Performance comparison of graphene and graphene oxide-supported palladium nanoparticles as a highly efficient catalyst in oxygen reduction

In this work, the performance of graphene nanosheets (GNs) and graphene oxide (GO) nanosheets, as a support for palladium nanoparticles (PdNPs) toward oxygen reduction reaction (ORR), was studied. The graphene nanosheets were functionalized by a new and simple method. The PdNPs were synthesized on a glassy carbon electrode (GCE) modified with GNs or GO via a potentiostatic method; without using any templates, surfactants or stabilizers. The surface morphology of the modified electrodes was studied by scanning electron microscopy, energy dispersive X-ray and X-ray diffraction techniques. Cyclic voltammetry and rotating disk electrode (RDE) voltammetry methods were used for calculation of electrochemical parameters of the ORR. The GCE modified with PdNPs-GO exhibited a higher catalytic activity in comparison with PdNPs-GNs toward ORR. The high electrocatalytic activity of PdNPs-GO/GCE was attributed to oxygen-containing groups that were formed on the GO during functionalization of graphene nanosheets. These groups act as anchoring sites for metal nanoparticles and improve their dispersion on GO nanosheets. Also, mechanism of ORR was intensively investigated and transferred electron numbers in reaction was calculated using RDE data analysis. Finally, stability of the modified electrodes was studied and the results confirmed that the GCE modified with PdNPs-GO has a long-term stability.