Shape-Directed Growth of Palladium Nanocubes over Nitrogen-Doped Reduced Graphene Oxide: A Simple Approach for the Fabrication of an Efficient and Durable Electrocatalyst for Formic Acid and Methanol Oxidation Reactions

Herein, we report a simple and highly reproducible synthetic strategy for the shape-directed growth of palladium (Pd) nanocubes supported over nitrogen-doped reduced graphene oxide (NrGO). Characterization of the Pd/NrGO composite by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDXA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy suggests that the composite has a uniform distribution of nanocube-shaped Pd clusters (with an average size of 8.14 nm) firmly anchored to the NrGO matrix. Cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were used to test the electrocatalytic performance and electrochemical stability of the Pd/NrGO composite toward the formic acid oxidation reaction (FAOR) and methanol oxidation reaction (MOR). The Pd/NrGO composite exhibits a better peak current density of 2.6 mA/cm2 (FAOR) and 2.2 mA/cm2 (MOR) as against commercial Pd/C (0.76 mA/cm2 for the FAOR, 1.6 mA/cm2 for the MOR) and Pt/C (0.63 mA/cm2 for the FAOR, 1.5 mA/cm2 for the MOR) with a much lower overpotential requirement for the onset of both the FAOR and MOR. The presented results clearly suggest that the electrochemical stability and electrocatalytic performance of the Pd/NrGO composite crafted for the present work are sufficient to qualify it as a promising alternative of Pt-based anode materials for commercially relevant DFAFCs and DMFCs.