Impedance Analysis of PdCo as Cathode for PEM Fuel Cells

In this work the oxygen reduction reaction (ORR) on PdCo particles (~ 11 nm) supported in carbon Vulcan XC-72 is analyzed. In 0.5 M H2SO4/O2 the impedance spectra showed one or two time constants, the first time constant was associated to the reduction of O2 to H2O, while the second, to the reduction from H2O2 to H2O. By using electric circuits, the kinetics parameters of ORR were obtained. The values of charge transfer resistance Rct1 obtained from the impedance spectra were used to determine the kinetic parameters (b, α and i0) of ORR. The impedance spectra of PEMFC fed with H2/air and H2/O2 allows determining the values of Rc; with these, the values of b, α, and i0 were calculated. The values of i0, are related to the kinetics of ORR on PdCo/C, the highest value of i0 belongs to the PEMFC fed with H2/O2.