  High-quality nitrogen-doped graphene on nickel is prepared by exploiting both
the catalytic properties of nickel and the solubility of nitrogen atoms into
its bulk. Following the standard chemical vapor deposition procedure, a
previously nitrogen-doped nickel substrate is exposed to carbon-containing
precursors so that nitrogen atoms, segregating to the surface, remain trapped
in the growing graphene network. Morphological and chemical characterization by
scanning tunneling microscopy and X-ray photoelectron spectroscopy demonstrates
that the process yields a flat, wide, continuous nitrogen-doped graphene layer.
Experimental results are combined with a thorough density functional theory
investigation of possible structural models, to obtain a clear description at
the atomic scale of the various configurations of the nitrogen atoms observed
in the graphene mesh. This growth method is potentially scalable and suitable
for the production of high-performance nano-devices with well-defined nitrogen
centers, to be exploited as metal-free carbon-based catalysts in several
applicative fields such as electrochemistry, energy storage, gas
storage/sensing or wastewater treatment.
