▎ 摘　　要

In this work, graphene for use as methane (CH4) sensors has been designed and evaluated via first-principles theory. Firstly, the effect of the number of layers of graphene on methane adsorption is investigated. The results show that the methane adsorption will be increased with the number of layers, the maximum energy is 0.267 eV. Furthermore, the adsorption of CH4 leads to a small opening of the band structure of graphene. As for the doping (Al-doped) in graphene, we mainly focus on the concentration of Al atoms. The Al atom was found to cause a huge increment in methane adsorption energy that can be up to 3.212 eV when the concentration of Al atoms is 5.555%. Meanwhile, the doping of Al atoms also enhances the conductive properties of graphene. Lastly, the effect of defects was also investigated. While slightly smaller than that of pristine graphene, the methane adsorption energy of defected graphene is also increased with the number of layers. It was found that the model with the methane on the top of the empty atom and the H atoms on the top of the center of the carbon ring results in the best methane adsorption. (C) 2017 Published by Elsevier Ltd.