Fe-carbon nitride "Core-shell" electrocatalysts for the oxygen reduction reaction. (20th December 2016)

• Record Type: Journal Article
• Authors: Vezzù, Keti; Bach Delpeuch, Antoine; Negro, Enrico; Polizzi, Stefano; Nawn, Graeme; Bertasi, Federico; Pagot, Gioele; Artyushkova, Kateryna; Atanassov, Plamen; Di Noto, Vito
• Is Part Of: Electrochimica acta. Volume 222(2016)
• Page Start: 1778
• Page End: 1791
• Publication Date: 2016-12-20
• Subjects: Fe-carbon nitride based electrocatalysts -- Fe-N-C Platinum Group Metal-free catalysts -- Oxygen reduction reaction -- "Core-shell" morphology -- Powder X-ray diffraction -- CV-TF-RRDE method; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2016.11.093
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: In this report, the preparation of Fe-carbon nitride (CN)-based electrocatalysts (ECs) with a "core-shell" morphology for the oxygen reduction reaction (ORR) is described. The ECs consist of spherical XC-72R carbon nanoparticles, the "cores", that are covered by a CN matrix, the "shell", that embeds Fe species in "coordination nests" . The latter consist of hollow cavities in the CN matrix, whose internal surface is covered by N- and C-ligands able to stabilize alloy nanoparticles or active sites. Two families of CN-based ECs are prepared, which are grouped on the basis of the concentration of N atoms in the CN "shell" . Each group comprises of both a "pristine" and an "activated" EC; the latter is obtained from the "pristine" EC by a suitable series of treatments (A ) devised to improve the ORR performance. The chemical composition of the CN-based ECs is determined by Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and microanalysis. The thermal stability under both inert and oxidizing atmospheres is gauged by High-Resolution Thermogravimetric Analysis (HR-TGA). The structure is probed by powder X-ray diffraction, and the morphology is inspected by Scanning Electron Microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM). The surface area of the CN-based ECs is determined by nitrogen physisorption techniques, and the surface composition is probed by X-ray Photoelectron Spectroscopy (XPS). The electrochemical performance and reaction mechanism of the CN-based ECs in the ORR is investigated in both acid and alkaline environments by cyclic voltammetry with the Thin-Film Rotating Ring-Disk Electrode setup (CV-TF-RRDE). The influence of the preparation parameters and of the treatments on the physicochemical properties, the ORR performance, and reaction mechanism is studied in detail. In the alkaline environment the FeFe2 -CNl 900/CA "core-shell" EC shows a remarkable ORR onset potential of 0.908 V vs. RHE which, with respect to the value of 0.946 V vs. RHE of the Pt/C ref., classifies the proposed materials as very promising "Platinum Group Metal-free" ECs for the ORR.