Novel Fe₃C Nanoparticles Encapsulated in Bamboo-Like Nitrogen-Doped Carbon Nanotubes as High-Performance Electrocatalyst for Zinc-Air Battery

Abstract

In this paper, a novel material of Fe3C nanoparticles encapsulated inside the bamboo-like nitrogen-doped carbon nanotubes (Fe3C@b-NCNTs) is synthesized by pyrolysis of the mixture of iron salt and melamine-formaldehyde resin/SiO2 hybrid, and explored as the electrocatalyst for air-cathode of zinc-air battery. The morphology, structure and composition of Fe3C@b-NCNTs samples obtained at three different heat-treatment temperatures (700 °C, 800 °C, and 900 °C, respectively) are characterized by SEM, TEM, HR-TEM, HAADF-STEM, XRD, XPS, Raman and BET. Through electrochemical measurements using cyclic voltammetry, linear sweep voltammetry, and chronoamperometry, the oxygen reduction reaction (ORR) performance of such catalysts are evaluated. The obtained Fe3C@b-NCNTs-800 shows high and even better activity and stability than Pt/C catalyst. The excellent ORR performance of such catalyst can be ascribed to the bamboo-like nanotube structure, the adequate nitrogen doping level, and the synergistic effect between graphitic carbon layer and Fe3C nanoparticles. It is believed that the graphitic carbon layers can prevent Fe3C nanoparticles from agglomeration and protect Fe3C nanoparticles against electrolyte corrosion, while Fe3C nanoparticles activate the neighboring graphitic carbon layers and thus boost ORR activities. A rechargeable home-made zinc-air battery (ZAB) is assembled by using this catalyst for air cathode. The high performance of the assembled ZAB suggests that this Fe3C@b-NCNTs-800 catalyst is a promising electrcatalyst for metal-air batteries.