Graphene supported Pd–Cu bimetallic nanoparticles as efficient catalyst for electrooxidation of methanol in alkaline media

Abstract

Interfacing non-noble metals with noble metal is considered to be the best strategy to balance efficient adsorption and corresponding electrochemical oxidation of fuel relevant for fuel cell reactions. Herein, copper is interfaced with palladium and deposited onto a reduced graphene oxide (RGO) support by employing a simple one-pot chemical reduction using combined advantages offered by l-ascorbic acid and ethylene glycol. Morphological features and elemental composition of Pd–Cu bimetallics on RGO are assessed by transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). The results revealed presence of well-dispersed Pd–Cu particles with an average particle size from 4 to 6 nm on RGO supports (Pd–Cu/RGO). From X-ray photoelectron spectroscopy (XPS) analysis it is understood that Pd–Cu/RGO catalyst owns metallic palladium surface state with a small fraction of CuO or Cu2O species. Methanol electro-oxidation reaction (MOR) is carried out in nitrogen-saturated solution containing KOH (1 M) + CH3OH (1 M) at room temperature on Pd–Cu/RGO, Pd/RGO and Pd/C commercial catalyst. Electrochemical activity descriptors suggest that compared with Pd/RGO and commercial Pd/C (20 wt%), bimetallic Pd–Cu/RGO exhibited 2.1 and 4.0 times higher Jmass, respectively indicating the advantage of interfacing copper with palladium in improving the kinetics of methanol electro-oxidation. The simple synthesis strategy demonstrated here is convenient to extend to fabricate other metallic particles with controlled particle sizes for fuel cell catalytic applications.