The Coulombic Nature of Active Nitrogen Sites in N-Doped Nanodiamond Revealed In Situ by Ionic Surfactants

The surface activity and charged nature of ionic surfactants (sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB)) are used as in situ probes for the Coulombic nature of active sites in N-doped nanocarbon. In this report, we demonstrate that, by selectively masking charge-carrying sites, the active nitrogen sites in N-doped nanodiamond for oxygen reduction reaction are positively charged moieties, rather than those uncharged or negatively charged groups. From the N group analysis by X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption in a hydrogen gas atmosphere (H2-TPD), we put forth the concern that the active nitrogen groups in N-doped nanocarbon may contain oxygen and should not be simply classified by the four conventional nitrogen types by XPS binding energy.