Porous Carbon Nanosheets Derived from ZIF-8 Treated with KCl as Highly Efficient Electrocatalysts for the Oxygen Reduction Reaction

Developing advanced electrocatalysts for the oxygen reduction reaction (ORR) is a critical reaction in fuel cells. Metal-organic framework (MOF)-derived nitrogen-doped carbons have been widely reported as promising electrocatalysts for ORR. Herein, a KCl-assisted pyrolysis method is reported to prepare N-doped porous carbon nanosheets (NCNS). During pyrolysis preparation, KCl crystals act as templates and activator, penetrating the ZIF-8-derived carbon material via capillarity, which facilitates the formation of micro- and mesopores carbon nanosheets. By adjusting the KCl dosage and pyrolysis temperature, the carbon material structure, nitrogen species, and graphitization degree are effectively controlled. The optimal NCNS-10-900 catalyst exhibits a higher half-wave potential (approximate to 0.88 V) in alkaline solution, which is even better than Pt/C (approximate to 0.86 V). The NCNS-10-900 also exhibits outstanding long-term stability with an only 17 mV shift in half-wave potential after a 10K cycle durability test. All of these high properties are ascribed to the high specific surface area, the abundant microporous and mesoporous nanosheet structure, and the synergistic effects of the N species with intrinsic activity. This strategy of using a KCl-assisted pyrolysis MOF provides a feasible method to explore highly efficient and robust non-noble metal catalysts for energy-conversion reactions.

Automated summary

The nitrogen-doped porous carbon nanosheets prepared by KCl-assisted pyrolysis exhibit controlled carbon material structure and enhanced catalytic performance for the oxygen reduction reaction, with higher half-wave potential and outstanding long-term stability.