Graphene-Supported ' Core-Shell 'Ł Carbon Nitride Fe- and Sn-Based Electrocatalysts for the Oxygen Reduction Reaction (ORR)
In this study, new "Pt-free" electrocatalysts are prepared and studied for the ORR process. These ECs consist of alloyed Fe-Sn nanoparticles embedded in a carbon nitride “shell” a few nanometers thick, supported on conducting micrometric graphene sheets that act as the “core”. The electrocatalytic precursors are prepared by a sol-gel/gel-plastic process following a protocol previously developed in our laboratory ; afterwards, they undergo suitable pyrolysis and activation processes. The proposed electrocatalysts, both pristine (e.g., FeSn0.5-CNl 900/Gr) and activated (e.g., FeSn0.5-CNl 900/Gra) are extensively characterized in order to gain a full understanding of their structural features, proprieties and electrocatalytic performance . The chemical composition is determined by inductively-coupled plasma atomic emission spectroscopy (ICP-AES). The structure is elucidated by powder X-Ray diffraction (XRD); the morphology is inspected by high-resolution scanning electron microscopy (HR-SEM) and high-resolution transmission electron microscopy (HR-TEM) (Fig. 1). Finally, “ex situ” cyclic voltammetry with the rotating ring-disk electrode (CV-TF-RRDE) and “in situ” single fuel cell measurements are carried out to evaluate the electrocatalytic performance as well as to study the ORR mechanism. The preliminary CV-TF-RRDE investigations in an alkaline medium exhibit promising results. Indeed, the catalysts exhibit an overpotential ca. 70 mV higher with respect to a 20 wt.% Pt/C reference (Fig. 2).
The authors would like to thank the European Union for the financial support provided by the GRAPHENE Flagship, project “GRAFUS - Graphene and related materials as supports for innovative metal carbon nitride electrocatalysts for anion-exchange membrane fuel cells”.
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