N-doped carbon nanotubes as an efficient electrocatalyst for O2 conversion to H2O2 in neutral electrolyte

Abstract

The electrocatalytic two-electron oxygen reduction reaction (2e⁻ ORR) is an attractive alternative to the industrial anthraquinone method for on-site direct hydrogen peroxide (H₂O₂) production under ambient conditions. However, identifying cost-effective, active, and selective catalysts for the 2e⁻ ORR still remains a great challenge. Here, a metal-free catalyst (nitrogen-doped carbon nanotubes) is developed for high-efficiency electrochemical H₂O₂ generation in neutral electrolyte (0.1 M phosphate buffered saline (PBS)), enabling a broad green route for practical applications. The as-fabricated nitrogen-doped carbon nanotube (N-CNT) electrocatalyst exhibited a high H₂O₂ selectivity > 90% at a wide range of potentials, as well as superior long-term stability with a remarkable productivity of 4.45 mmol h⁻¹ L⁻¹. Impressively, an unprecedented onset potential for O₂-to-H₂O₂ conversion is achieved at only 0.73 V versus the reversible hydrogen electrode (RHE) in 0.1 M PBS, surpassing those of most catalysts for the 2e⁻ ORR. Furthermore, density functional theory calculations demonstrate that the pyrrolic-N moiety is responsible for the enhanced 2e⁻ ORR performance.