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

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/Fe3C 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 Fe3C@C/CNT hybrid materials by catalytic pyrolysis of lignite using KOH and FeCO3. The structural characteristic of Fe3C@C/CNT hybrid materials is that Fe3C 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 m2 g–1). We discussed the effects of KOH, FeCO3, and melamine in the catalytic pyrolysis of lignite to produce Fe3C@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 Fe3C is provided by FeCO3. (3) The aggregation of Fe into large and irregular Fe nanoparticles is inhibited by melamine, which facilitates the generation of Fe3C. When the Fe3C@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.