Spectra and the Virtual Anode

DMFC Physical and Operation Parameters Used in the Calculations 

50 mA cm arise due to conversion of the permeated methanol close to the membrane. In other words, the MOR-dominating part serves as a virtual anode within the CCL, which converts the incoming methanol flux into a proton current. This proton current is then converted to water flux in the ORR-dominating part of the CCL, adjacent to the GDL. 

FIGURE 5.20 The MOR and ORR rates and the local proton current density in the half of the CCL, adjacent to the membrane, for the indicated molar concentrations of methanol feed. The shaded region indicates the virtual anode. The cell current density is fixed at 50 mA cm . Each frame shows the ORR and MOR reaction rates and the proton current density (dashed line) at the methanol concentration of (a) 0.5 M, (b) 1 M, and (c) 1.5 M. 

FIGURE 5.21 Calculated impedance spectra of the CCL for the indicated methanol molar concentrations. The semicircles intercept is at 12 Hz for 1 M curve, and at 0.153 Hz for 1.5 M curve. 

FIGURE 5.22 Measured impedanee spectra of the DMFC cathode for the indicated methanol molar concenlrations. (Data from Piela, R, Fields, R., and Zelenay, P. 2006. J. Electrochem. Soc., 153, A1902-A1913.) 

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