Tuning the dimensions and structures of nitrogen-doped carbon nanomaterials derived from sacrificial g-C3N4/metal–organic frameworks for enhanced electrocatalytic oxygen reduction

Abstract

Here we demonstrate a facile strategy for tuning the dimensions and structures of nitrogen-doped carbon nanomaterials via regulating the ratio of Co/Zn in zeolitic imidazolate framework (ZIF) arrays in situ grown on g-C₃N₄ nanosheets, followed by a pyrolysis process. One-dimensional nitrogen-doped bamboo-like carbon nanotube encapsulated Co nanoparticle (Co/N-BCNTs), two-dimensional nitrogen-doped carbon nanosheet (N-CNS) and three-dimensional nitrogen-doped carbon nanotube framework encapsulated Co nanoparticle (Co/N-CNTFs) electrocatalysts are successfully fabricated from Zn/Co-ZIF@g-C₃N₄, ZIF-8@g-C₃N₄ (Co free) and ZIF-67@g-C₃N₄ (Zn free), respectively. The resulting Co/N-BCNTs electrocatalyst exhibits a better oxygen reduction reaction (ORR) activity than the other two catalysts, with a half-wave potential of 0.83 V (versus the reversible hydrogen electrode) in alkaline solutions, which is superior to that of a commercial Pt/C catalyst. More importantly, the Co/N-BCNTs show much higher stability and better methanol-tolerance than the Pt/C catalyst in a 0.1 M KOH solution. It has been demonstrated that the enhanced catalytic performance of Co/N-BCNTs is attributed to their suitable surface area, well-dispersed N dopants, and Co encapsulated inside carbon nanotubes. The presented strategy offers new prospects in developing highly active electrocatalysts.