▎ 摘　　要

We investigate hydrogen adsorption effects on stabilities and electronic properties of nitrogen defects in graphene using first-principles electronic-structure calculations within the density-functional theory. We find that the adsorption of hydrogen atoms on the pyridine-type nitrogen defects in graphene becomes energetically favorable, whereas in the case of the substitutional nitrogen defect the hydrogen adsorption becomes unfavorable. We also find that a transition from p-type to n-type doping properties occurs by hydrogen adsorption on the pyridine-type defects, suggesting that even the carrier type is controllable in nitrogen-doped graphene. (C) 2014 AIP Publishing LLC.