Oxygen reduction reaction operated on magnetically-modified PtFe/C electrocatalyst

Electrocatalytic activity for oxygen reduction reaction on magnetically modified PtFe/C catalysts was investigated. X-ray powder diffraction (XRD) revealed that while the as-prepared PtFe/C catalysts were face-centered cubic (f.c.c), the as annealed catalysts at 700° for 3 h were face-centered tetragonal (f.c.t). Post-heating transformed the as-prepared catalysts from superparamagnetic into ferromagnetic materials as was measured by vibrating sample magnetometer (VSM). Electrochemical results obtained by rotating disk electrode (RDE) technique showed that oxygen reduction reaction took place by an overall four electron charge transfer process. Polarization curves showed that the electrocatalytic activity on ferromagnetic catalyst for oxygen reduction obviously outperformed the as-prepared paramagnetic catalyst. The values of kinetic parameters for the as-prepared and as-heated catalysts were obtained from linear-line region of mass-transfer-corrected Tafel plots. The catalytic enhancement by the magnetically modified catalyst was explained by the magnetic attractive force toward oxygen thus increasing electrochemical flux at the heterogeneous catalytic interface.