Nitrogen-Doped Carbon Nano-Onions as a Metal-Free Electrocatalyst

Growing environmental and economical concern necessitates novel materials with inherent electrochemical activity in as-prepared. Herein, we report, the electrochemical reactivity of the nitrogen-doped carbon nano-onions (N-CNO) prepared by a simple flame pyrolysis method. The as-obtained N-CNO has high N-content (4 at.%) and a large Brunauer-Emmett-Teller surface area (842.3 m2 g−1). The as-prepared N-CNO were probed as a cathode material for the oxygen reduction reaction (ORR) and as an electrocatalyst for sensitive nitrite (NO2−\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\mathrm{NO}}_2^{-} $$\end{document}) determination. The results demonstrate that, compared to N-CNT, as-prepared N-CNO exhibit a significantly enhanced ORR activity in alkaline medium and long-term stability with negligible change in activity. The N-CNO-based electrochemical nitrite sensor exhibits nitrite oxidation with two linear ranges 0.5 to 10 μM (R = 0.996) and 10 to 1000 μM (R = 0.978) with a sensitivity of 811.22 and 400.51 μA mM−1 cm−2, respectively. The detection limit (LOD) was 0.3 μM. The relative standard deviation (RSD) for eight replicate determinations was found to be 2.53%. The values of observed analytical parameters (linear range, sensitivity, and LOD) are comparable or superior to previously reported carbon-based NO2−\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\mathrm{NO}}_2^{-} $$\end{document} sensors.