Facile and scalable synthesis of coal tar-derived, nitrogen and sulfur-codoped carbon nanotubes with superior activity for O2 reduction by employing an evocating agent

Since heteroatom-doped carbon nanomaterials were proved to be one of the most promising alternatives to noble metal platinum-based cathode electrocatalysts in fuel cells over the past years, considerable efforts have been devoted to promoting their practical application. Although much progress has been made, the large- scale practical application of these heteroatom-doped carbon nanomaterials is presently inaccessible due to the lack of a facile synthesis method and low-cost heteroatom precursors with broad sources. Herein, we used the cost-effective, nitrogen (N) and sulfur (S)-containing coal tar which has an abundant supply of N and S precursors to synthesize value-added N and S-codoped carbon electrocatalysts for the oxygen reduction reaction (ORR) by employing the evocating agent of dicyandiamide (DICY). The results demonstrated that DICY could effectively help coal tar to form N and S-codoped carbon nanotubes (NS-CNTs) on the surface of CoCl2 nanoparticles. The as-synthesized NS-CNTs exhibited highly comparable ORR activities to commercial Pt-C catalysts in both acidic and alkaline media. This report not only provides a novel, facile and scalable approach for the preparation of low-cost CNT electrocatalysts with superior ORR activities but also offers a new and clean-utilizing path for the harmful N and S elements in coal tar and helps to reduce environmental pollution.