Pyrolysis of conjugated nanoporous polycarbazoles to mesoporous N-doped carbon nanotubes as efficient electrocatalysts for the oxygen reduction reaction

Abstract

Developing new techniques for the synthesis of N-doped carbon nanotubes (N-CNTs) with high porosities and abundant N-doped active sites is significant for energy conversion and utilization. We report herein a novel non-CVD methodology that exploits a conjugated-nanoporous-polymer-driven, self-templated route toward a new family of highly N-doped carbon nanotubes. The utilization of a task-specific tubular nanoporous polycarbazole as a template maintains both high porosity and density of N-doped active sites, while simultaneously affording a hollow nanotube-like morphology of the final N-doped carbons. Attributed to these unique functionalities, the resultant N-CNT-based electrocatalyst exhibits a superior oxygen reduction reaction (ORR) activity with a half-wave potential of 0.88 V (vs. the reversible hydrogen electrode), higher long-term stability, and better methanol tolerance than commercial 20% Pt/C in alkaline media. More importantly, the ORR performance in an acidic medium exceeds that of the most previously reported non-precious carbonaceous catalysts. These findings could provide an alternative approach towards highly efficient non-precious N-CNT-based electrocatalysts for the ORR.