Microwave plasma synthesized nitrogen-doped carbon nanotubes for oxygen reduction

Abstract

Nitrogen-doped carbon nanotubes (NCNTs) with nitrogen content of 5.38 at% were successfully synthesized via microwave plasma chemical vapor deposition (MPCVD) technique employing methane and ammonia as precursors. Their high defective and abundant nitrogenous functional groups of superficial structures had been verified and considered to be closely related to their oxygen reduction reaction (ORR) activity. The influence of their structural features on ORR activity in alkaline electrolyte was studied in detail. The electrochemical analysis shows promoted crossover resistance and long-term stability, and comparable electrocatalytic activity of NCNTs with Pt-CNTs, suggesting that the ORR activity of NCNTs has been greatly promoted on account of nitrogen doping. The highest ORR performance was obtained with the loading of 729 μg cm−2, indicating initial potential of 0.87 V versus reversible hydrogen electrode (RHE) and n of 4.1, which are comparable with Pt-CNTs. Such excellent ORR performances of NCNTs obtained in this paper reveal the superiority of low-temperature plasma technique to synthesize favorable NCNTs for oxygen reduction.