Bimetallic Pd–Fe Supported on Nitrogen-Doped Reduced Graphene Oxide as Electrocatalyst for Formic Acid Oxidation

This study was conducted to exploit the properties of nitrogen-doped reduced graphene oxide (N-rGO) as support material for formic acid fuel cell. Nitrogen-doped reduced graphene oxide was synthesized by the hydrothermal synthesis method using graphene oxide (GO) flakes and urea as a nitrogen source. Palladium and iron with controllable atomic ratio were used as the active metals. Graphene oxide and carbon nanotube-supported PdFe nanoparticles were synthesized for comparison. The structure, morphology, and chemical composition of the synthesized catalysts were ascertained by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The average particle sizes for Pd₃Fe/N-rGO and Pd/N-rGO were 4.65 and 3.95 nm, respectively. The electrochemical characterizations (CO stripping, cyclic voltammetry, and chronoamperometry) showed that the Pd₃Fe/N-rGO electrocatalyst had higher electrocatalytic activity and stability compared with that of Pd₃Fe/rGO and Pd₃Fe/CNT. The mass activity of Pd₃Fe/N-rGO in 0.5 M of HCOOH and 0.5 M of H₂SO₄ solutions was 1463.9 mAmg⁻¹ Pd, which was 3.3 and 1.35 times that of the activity obtained with graphene oxide and carbon nanotubes with the same composition, respectively. The superior performance of the Pd₃Fe/N-rGO catalyst was ascribed to the presence of nitrogen functionalities in the nitrogen-doped reduced GO and the synergistic interaction between Pd and Fe nanoparticles. Nitrogen-doped reduced GO promoted the formation of smaller and narrowly distributed nanoparticles and exerted favorable electronic effects because of electron transfer from N to Pd. Therefore, Pd₃Fe/N-rGO can serve as a potential electrocatalyst for the oxidation of formic acid.