Fe₃C@C/CNT Hybrids Derived from Catalytic Pyrolysis of Lignite: Electrocatalysts for OER

Abstract

Using lignite as the raw material to prepare a new OER catalyst, and thus to make high-value use of lignite and to meet the research and development needs for new energy materials at the same time, a novel Fe/Fe 3 C active species has been reported as a promising catalyst to replace precious metals. In this study, we developed a facile method for the preparation of Fe 3 C@C/CNT hybrid materials by catalytic pyrolysis of lignite using KOH and FeCO 3 . The structural characteristic of Fe 3 C@C/CNT hybrid materials is that Fe 3 C nanoparticles are encapsulated in carbon layers and carbon nanotubes, forming a special core−shell structure. The prepared materials have good graphitization and a large specific surface area (957 m 2 g −1 ). We discussed the effects of KOH, FeCO 3 , and melamine in the catalytic pyrolysis of lignite to produce Fe 3 C@C/CNT materials:(1) Lignite can be catalyzed by KOH to generate carbon nanotubes and porous structures. (2) The transformation of carbon matrix to graphitic carbon is catalyzed and the Fe source for Fe 3 C is provided by FeCO 3 . (3) The aggregation of Fe into large and irregular Fe nanoparticles is inhibited by melamine, which facilitates the generation of Fe 3 C. When the Fe 3 C@C/CNT hybrid is used as an OER catalyst, the OER overpotential is only 407 mV at a current density of 10 mA cm −2 in an alkaline electrolyte, which has great application potential. This work is conducive to improving the economic benefits of lignite and provides a new idea for the high value-added utilization of lignite.