Rationale approach of nitrogen doping at defect sites of multiwalled carbon nanotubes: A strategy for oxygen reduction electrocatalysis

A development of electrocatalyst for oxygen reduction reaction (ORR) is one of the crucial reactions for low temperature fuel cell applications. The state-of-the-art catalyst (platinum based) have various limitations such as low abundance, extortionate price and sensitive towards impurities. Therefore, design of high performance non-platinum electrocatalyst is the most challenging issue for low temperature fuel cell. In this work, we discuss the nitrogen doping at defect sites of multiwalled carbon nanotubes (MWCNTs) using melamine foam as a template for efficient CNT assembly with subsequent role of different nitrogen containing agents such as melamine and hexamine. Templated assembly of functionalized CNT through melamine foam provides easy approach towards nitrogen doping that followed effective exposure of active sites (like pyridinic-N and oxidic-N) for electroreduction of oxygen. As-prepared N-CNT catalysts (prepared using both the precursors) show better ORR activity than Pt/C in alkaline medium. A sharp reduction peak in their cyclic voltammogram under O-2-saturated 0.1 M KOH solution proves their activity towards ORR electrocatalysis. More interestingly, the onset potentials of -0.92 V and -1.1 V versus RHE for N-CNT obtained by hexamine and melamine respectively indicate superior onsets than that of Pt/C (-1.04 V vs RHE). Furthermore, the best N-CNT catalyst (obtained by melamine) reveals better stability up to 15,000 cycles than Pt/C with zero response towards methanol, exhibiting an excellent methanol tolerance. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, nitrogen-doped multiwalled carbon nanotubes (N-CNTs) were prepared using melamine foam as a template to address the challenges of platinum-based catalysts for oxygen reduction reaction in low temperature fuel cells. The N-CNT catalysts showed superior ORR activity and stability compared to Pt/C, with onset potentials indicating better performance. The use of melamine as a precursor resulted in the best performing N-CNT catalyst with excellent methanol tolerance.