The chemical reactivity of single layers of supported graphene (G) is affected by the nature of the underlying substrate: in particular CO chemisorption occurs on G/Ni(111), while graphene on Cu is inert. Here, we demonstrate experimentally that doping of the G layer with nitrogen atoms further increases the reactivity of the G/Ni( 111) system towards CO. The doped layer is obtained by sputtering pristine G/Ni(111) with N-2(+) ions. For an similar to 11% dopant concentration, an additional electron energy loss at 238 meV appears in the HREEL spectra besides the loss around 256 meV present also on pristine G/Ni(111). The new feature corresponds to a CO species with a higher desorption temperature and, consequently, a higher adsorption energy than the one forming on pristine G/Ni( 111). At low coverage, the adsorption energy is estimated to be 0.85 eV/molecule. (C) 2017 Elsevier B.V. All rights reserved.