Kinetics of oxygen reduction reaction on Corich core-Ptrich shell/C electrocatalysts

The nanostructured Corich core-Ptrich shell/C electrocatalysts were prepared by combining the thermal decomposition and the chemical reduction methods. The particle size of homemade Corich core-Ptrich shell/C analyzed by TEM was significantly greater than that of Pt grain size calculated from the XRD data due to the existence of Co in core. The mass activity and specific activity of oxygen reduction reaction (ORR) at the overpotential (η) of 0.1 V were 6.69 A g−1 and 1.51 × 10−5 A cm−2 for Pt/C, and 10.22 A g−1 and 2.73 × 10−5 A cm−2 for Corich core-Ptrich shell/C in 0.5 M HClO4 aqueous solution at 25 °C. The Tafel slopes of ORR on Pt/C and Corich core-Ptrich shell/C electrocatalysts were obtained as 64 and 67 mV dec−1 at a lower η (50–100 mV), and 116 and 110 mV dec−1 at a higher η (120–200 mV). The exchange current densities of ORR on Pt/C and Corich core-Ptrich shell/C evaluated based on the higher Tafel slope regions were 6.76 × 10−5 and 9.21 × 10−5 A cm−2, respectively. The experimental results indicated that the ORR on Corich core-Ptrich shell/C electrocatalyst in 0.5 M HClO4 aqueous solution was a four electron transfer mechanism and first order with respect to the dissolved oxygen.