▎ 摘　　要

We report that hydrogenation of mono-, bi-, and trilayer graphene samples via exposure to H(2) plasma occurs as a result of electron irradiation of H(2)O adsorbates on the samples, rather than H species in the plasma as reported by [Elias et al., Science 323, 610 (2009)]. We propose that the hydrogenation mechanism is electron-impact fragmentation of H(2)O adsorbates into H(+) ions. At incident electron energies >60 eV, we observe hydrogenation that is significantly more stable at temperatures >200 degrees C than previously reported. (C) 2010 American Institute of Physics. [doi:10.1063/1.3524517]