Fabrication of dog-bone shaped Au NRcore–Pt/Pdshell trimetallic nanoparticle-decorated reduced graphene oxide nanosheets for excellent electrocatalysis

Abstract

Herein, a wet-chemical synthetic approach has been adopted, taking advantage of electrostatic interactions between positively charged [CTA]⁺ capped Au NRs and negative functionalities of graphene oxide (GO), to fabricate dog-bone shaped Au NR_core–Pt/Pd_shell decorated reduced graphene oxide (rGO) nanosheets (GMTs) for efficient ethanol electrooxidation reaction (EOR). This new strategy is based on an exceptionally efficient immobilization of trimetallic nanoparticles onto rGO sheets. It is important to note that the sequential addition of Pt and Pd precursor salts into the reaction mixture evolves Pd as the surface layer in the trimetallic assembly (described as GMT-1), whereas reversal of the sequence of addition results in spongy Pt NPs at the outer surface (designated as GMT-2), and thus two different types of Au_core–Pt/Pd_sandwich–Pd/Pt_shell nanoparticle-decorated rGO nanocomposites have been fabricated. The well recognized electrocatalytic performance of Pt is improved towards EOR by controlled assembling of Au and Pd in the rGO support in both the GMTs, exceeding the performance of the corresponding bimetallic composites. The presence of Pd and rGO decreases the CO poisoning of Pt and rGO supports restrict the aggregation of the nanoparticles during CV cycles. Thus the durability of the GMT catalysts has been improved in contrast to other related materials. Interestingly, the exposed spongy Pt NPs, present at the exterior of the trimetallic particles in GMT-2, help to exhibit better EOR activity (∼1.22 times) but lower durability (∼10%) in comparison to its analogue, GMT-1. The observed electrocatalytic efficiencies of GMTs are superior to commercial Pt/C (more than 6 times better mass utilization and ∼40% higher durability) and most of the recently reported related materials, which suggest cost-effective and efficient practical fuel cell application of GMTs.