Pd–Co nanoparticles decorated on different carbon based substrates as electrocatalyst for O2 reduction reaction

In this study, a facile process for the synthesis of bimetallic Pd–Co nanotubes on multi-walled carbon nanotubes (MWCNTs) and chemically reduced graphene oxide (rGO) is reported. The synthesized nanocatalysts are characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX). Catalysts are evaluated for the oxygen reduction reaction (ORR) in basic media. The electrocatalytic performance of Pd–Co supported on rGO and MWCNTs toward ORR is compared with bimetallic and single Pd nanoparticles decorated on Vulcan carbon (XC-72R) by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and rotating disk electrode (RDE) in 0.1 M NaOH solution. The specific electrochemical surface areas of Pd–Co supported on rGO is higher than the corresponding carbon-supported Pd nanoparticles (222.09 vs. 41.57 m² g⁻¹, respectively). The RDE results confirm that the final product of the oxygen reduction is water and the proposed main path is direct 4 electron transfer process with smooth transfer kinetic rate on the Pd–Co/rGO in comparison to Pd–Co/C. Furthermore, the lower charge transfer resistance of the particles in ORR process for the Pd–Co/rGO compared to single Pd/C catalyst, indicating it could be excellent candidate for ORR in alkaline media.