanism. 

Zhang, J.X., Thampan, T., Datta, R. 2002. Influence of anode flow rate and cathode oxygen pressure on CO poisoning of proton exchange membrane fuel cells. /. Electrochem. Soc. 149 A7GS-72. 

Reduction of oxygen is one of the predominant cathodic reactions contributing to corrosion. Awareness of the importance of the role of oxygen was developed in the 1920s (19). In classical drop experiments, the corrosion of iron or steel by drops of electrolytes was shown to depend on electrochemical action between the central relatively unaerated area, which becomes anodic and suffers attack, and the peripheral aerated portion, which becomes cathodic and remains unattacked. In 1945 the linear relationship between rate of iron corrosion and oxygen pressure from 0—2.5 MPa (0—25 atm) was shown (20). 

In operation, the fuel flows over the anode and reacts with oxide ions arriving from the electrolyte. Oxygen flows over the cathode where it is reduced and transported as ions from the high oxygen pressure cathode region to the low oxygen pressure anode region. The cell reactions depend upon the fuel. Typically these are... 

Figure 6-7 Effect of CO2/O2 Ratio on Cathode Performance in an MCFC, Oxygen Pressure is 0.15 atm (20, Figure 5-10, Pgs. 5-20)...

Fig. 3.1 Polarization curves of a DEEC at 80 °C (open symbols) and 90 °C (closed symbols). Anodes PtSn/C (triangles) and PtRu/C (squares). Cathodes Pt/C in both cases. Catalyst loading on all electrodes 1 mg/cm. Membrane Nafion 117. Ethanol concentration and flow rate 1 M and 3 mL/min. Oxygen pressure and flow rate 1 atm and 0.4 L/min...

At the cathode, the oxygen electrode, there is a high oxygen pressure and oxygen is reduced by electrons from the cathode conductor to oxide ions, which are then taken up by the lattice of the electrolyte and diffuse to the other electrode, the anode, where they are used to burn the fuel. The oxide ion concentration gradient over the thickness of the electrolyte drives the oxide ions from the cathode to the anode. At the anode the oxide ions oxidize the fuel and leave the electrons on the cathode conductor. The potential over the cell (between the cell electrodes) is proportional to the difference between the oxygen potentials on the two electrodes ... 

However, the physical nature of all processes contributing to the overall polarization loss of the cell still has to be identified. As a consequence, a series of 300 impedance measurements were performed, in which only one parameter at a time was varied cathodic oxygen partial pressure, anodic hydrogen/water partial... 

Figure 16.15 Characteristic dependence of fitted equivalent circuit elements on the cathodic oxygen partial pressure. The dashed line indicates the model prediction according to Eq. (16.17) [pH20(a ode) = 0.625 atm (balance H2),T= 800 °C] (cell Zl 153).

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