A fast method to prepare Pd-Co nanostructures decorated on graphene as excellent electrocatalyst toward formic acid oxidation

Abstract

The electrochemical reduction of cobalt (II) formate on graphene/glassy carbon electrode (G/GCE) surface in HCl (5 wt%) is used to prepare Pd-Co electrocatalyst. The Pd-Co nanostructures decorated on the graphene nanosheets were prepared in two steps: (1) electrochemical reduction of cobalt (II) formate and (2) the galvanic replacement reaction between Co and Pd2+. This approach has a number of advantages including being environmentally friendly, simple, low-price, and very fast. The morphology and bulk compositions of the samples were investigated via Field Emission Scanning Electron Microscopy (FESEM), X-ray diffraction (XRD) patterns, Energy Dispersive X-ray Spectroscopy (EDS). Electrochemical techniques, including Cyclic Voltammetry (CV), Chronoamperometry (CA) and Electrochemical Impedance Spectroscopy (EIS) measurements were used to analyze the electrochemical activity of the samples. The peak current density for oxidation of formic acid on Pd-Co/G electrocatalyst was very high (151.32 mA cm−2). The Pd-Co/G increased the current density 7.1 times more than Pd/C. Besides, the onset oxidation potential and peak potential for Pd-Co/G electrocatalyst illustrated a negative shift in comparison to Pd/C. Chronoamperometry experiment showed that the stability of the Pd-Co/G catalyst was remarkably promoted. The Pd-Co/G electrocatalyst represents extraordinary electrocatalytic activity and durability toward formic acid oxidation.