Abstract
In this work, bimetallic PdxCoy nanoparticles supported on nitrogen-doped reduced graphene oxide catalysts were synthesized and tested for formic acid oxidation as potentially efficient and durable electrocatalysts. Graphene oxide was nitrogen doped through hydrothermal chemical reduction with urea as a nitrogen source. The PdxCoy nanoparticles were deposited on the nitrogen-doped graphene oxide support using the impregnation-reduction method with sodium borohydride as a reducing agent and sodium citrate dihydrate as a stabilizing agent. The structural features, such as phases, composition, oxidation states, and particle sizes, of the nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy–energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The Pd nanoparticle sizes in Pd1Co1/N-rGO, Pd/N-rGO, and Pd1Co1/CNT were 3.5, 12.51, and 4.62 nm, respectively. The electrochemical performance of the catalysts was determined by CO stripping, cyclic voltammetry, and chronoamperometry. Pd1Co1/N-rGO showed the highest mass activity of 4833.12 mA–1 mg Pd, which was twice that of Pd1Co1/CNT. Moreover, Pd1Co1/N-rGO showed a steady-state current density of 700 mA–1 mg Pd after 5000 s in chronoamperometry carried out at +0.35 V. Apart from the well-known bifunctional effect of Co, nitrogen-doped graphene contributed to the performance enhancement of the Pd1Co1/N-rGO catalyst.
Highlights
Fuel cells have gained significant attraction as a sustainable and clean source of energy
The overall performance of Direct formic acid fuel cells (DFAFCs) depends on the thermodynamics and kinetics of anodic and cathodic reactions, the formic acid oxidation (FAO) reaction at the anode is usually the limiting reaction [6]
The X-ray diffraction (XRD) spectrum for the synthesized catalysts was generated to identify the chemical nature of phases and the crystalline size
Summary
Fuel cells have gained significant attraction as a sustainable and clean source of energy. Vulcan carbon is the most widely used support in PEM fuel cells It shows a low surface area, a large proportion of micropores, an inert chemical structure, and corrosion in acidic and alkaline environments [13]. Nitrogen-doped reduced graphene oxide (N-rGO) facilitates the nucleation and growth behavior of nanoparticles, which causes an improved distribution of metal nanoparticles on the support [23,24,25,26]. Reported that nitrogen-doped reduced graphene oxide plays a vital role in improving the performance of supported PdCu nanoparticle catalysts for FAO. PdCo nanoparticles supported on nitrogen-doped reduced graphene oxide electrocatalysts for FAO have not been reported so far. The present work aimed to synthesize nitrogen-doped reduced graphene oxide using graphene oxide as a precursor and evaluate its performance as a support material of Catalysts 2021, 11, 910.
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