Facile preparation of N-doped hierarchically porous carbon derived from pitch-based hyper-cross-linked polymers as an efficient metal-free catalyst for oxygen-reduction

Abstract

Pitch, as a by-product of the petroleum and coal chemical industry, is in great need of improving its potential value by expanding its application areas. Using low-cost and available carbon precursors and facile preparation to design and prepare metal-free electrocatalysts with preeminent performance and high stability for oxygen reduction reaction (ORR) have become a research trend. Herein, we combine the above-mentioned requirements to prepare a kind of N-doped hierarchical porous carbon materials as ORR electrocatalysts using pitch-based hyper-cross-linked polymers (PHCPs) as carbon precursors by a simple ammonia activation process. Under the optimized pyrolysis temperature (900 °C), the optimal N-PHCP-900 owns high specific surface area of 999 m2 g−1, hierarchical pore structure, plentiful accessible active N and high density of defects. Benefitting from these special advantages, the N-PHCP-900 exhibits an outstanding ORR property with a positive half-wave potential (0.883 V vs. RHE) and robust durability in alkaline electrolyte, which surpass those for commercial Pt/C and the majority of non-noble metal electrocatalysts. Therefore, this work not only offers a novel paradigm in the development of affordable and efficient metal-free ORR electrocatalysts as the hopeful candidate, but also explores a feasible method for realizing the high value-added application of pitch.